Wednesday, September 24

1. Finish Law of Conservation of Mass Activity
2. Finish Separating a Mixture Activity
3. Self-study
4. Modules 1 and 2 Test

Tuesday, September 16

1. Significant Figures and Dimensional Analysis Practice Questions
2. Matter and Change Notes

Homework

• Density Lab due Friday, start of class
• Significant Figures Wayground - due Friday, end of class
• Properties of Matter Google Form - due Sunday at 11:59 PM
• Modules 1 and 2 Test on Wednesday, September 24 - a study guide has been posted

​

Have your calculator, chemistry binder, and a pen/ pencil

5001

Wednesday, September 17

1. Density Lab Discussion
2. Properties of Matter Notes
3. Separating a Mixture Notes
4. Law of Conservation of Mass Activity - due end of class today

​

Homework:

• Density Lab due Friday, start of class
• Significant Figures Wayground - due Friday, end of class
• Properties of Matter Google Form - due Sunday at 11:59 PM
• Modules 1 and 2 Test next Wednesday, September 24

Have your chemistry binder and a pen/ pencil

Matter and Change

Vocabulary

Matter is anything that has mass and takes up space

​

Matter that has a uniform and definite composition is called a substance

Scenario

Ms. Long told you all to go to the chemistry lab. Once you all arrive, you stumble upon a mysterious white powder. You have no idea what it is or how it got there.

Scenario

Ms. Long told you all to go to the chemistry lab. Once you all arrive, you stumble upon a mysterious white powder. You have no idea what it is or how it got there.

​

What steps could you take to help you determine the identity of the substance?

Scenario

You take note of the following:

Scenario

You take note of the following:

Physical Properties of Mystery Substance

Physical Properties

A physical property is a characteristic that can be observed or measured without changing the identity of the substance

Physical properties

Intensive properties

Extensive properties

Properties of Matter

Intensive properties do not depend on the amount of matter present

​

Examples - color, hardness, melting point, boiling point, density

Properties of Matter

Extensive properties depend on the amount of matter that is present

​

Examples - volume, mass, the amount of energy

​

Extensive Properties vs. Intensive Properties

Physical Changes

A physical change is a change in a substance that does not involve a change in the identity of the substance

​

States of Matter - Intensive Property

• A change of state is a physical change of a substance from one state to another

​

• Three common states of matter are:
• Solid
• Liquid
• Gas

Solids

Matter in the solid state has definite volume and definite shape

Particles that make up a solid are packed very closely together and are fixed in one position

Liquids

Matter in the liquid state has a definite volume but an indefinite shape

​

Particles in a liquid move around one another freely

​

Gas

Matter in the gas state has neither definite volume nor definite shape

​

As gas particles move, they spread apart, filling the space available

Gas

Vapor describes the gaseous state of a substance that is generally a liquid or solid at room temperature

Chemical Properties

The ability or inability of a substance to combine with or change into one or more other substances is called a chemical property

​

Example: The white powder isn’t flammable and won’t easily catch fire

​

A process that involves one or more substances changing into new substances is called a chemical change (chemical reaction)

Mixtures

Mixtures

A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties

Mixture of rocks, sand, iron, and salt

Mixture silver and mercury

What are two types of mixtures?

​

• Heterogeneous mixtures are NOT uniform throughout
• Example - Clay-water mixture
• Homogeneous mixtures are uniform in composition
• Example - Salt-water solution

Vocabulary

​

• Another name for a homogeneous mixture is a solution

​

Vocabulary

​

An alloy is a homogeneous mixture of metals, or a mixture of a metal and a nonmetal in which the metal substance is the major component

​

Vocabulary

​

• The term phase is used to describe any part of a sample with uniform composition and properties

​

• A homogeneous mixture consists of a single phase
• A heterogeneous mixture consists of two or more phases

Is it homogeneous or heterogeneous?

Salad dressing

Granite

Oolong Tea

Cereal Bar

Soy Sauce

Smog

Is it homogeneous or heterogeneous?

​

Cereal Bar

Is it homogeneous or heterogeneous?

​

Cereal Bar

​

heterogeneous

Is it homogeneous or heterogeneous?

​

Salad Dressing

​

​

​

Is it homogeneous or heterogeneous?

​

Salad Dressing

​

heterogeneous

​

​

Is it homogeneous or heterogeneous?

​

Granite

​

​

Is it homogeneous or heterogeneous?

​

Granite

​

Heterogeneous

​

Is it homogeneous or heterogeneous?

​

Tea

​

​

​

Is it homogeneous or heterogeneous?

​

Tea

​

Homogeneous

​

Is it homogeneous or heterogeneous?

​

Soy Sauce

​

Is it homogeneous or heterogeneous?

​

Soy Sauce

​

homogeneous

​

Is it homogeneous or heterogeneous?

​

Smog

​

Heterogeneous

​

Friday, September 19

1. Review Separation Science Questions
2. Jeopardy Review
3. Work time
1. Law of Conservation of Mass - due end of class
2. Uncertainty in Measurement Wayground - due end of class
3. Properties of Matter Google form - due Sunday at 11:59 PM
4. Modules 1 and 2 Review Packet

​

Modules 1 and 2 Test next Wednesday, September 24

Have your calculator, science binder, and a pen/pencil

Law of Conservation of Mass

During any chemical reaction, the mass of the products is always equal to the mass of the reactants

​

100.0 g

100.0 g

Law of Conservation of Mass

The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved

​

Matter is neither created nor destroyed but it can be transformed

​

System and Surroundings

When studying energy changes, you can define a system as the part of the universe on which you focus your attention

​

Everything else in the universe makes up the surroundings

​

Your task

Law of Conservation of Mass Activity - due end of class today

​

Working in a group of 1-3, read about chemical changes and the law of conservation of mass. Then you and your team will design a closed system to carry out the reaction of baking soda and vinegar.

Friday, September 19

1. Hand in Density Lab
2. Jeopardy Review
3. Work time
1. Significant Figures Wayground - due end of class
2. Modules 1 and 2 Review Packet
3. Properties of Matter Google Form - due Sunday at 11:59 PM
4. Law of Conservation of Mass Lab - due Wednesday, start of class

​

Modules 1 and 2 Test on Wednesday, September 24

​

Quizlet Live

Wednesday, September 13

Have your Computer, Density Lab Worksheet, and Science Folder with you

​

1. Writing a Procedure
2. Density Lab work time - Hard Copy Due Tomorrow
3. If you finish early - Module 2 Quizizz Practice

​

​

Procedure Example

1. Measure the penny.

​

1. Measure the penny.

2. Drop the penny in the water.

1. Measure the penny.

2. Drop the penny in the water.

3. Measure how much the water rose up.

1. Measure the penny.

2. Drop the penny in the water.

3. Measure how much the water rose up.

4. Record this in Data Table 1.

1. Measure the penny.

2. Drop the penny in the water.

3. Measure how much the water rose up.

4. Record this in Data Table 1.

5. Use these values to find the density of the penny.

1. Measure the penny.

2. Drop the penny in the water.

3. Measure how much the water rose up.

4. Record this in Data Table 1.

5. Use these values to find the density of the penny.

6. Record this in Data Table 1.

1. Measure the penny.

2. Drop the penny in the water.

3. Measure how much the water rose up.

4. Record this in Data Table 1.

5. Use these values to find the density of the penny.

6. Record this in Data Table 1.

​

-How would you score this procedure on a scale of 0-6 (0 being the lowest and 6 being the highest)?

-Provide feedback for this procedure and explain why you gave the score you gave.

Friday, September 15

1. Writing a Procedure
2. Density Lab Work Time
3. Start of Period 4 - Turn in Density Lab

Homework:

• Read Module 2 Notes on Google Classroom
• Reading - The Conservation of Matter During Physical and Chemical Changes and Comprehension Questions - due Wednesday start of class
• Properties of Matter Google Form - due Wednesday start of class
• Module 1-2 Test on Monday, September 25

Matter Review

​

Read through these slides on your own and take notes.

Review

In your science notebooks, draw the solids, liquids, gases Venn diagram. Write the letters of each description in the region of the Venn diagram where they belong.

1. Shape is not fixed
2. Fixed shape
3. Volume is not fixed
4. Fixed volume
5. Particles are randomly arranged
6. Particles have a regular pattern
7. Particles move quickly and in all directions
8. Particles move and slide around each other
9. Particles vibrate but cannot move around
10. Example - Pencil
11. Example - Coffee
12. Example - Helium
13. Made up of atoms

Answers

• Shape is not fixed
• Fixed shape
• Volume is not fixed
• Fixed volume
• Particles are randomly arranged
• Particles have a regular pattern
• Particles move quickly and in all directions
• Particles move and slide around each other
• Particles vibrate but cannot move around
• Example - Pencil
• Example - Coffee
• Example - Helium
• Made up of atoms

A

B

C

D

E

F

G

H

I

J

L

K

M

What is matter made of?

• Atom - the smallest unit of an element that keeps the chemical identity of that element

​

Elements

• Element - a pure substance that cannot be broken down into any other substances and is made of one type of atom
• Examples - hydrogen, aluminum, helium

Compounds

• Compound - a substance that can be broken down into simple stable substances
• Each compound is made from the atoms of two or more elements that are chemically bonded

​

​

Carbon dioxide

Water

Molecules

• A molecule is formed when two or more atoms of an element are chemically joined together

​

Carbon dioxide

Water

Mixtures

• Mixture - a blend of two or more kinds of matter, each of which retains its own identity and properties

​

​

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

Think of each circle as an ATOM

Now let’s put the atoms into groups based on color

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

atom

Think of each colored group as an Element.

​

Elements are made of one type of atom.

ELEMENT

ELEMENT

ELEMENT

ELEMENT

There are only 118 Elements that have been discovered so far

Which of the following is NOT an element?

A. C.

​

​

​

B. D.

Which of the following is NOT an element?

A. C.

​

​

​

B. D.

If this is NOT an element, then what is it?

Because this substance contains two or more atoms that are chemically combined, it is a compound.

A molecule is formed when two or more atoms are chemically joined together

MOLECULE

MOLECULE

MOLECULE

MOLECULE

There are two different types of molecules

Compound

Element

Compound

Element

A mixture contains two or more substances that are not chemically combined.

Elements, Compounds, and Mixtures Key

Compounds and Mixtures

Compounds

Compounds

• A compound is made up of two or more different elements that are combined chemically in a fixed ratio

Properties of Compounds

• The properties of a compound are different from those of its component elements

​

Properties of Compounds

• The properties of a compound are different from those of its component elements

Example: Sodium Chloride vs. Sodium and Chlorine

​

Properties of Compounds

• The properties of a compound are different from those of its component elements

Example: Sodium Chloride vs. Sodium and Chlorine

​

​

​

Law of Definite Proportions

• States that a compound is always composed of the same elements in the same proportion by mass, no matter how large or small the sample

​

• The mass of the compound is equal to the sum of the masses of the elements that make up the compound

​

Law of Definite Proportions

• Percent by mass is the ratio of the mass of each element to the total mass of the compound expressed as a percentage

Example - The compound sucrose (also called granulated sugar) is made of carbon, hydrogen, and oxygen. The analysis of 20.00 g of sucrose from a bag of granulated sugar is given below. Note that the sum of the individual masses of the elements found in the sugar equals 20.00 g, which is the amount of the granulated sugar that was analyzed. This demonstrates the law of conservation of mass as applied to compounds: the mass of a compound is equal to the sum of the masses of the elements that make up the compound.

Suppose you analyzed 500.0 g of sucrose from a sample of sugarcane. The percent-by-mass values for the sugarcane are equal to the values obtained for the granulated sugar. According to the law of definite proportions, samples of a compound from any source must have the same mass proportions.

Practice

1. A 78.0 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?

​

• If 3.5 g of element X reacts with 10.5 g of element Y to form the compound XY, what is the percent by mass of element X in the compound? The percent by mass of element Y?

Law of Multiple Proportions

• When different compounds are formed by a combination of the same elements, different masses of one element combine with the same fixed mass of the other element in a ratio of small whole numbers

Law of Multiple Proportions

Copper (Cu) reacts with chlorine (Cl) under different sets of conditions to form two different compounds. The table below provides an analysis of their compositions.

​

Mass ratio of Compound I

​

Mass ratio of Compound II

=

Law of Multiple Proportions

These compounds are called copper (I) chloride and copper (II) chloride. As the law of multiple proportions states, the different masses of copper that combine with a fixed mass of chlorine in the two different copper compounds can be expressed as a small whole-number ratio. In this case, the ratio is 2:1.

​

Mass ratio of Compound I

​

Mass ratio of Compound II

=

2.000

Practice

3. Complete the table. Then analyze the data to determine if Compounds I and II are the same compound. If the compounds are different, use the law of multiple proportions to show the relationship between them.

Compounds

?

Compounds

• Compounds can be broken down by chemical means

?

Compounds

• Compounds can be broken down by chemical means

?

But HOW??

Compounds

?

Compounds

• Generally, compounds that occur naturally are more stable than individual component elements, therefore, separating a compound into its elements often requires external energy, such as heat or electricity

Compounds

• The diagram shows a setup used to produce the chemical change of water into its component elements - hydrogen and oxygen - through a process called electrolysis

• Electrolysis - a process where electricity is used to make a chemical change happen that wouldn’t happen otherwise

Compounds

• One end of a long platinum electrode is exposed to the water in a tube and the other end is attached to a power source

​

• An electric current splits water into hydrogen gas in the compartment on the right and oxygen gas in the compartment on the left

Wednesday, September 27

1. Lab Equipment Blooket
2. Review Mixtures
3. Return Unit 1 Test and Density Lab
4. Work Time
1. Separating a Mixture Lab - due tomorrow

Find your group members from yesterday and answer these questions together.

1. Was the mixture in the lab a heterogeneous mixture or a homogeneous mixture? Explain.

2. How were you able to separate the sand? Explain why the properties of sand allowed you to do this?

3. How were you able to separate the salt and water? What equipment was used?

4. In the solution of salt and water, which is the solute and which is the solvent? Explain.

5. How could you separate a solution of ethanol (a type of alcohol) and water?

Wednesday, September 25

• Lab Equipment Blooket
• Mixtures Notes
• Separating a Mixture Lab - due end of class

​

Homework

• Study Guide and Review Packet have been posted - a key to the packet will be posted on Wednesday after school
• Unit 1 Test on Friday, 9/27

​

How Will Your Team Separate the Different Mixture Components?

How Will Your Team Separate the Different Mixture Components?

How can we separate mixtures?

• Methods used to separate parts of a mixture include:
• Distillation
• Evaporation
• Filtration
• Magnetic attraction

Distillation

• Liquids can be separated by heating them up to the temperature at which one boils.
• The liquid becomes a gas, then the gas cools and forms the separated liquid

Evaporation

• When left in the open air, liquids can change to a gas, leaving the solid components behind

Filtration

• Solids can be separated from liquids by pouring the mixture through a filter

Magnetic Attraction

• Iron objects can be separated from a mixture using a magnet

Chromatography

Chromatography separates the components of a mixture dissolved in either a gas or a liquid (called the mobile phase) based on the ability of each component to travel or be drawn across the surface of a fixed substrate (called the stationary phase)

Homogeneous and Heterogeneous

How would you separate a mixture of mercury and silver?

Pure Substances

• A pure substance has a fixed composition

​

• Pure substances are either compounds or elements

Pure Substances

• Every sample of a given pure substance has exactly the same characteristic properties

​

• Every sample of a pure substance has exactly the same composition
• Example - Pure water is always 11.2% Hydrogen and 88.8% Oxygen

Elements and Compounds

Elements and Compounds Review

• An element is the simplest form of matter that has a unique set of properties

​

• A compound is a substance that contains two or more elements chemically combined in a fixed proportion

Chemical Change

• A chemical change is a change that produces matter with different composition than the original matter

Distinguishing Substances and Mixtures Review

• If the composition of a material is fixed, the material is a substance

​

• If the composition of a material may vary, the material is a mixture

Symbols and Formulas

• Each element is represented by a one- or two- letter chemical symbol

​

• Chemical formulas represent compounds

The Periodic Table - A Preview

• A periodic table is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties

​

• The periodic table allows you to easily compare the properties of one element (or a group of elements) to another element (or group of elements)

The Periodic Table - A Preview

• Each horizontal row of the periodic table is called a period

​

• There are seven periods in the periodic table

The Periodic Table - A Preview

• Each vertical column of the periodic table is called a group or family

​

• Elements within a group have similar chemical and physical properties

Chemical Reactions

Chemical Changes

• The ability of a substance to undergo a specific chemical change is called a chemical property

​

• A chemical property can only be observed when a substance undergoes a chemical change

Chemical Changes

• A chemical change is also called a chemical reaction

​

• One or more substances change into one or more new substances during a chemical reaction

​

Chemical Changes

• A substance present at the start of the reaction is a reactant

​

• A substance produced in the reaction is a product

​

Recognizing Chemical Changes

• Possible clues to a chemical change include:
• A transfer of energy
• A change in color
• The production of a gas
• The formation of a precipitate

Recognizing Chemical Changes

• Transfer of energy

​

• Example - When fireworks burn they give out energy in the form of light, heat, and sound

Recognizing Chemical Changes

• Color change

​

• Example - When a test strip is dipped in a solution, the color change is used to determine the pH of the solution

Recognizing Chemical Changes

• Production of a gas

​

• Example - Bubbles of carbon dioxide gas form when an antacid tablet is dropped into a glass of water

Recognizing Chemical Changes

• A precipitate is a solid that forms and settles out of a liquid mixture

​

• Example - One step in the production of cheese is a reaction that causes milk to separate into solid curds and liquid whey

Friday, September 1, 2023

1. Turn in Signed Syllabus and Lab Safety Contract - due Monday
2. Rules and Expectations
3. Human Bingo
4. Review Summer School Activity
5. Measurements and Calculations Notes

Wednesday, September 3, 2025

• Hand in Lab Safety Contract and Course Syllabus (due Friday)
• Lab Safety - Save Dr. Skelly
• Measurements and Calculations Notes and Practice

Homework:

• Turn in Lab Safety Contract and Course Syllabus - due Friday
• Measurements and Scientific Method Google Form Quiz - due Sunday, 9/7 at 11:59 PM
• Modules 1 and 2 Test on Wednesday, 9/ 24

Have your calculators, computers, and a writing utensil

Friday, September 5

1. Turn in Lab Safety Contract and Course Syllabus - due TODAY
2. Fundamentals of Experimental Design
3. Water Investigation Lab

​

Homework:

• Measurements and Scientific Method Google Form Quiz - due Sunday, 9/7 at 11:59 PM
• Modules 1 and 2 Test on Wednesday, 9/ 24

​

​

​

Have your computer and a writing utensil

​

You will NOT need your calculator today

You want to know how the projectile angle affects the displacement of an object.

You follow the procedure below:

1. Set a protractor on the lab bench.
2. Line up your toy gun with the 0 degree angle.
3. Shoot the toy gun.
4. Using a tape measure, measure and record the displacement of the object.
5. Repeat steps 1-3 with the following angles: 15, 30, 45, 60, 75, and 90 degrees.
6. Complete two trials for each angle.

Identify the independent variable.

Identify the dependent variable.

​

Identify a controlled variable.

Your task

Complete the assignment titled Fundamentals of Experimental Design on Google Classroom.

​

We will go over the answers together.

Let’s go to the lab

You may choose your lab group members (groups of 1-3) but everyone will complete his or her own lab worksheet. Please bring one device per group.

​

​

Post-lab questions

​

1. The less salty the surrounding water, the faster the ice cube will melt. Discussion of data (2)

​

As the ice cube melts in the freshwater, the cold melt water from the ice cube sinks to the bottom of the beaker because it is more dense than the freshwater solution. (1) This forces the warmer, less dense water from the bottom of the beaker to move toward the surface (1). The warmer, less dense water transfers heat to the ice cube, causing it to melt faster. (1)

​

Meanwhile in the saltwater, the cold freshwater from the ice cube floats on top (1) of the saltwater because the saltwater is more dense. (1) Thus the ice cube sits in a pool of cold water, blocking the heat from the saltwater from getting to the ice cube. (1) The evidence becomes more obvious with colored ice.

Amoeba Sisters Lab Safety

What should be done in the following situations?

What should be done in the following situations?

What should be done in the following situations?

What should be done in the following situations?

How should the chemicals in the well plate be disposed?

What should be done in the following situations?

How should the chemicals in the well plate be disposed?

What should be done in the following situations?

How should the chemicals in the well plate be disposed?

What should be done in the following situations?

How should the chemical in the beaker be disposed?

What should be done in the following situations?

How should the chemical in the beaker be disposed?

What should be done in the following situations?

How should the chemical in the beaker be disposed?

water

What should be done in the following situations?

When heating a test tube, where should the open end of the tube be pointed?

What should be done in the following situations?

When heating a test tube, where should the open end of the tube be pointed?

​

​

​

Away from you and others

Lab Equipment and Lab Safety Activity

​

​

Save Dr. Skelly!

This is Dr. Skelly. He’s a friendly biologist about to submit his research to a prestigious journal!

This is Dr. Pollution. He’s Dr. Skelly’s rival!

This is Dr. Skelly. He’s a friendly biologist about to submit his research to a prestigious journal!

Dr. Skelly has been drugged and locked up by none other than his rival, Dr. Pollution!

​

You, his lab assistants, must help him escape! To distract you from going straight to the police, Dr. Pollution has hidden the code to unlock Dr. Skelly’s restraints on a website. Part of the website has been given to you (how nice of Dr. Pollution). It’s up to you to find the remainder of the website.

https://tinyurl.com/_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Save Dr. Skelly Instructions

1. Working in a group of 1-3 (you may choose your groups), grab one envelope per group. You may write on the papers in the envelope, but please do not write on the envelope.

​

• Complete the tasks in your envelope to the best of your ability and without internet.

​

• After about ten minutes, Ms. Long will provide a wifi code and then you may use your devices.

Save Dr. Skelly Instructions

• Working in a group of 1-3 (you may choose your groups), grab one envelope per group. You may write on the papers in the envelope, but please do not write on the envelope.

​

• Complete the tasks in your envelope to the best of your ability and without internet.

​

• After about ten minutes, Ms. Long will provide a wifi code and then you may use your devices.

https://tinyurl.com/topsecretskellystuffbaadca

​

​

https://tinyurl.com/_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Part 1

Part 2

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Part 1 - Name the Lab Equipment

​

You have been given pictures of different pieces of lab equipment. Each picture has a number 1-12. Write out the name of each piece of lab equipment in the blanks with the corresponding number. If the equipment’s name has two words, omit the space. The final phrase makes up the first part of the website with Dr. Skelly’s information. The final phrase is made up of letters from the lab equipment.

​

The first one has been done for you.

​

B

E

A

K

E

R

K

R

1.

2.

​

3.

4.

5.

6.

The smaller piece (not the larger piece)

7.

8.

9.

10.

11.

12.

test tube

alcohol burner

funnel

hot plate

tongs

coverslip

thermometer

microscope

graduated cylinder

pipet

electronic scale

Part 2 - Multiple Choice Lab Safety Questions

​

Read through the multiple choice questions and choose the best answer. The letters of the correct answers will give the remaining 6 letters to the website.

1. After completing an experiment, all chemical wastes should be
1. left at your lab station for the next class.
2. disposed of according to your instructor’s directions.
3. dumped in the sink.
4. taken home.

​

• If a laboratory fire erupts, immediately
• notify your instructor.
• run for the fire extinguisher.
• throw water on the fire.
• open the windows.

​

• Horseplay or practical jokes in the laboratory are
• always against the rules.
• okay.
• not dangerous.
• okay if you are working alone.

​

​

4. You are heating a substance in a test tube. Always point the open end of the tube

• toward yourself.
• toward your lab partner.
• toward another classmate.
• away from all people.

​

5. When you finish working with chemicals, biological specimens, and other lab substances, always

1. treat your hands with skin lotion.
2. wipe your hands on a towel.
3. wash your hands thoroughly with soap and water.
4. wipe your hands on your clothes.

​

6. If an acid is splashed on your skin, wash at once with

1. plenty of water.
2. soap.
3. oil.
4. weak base.

​

___ ___ ___ ___ ___ ___

1 2 3 4 5 6

Measurements and Calculations

Measurements and Calculations

the comparison of an unknown quantity with a known fixed quantity

a mathematical determination of the amount or number of something

Module 1 - The Central Science

Measurements

Pages 11-26

• For centuries, units of measurement were not exact

• For centuries, units of measurement were not exact
• A person might

• For centuries, units of measurement were not exact
• A person might
• measure distance by counting steps

​

• For centuries, units of measurement were not exact
• A person might
• measure distance by counting steps
• measure time using an hourglass filled with sand

​

• For centuries, units of measurement were not exact
• A person might
• measure distance by counting steps
• measure time using an hourglass filled with sand
• measure using body parts

​

Covid Social Distancing Forms of Measurement

• But scientists need to report data that can be reproduced by other scientists, they need standard units of measurement

Units

SI units are a standardized system of units used by scientists all around the world

What SI Unit would you use to measure:

The length of a swimming pool?

What SI Unit would you use to measure:

The length of a swimming pool?

Meter (m)

What SI Unit would you use to measure:

The temperature of the water in the swimming pool?

What SI Unit would you use to measure:

The temperature of the water in the swimming pool?

What SI Unit would you use to measure:

The temperature of the water in the swimming pool?

Kelvin (K)

Units of Temperature

• Temperature is the measure of the average kinetic energy of particles that make up an object

​

• Scientists commonly use two equivalent units of temperature, the degree Celsius and the Kelvin

​

What SI Unit would you use to measure:

The volume of the swimming pool?

What SI Unit would you use to measure:

The volume of the swimming pool?

What SI Unit would you use to measure:

The volume of the swimming pool?

Cubic meters (m³)

What SI Unit would you use to measure:

The length of a pencil?

What SI Unit would you use to measure:

The length of a pencil?

Centimeter (cm)

What SI Unit would you use to measure:

The mass of an elephant?

What SI Unit would you use to measure:

The mass of an elephant?

Kilogram (kg)

What SI Unit would you use to measure:

The mass of an elephant?

Kilogram (kg)

What SI Unit would you use to measure:

The density of this piece of wood?

What SI Unit would you use to measure:

The density of this piece of wood?

What SI Unit would you use to measure:

The density of this piece of wood?

What SI Unit would you use to measure:

The density of this piece of wood?

Grams per cubic centimeter (g/cm³)

Units of Density

Density is the ratio of the mass of an object to its volume

​

Common units of density are grams per cubic centimeter (g/cm³) for solids and grams per milliliter (g/mL) for liquids and gases

What SI Unit would you use to measure:

The amount of energy produced by hydroelectric energy sources in the United States?

What SI Unit would you use to measure:

The amount of energy produced by hydroelectric energy sources in the United States?

Joules

Units of Energy

• The capacity to do work or produce heat is called energy
• The SI unit of energy is the joule (J)

Units

SI units are a standardized system of units used by scientists all around the world

​

A base unit is a defined unit in a system of measurement

​

Units

Prefixes added to SI base units indicate larger or smaller quantities

Derived Units

• Not all quantities can be measured with SI base units
• A unit that is defined by a combination of base units is called a derived unit

​

Derived Units

• Not all quantities can be measured with SI base units
• A unit that is defined by a combination of base units is called a derived unit

​

Derived Units

• Not all quantities can be measured with SI base units
• A unit that is defined by a combination of base units is called a derived unit

​

Derived Units

• Not all quantities can be measured with SI base units
• A unit that is defined by a combination of base units is called a derived unit

​

Numbers Without Units Mean NOTHING

For example:

• I bought 12.
• It weighs 90.
• The slurpee is 0.

​

Numbers Without Units Mean NOTHING

For example:

• I bought 12.
• It weighs 90.
• The slurpee is 0.

​

Instead:

• I bought 12 pencils.
• It weighs 90 kilograms.
• The slurpee is 0 degrees Celsius.

Numbers Without Units Mean NOTHING

​

Numbers without units will not receive full credit on assignments and tests.

Conversion Factors

• A conversion factor is a ratio of equivalent values having different units

One dozen eggs

12 eggs

Conversion Factors

A conversion factor is a ratio of equivalent values having different units

Dimensional Analysis

Dimensional Analysis is a systematic approach to problem solving that uses conversion factors to move, or convert from one unit to another

​

When using dimensional analysis, a conversion factor must cancel one unit and introduce a new one

Dimensional Analysis Practice

1. How many minutes are in two hours?

​

Dimensional Analysis Practice

1. How many minutes are in two hours?
• Starting point: 2 hours
• Conversion factor:
• 1 hour = 60 minutes

Dimensional Analysis Practice

1. How many minutes are in two hours?
• Starting point: 2 hours
• Conversion factor:
• 1 hour = 60 minutes

Dimensional Analysis Practice

1. How many minutes are in two hours?
• Starting point: 2 hours
• Conversion factor:
• 1 hour = 60 minutes

Dimensional Analysis Practice

1. How many minutes are in two hours?
• Starting point: 2 hours
• Conversion factor:
• 1 hour = 60 minutes

Dimensional Analysis Practice

1. How many minutes are in two hours?
• Starting point: 2 hours
• Conversion factor:
• 1 hour = 60 minutes

But why do we need to show our work like this?!

Grams and Molecules Practice

2. How many molecules of Br₂ react with 1.11 x 10²⁰ molecules of F₂?

Br₂ + 5F₂ → 2BrF₅

​

1. Identify the limiting reactant and the theoretical yield of phosphorous acid, H₃PO₃, if 225 g of PCl₃ is mixed with 123 g of H₂O.

PCl₃ + 3H₂O → H₃PO₃ + 3HCl

​

​

Dimensional Analysis Practice

2. How many miles will a person run during a 10.0 kilometer race?

• Starting point: 10.0 kilometers
• Conversion factors:
• 1.00 kilometers = 0.621 miles

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Dimensional Analysis Practice

2. How many miles will a person run during a 10.0 kilometer race?

• Starting point: 10.0 kilometers
• Conversion factors:
• 1.00 kilometers = 0.621 miles

​

Dimensional Analysis Practice

2. How many miles will a person run during a 10.0 kilometer race?

• Starting point: 10.0 kilometers
• Conversion factors:
• 1.00 kilometers = 0.621 miles

​

Dimensional Analysis Practice

2. How many miles will a person run during a 10.0 kilometer race?

• Starting point: 10.0 kilometers
• Conversion factors:
• 1.00 kilometers = 0.621 miles

​

Dimensional Analysis Practice

2. How many miles will a person run during a 10.0 kilometer race?

• Starting point: 10.0 kilometers
• Conversion factors:
• 1.00 kilometers = 0.621 miles

​

Dimensional Analysis Practice

3. How many seconds are in a day?

​

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

3. How many seconds are in a day?

• Starting point: 1 day
• Conversion factors:
• 1 day = 24 hours
• 1 hour = 60 minutes
• 1 minute = 60 seconds

​

Dimensional Analysis Practice

4. As an instructor is preparing for an experiment, he requires 225 g phosphoric acid. The only container readily available is a 150-mL Erlenmeyer flask. Is it large enough to contain the acid, the density of which is 1.83 g/mL?

4. As an instructor is preparing for an experiment, he requires 225 g phosphoric acid. The only container readily available is a 150-mL Erlenmeyer flask. Is it large enough to contain the acid, the density of which is 1.83 g/mL?

225 g

225 g of phosphoric acid (not including the beaker)

____?____ mL of phosphoric acid

Every 1.83 g of phosphoric acid is 1 mL

Dimensional Analysis Practice

4. As an instructor is preparing for an experiment, he requires 225 g phosphoric acid. The only container readily available is a 150-mL Erlenmeyer flask. Is it large enough to contain the acid, the density of which is 1.83 g/mL?

​

Yes, because the acid's volume will be 122.95 mL

Dimensional Analysis Practice

5. A student averaged 45 miles per hour on a trip. What was the student’s speed in feet per second?

​

5280 feet = 1 mile

Dimensional Analysis Practice

5. A student averaged 45 miles per hour on a trip. What was the student’s speed in feet per second?

​

5280 feet = 1 mile

​

66 feet per second

Extra Practice

A student needs 15.0 g of ethanol for an experiment. If the density of ethanol is 0.789 g/mL, how many milliliters of ethanol are needed?

​

​

​

Extra Practice

A student needs 15.0 g of ethanol for an experiment. If the density of ethanol is 0.789 g/mL, how many milliliters of ethanol are needed?

​

​

​

15.0 g

15.0 g of ethanol (not including the glass bottle)

____?____ mL of ethanol

Extra Practice

A student needs 15.0 g of ethanol for an experiment. If the density of ethanol is 0.789 g/mL, how many milliliters of ethanol are needed?

​

​

​

15.0 g

15.0 g of ethanol (not including the glass bottle)

____?____ mL of ethanol

Every 0.789 g of ethanol is 1 mL

Extra Practice

A student needs 15.0 g of ethanol for an experiment. If the density of ethanol is 0.789 g/mL, how many milliliters of ethanol are needed?

​

​

19.0 mL

Tuesday, September 9

1. Dimensional Analysis Review Questions
2. Measurements and Uncertainty in Data Notes
3. If time - go over Friday’s lab and the Measurements Google Form Quiz

Homework:

Uncertainty in Data Google Form Quiz - due Sunday, 9/14 at 11:59 PM

Module 1 and 2 Test on Wednesday, 9/24

Have your calculator, a writing utensil, and your chemistry binder

Extra Practice

A woman has a mass of 115 lb. What is her mass in grams?

​

​

​

​

Extra Practice

A woman has a mass of 115 lb. What is her mass in grams?

​

​

​

52162.85 grams

​

Review

• 7 Questions - 1 point per question
• Work with your partner
• Show your work (using dimensional analysis with units when applicable) and write your answers with units on the white board
• You cannot change your answers when Ms. Long says “Boards Up”

#1

#1

#2

What is the mass in grams of 1.00 gal of water? The density of water is 1.00 g/mL.

​

​

​

#2

What is the mass in grams of 1.00 gal of water? The density of water is 1.00 g/mL.

​

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3785.4 g

#3

#3

#4

#4

Extra Practice

Extra Practice

#5

#5

#6

#6

Challenge Question

A doctor is prescribing Drug X to a 72.7 kg patient. The doctor orders 5 milligrams per pound of patient weight of Drug X to be given per dosage. The supply of the drug is a solution, meaning the drug has been dissolved in water (not in pill or tablet form). The density of the solution is 0.9 g/mL. In other words, 1 mL of the solution contains 0.9 g of Drug X.

​

How many mL of solution need to be given to the patient per dose?

​

Conversion Factors:

​

1 kg = 2.2 pounds

1 pound = 0.45 kg

Challenge Question

A doctor is prescribing Drug X to a 72.7 kg patient. The doctor orders 5 milligrams per pound of patient weight of Drug X to be given per dosage. The supply of the drug is a solution, meaning the drug has been dissolved in water (not in pill or tablet form). The density of the solution is 0.9 g/mL. In other words, 1 mL of the solution contains 0.9 g of Drug X.

​

How many mL of solution need to be given to the patient per dose?

​

Conversion Factors:

​

1 kg = 2.2 pounds

1 pound = 0.45 kg

0.889 mL per dose

A doctor is prescribing Drug X to a 72.7 kg patient.

Drug X

72.7 kg patient

The doctor orders 5 milligrams per pound of patient weight of Drug X to be given per dosage.

Drug X

72.7 kg patient

The supply of the drug is a solution, meaning the drug has been dissolved in water (not in pill or tablet form). The density of the solution is 0.9 g/mL. In other words, 1 mL of the solution contains 0.9 g of Drug X.

​

Drug X in solution form with density of 0.9 g/mL

72.7 kg patient

How many mL of solution need to be given to the patient per dose?

​

Drug X in solution form with density of 0.9 g/mL

72.7 kg patient

A doctor is prescribing Drug X to a 72.7 kg patient. The doctor orders 5 milligrams per pound of patient weight of Drug X to be given per dosage. The supply of the drug is a solution, meaning the drug has been dissolved in water (not in pill or tablet form). The density of the solution is 0.9 g/mL. In other words, 1 mL of the solution contains 0.9 g of Drug X.

​

How many mL of solution need to be given to the patient per dose?

​

Conversion Factors:

​

1 kg = 2.2 pounds

1 pound = 0.45 kg

Measurements and Uncertainty in Data

In science, we spend a lot of time dealing with huge numbers…

Distance from earth to closest star outside our solar system

​

39,900,000,000,000 kilometers

https://www.bbc.com/news/science-environment-37167390

…and tiny numbers

The mass of an electron

​

0.000000000000000000000000000000910938356 kilograms

​

Another Example:

The Hope Diamond is the world’s largest deep-blue diamond. This diamond contains 460,000,000,000,000,000,000,000 atoms of carbon.

The Hope Diamond is the world’s largest deep-blue diamond. This diamond contains 460,000,000,000,000,000,000,000 atoms of carbon.

Carbon

460,000,000,000,000,000,000,000 of me!!!

The Hope Diamond is the world’s largest deep-blue diamond. This diamond contains 460,000,000,000,000,000,000,000 atoms of carbon. Each of these carbon atoms has a mass of 0.00000000000000000000002 g.

Carbon

Mass = 0.00000000000000000000002 g

460,000,000,000,000,000,000,000 of me!!!

The Hope Diamond is the world’s largest deep-blue diamond. This diamond contains 460,000,000,000,000,000,000,000 atoms of carbon. Each of these carbon atoms has a mass of 0.00000000000000000000002 g.

​

​

​

​

If you were to use these numbers to calculate the mass of the Hope Diamond, you would find that the zeros get in your way.

Scientific notation is a shorthand way to write numbers that are really big and really small.

​

​

Carbon atoms in the Hope Diamond = 4.6 x 10²³ carbon atoms

​

Mass of one carbon atom = 2 x 10^-23 grams

Scientific Notation

• In scientific notation, a given number is written as the product of two numbers: a coefficient and 10 raised to a power
• In scientific notation, the coefficient is always a number greater than or equal to one and less than ten

Scientific Notation Practice

Scientific Notation Practice

Scientific Notation

• In scientific notation, numbers are written in the form M x 10ⁿ, where the factor M is a number greater than or equal to 1 but less than 10, and n does not have a decimal
• Example -
• 65000 km = 6.5 x 10⁴ km
• 6.5 is the coefficient and 4 is the exponent

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​

​

Scientific Notation Practice

Scientific Notation

• When numbers are written in scientific notation, only the significant figures are shown

​

Scientific Notation Practice

Scientific Notation

• Determine M by moving the decimal point in the original number to the left or the right so that only one nonzero digit remains to the left of the decimal point.
• Determine n by counting the number of places that you moved the decimal point. If you moved it to the left, n is positive. If you moved it to the right, n is negative.

Example -

0.00012 mm = 1.2 x 10^-4 mm

​

Mathematical Operations Using Scientific Notation

• Addition and Subtraction
• Exponents must be the same
• Rewrite values to make exponents the same

Example #1 -

• 4.2 x 10⁴ kg + 7.9 x 10³ kg
• You must rewrite one of these numbers so their exponents are the same
• 4.2 x 10⁴ kg + __________________ = __________________

Mathematical Operations Using Scientific Notation

• Addition and Subtraction
• Exponents must be the same
• Rewrite values to make exponents the same

Example #1 -

• 4.2 x 10⁴ kg + 7.9 x 10³ kg
• You must rewrite one of these numbers so their exponents are the same
• 4.2 x 10⁴ kg + 0.79 x 10⁴ kg = 4.99 x 10⁴ kg

• Addition and Subtraction
• Exponents must be the same
• Rewrite values to make exponents the same

Example #2 - Determine the total amounts of energy produced by renewable energy sources in the United States

​

​

​

​

Total:

​

​

• Addition and Subtraction
• Exponents must be the same
• Rewrite values to make exponents the same

Example #2 - Determine the total amounts of energy produced by renewable energy sources in the United States

​

​

​

​

Total:

​

• Addition and Subtraction
• Exponents must be the same
• Rewrite values to make exponents the same

Example #2 - Determine the total amounts of energy produced by renewable energy sources in the United States

​

​

​

​

Total: 7.696 x 10¹⁸ J

​

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Wednesday, September 10

• Continue Measurements and Uncertainty in Data Notes
• Go over Friday’s lab and the Measurements Google Form Quiz
• Calculations and Significant Figures Wayground - unlimited attempts (upload a screenshot of your highest score to GC) - due next Friday, end of class

Homework:

Uncertainty in Data Google Form Quiz - due Sunday, 9/14 at 11:59 PM

Module 1 and 2 Test on Wednesday, 9/24

Have your calculator, a writing utensil, chemistry binder, and computer

Mathematical Operations Using Scientific Notation

• Multiplication
• Multiply coefficients.
• Add exponents.

Example -

(5.23 x 10⁶ mm) x (7.1 x 10^-2 mm) = ?

Mathematical Operations Using Scientific Notation

• Multiplication
• Multiply coefficients.
• Add exponents.

Example -

(5.23 x 10⁶ mm) x (7.1 x 10^-2 mm) = ?

(5.23 x 7.1) x (10⁶ mm x 10^-2 mm)

= 37.133 x 10⁴ mm² = 3.7 x 10⁵ mm²

Mathematical Operations Using Scientific Notation

• Division
• Divide coefficients.
• The exponent of the denominator is subtracted from that of the numerator.

Example -

​

​

Mathematical Operations Using Scientific Notation

• Division
• Divide coefficients.
• The exponent of the denominator is subtracted from that of the numerator.

Example -

​

= 0.6716049383 x 10³ g/mL = 6.7 x 10² g/mL

Practice Questions: Solve the following problems.

1. (7 x 10⁸) - (4 x 10⁸)

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• (4 x 10²) x (1 x 10⁸)

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​

• (8 x 10⁴) / (4 x 10¹)

​

​

• (4.39 x 10⁵ kg) - (2.8 x 10⁷ g) in kg

​

Guess the Age

Guess the Age

Guess how old Alfonso Ribeiro is

Guess the Age

Guess how old Alfonso Ribeiro is

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​

​

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53 years old

Guess the Age

Guess how old Alfonso Ribeiro is

​

​

53 years old

​

Guesses close to 53 years old are more accurate than those that are farther

Accuracy and Precision

Accuracy refers to how close a measured value is to an accepted value

​

Precision refers to how close a series of measurements are to one another

You were given a solution with an unknown volume. Which piece of lab equipment should you use to find the volume: 100 mL beaker or 100 mL graduated cylinder?

You were given a solution with an unknown volume. Which piece of lab equipment should you use to find the volume: 100 mL beaker or 100 mL graduated cylinder?

You were given a solution with an unknown volume. Which piece of lab equipment should you use to find the volume: 100 mL beaker or 100 mL graduated cylinder?

A graduated cylinder is regularly used for measuring volume and is considered more accurate than a beaker because the graduated cylinder has permanently-marked increments (more lines of measurement)

Error

• Error - the difference between an experimental value and an accepted value

​

• Percentage Error - calculated by subtracting the accepted value from the experimental value, dividing the absolute value of the difference by the accepted value, and then multiplying by 100

%

%

Percentage Error Practice

1. A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement? Show your work with units.

​

Percentage Error Practice

1. A student measures the mass and volume or a substance and calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percentage error of the student’s measurement? Show your work with units.

​

7.69%

What are some examples of sources of error in #1?

What are some examples of sources of error in #1?

Water and a variety of solvents can expand or contract, depending on the temperature

What are some examples of sources of error in #1?

Contaminated glassware or a contaminant in a substance would no longer make the substance pure

What are some examples of sources of error in #1?

Limitations of measuring instruments

Percentage Error Practice

• A volume is measured experimentally as 4.26 mL. What is the percentage error, given that the correct value is 4.15 mL? Show your work with units.

Percentage Error Practice

• A volume is measured experimentally as 4.26 mL. What is the percentage error, given that the correct value is 4.15 mL? Show your work with units.

2.65%

Error in Measurement

• Some error or uncertainty always exists in any measurement
• Often, precision is limited by the measuring instruments

What is the length of the object pictured on the right?

Error in Measurement

• Some error or uncertainty always exists in any measurement
• Often, precision is limited by the measuring instruments

Significant Figures

• Significant figures - all the digits measured precisely, plus one estimated digit
• In the example below, the measurement is 5.23 cm. The last digit, 3, is uncertain. All digits, including the uncertain one, are significant.

Significant Figures

You have a graduated cylinder that contains a liquid. Write the volume of the liquid, in millimeters, using the proper number of significant figures.

​

​

​

Significant Figures

You have a graduated cylinder that contains a liquid. Write the volume of the liquid, in millimeters, using the proper number of significant figures.

​

​

The volume in the cylinder is 19.5 mL.

​

​

​

Significant Figures

You have a graduated cylinder that contains a liquid. Write the volume of the liquid, in millimeters, using the proper number of significant figures.

​

​

The volume in the cylinder is 19.5 mL.

​

​

​

Estimated digit

Known digit

Known digit

Significant Figures

You have a graduated cylinder that contains a liquid. Write the volume of the liquid, in millimeters, using the proper number of significant figures.

​

​

The volume in the cylinder is 19.5 mL.

​

​

​

Volumes in the graduated cylinder can be read with certainty to 1 mL, and with some uncertainty to 0.1 mL, so this measurement has 3 significant figures

Significant Figures

You place an object on a scale and read the mass in grams according to the picture. How many significant figures are in this measurement?

​

​

​

Significant Figures

You place an object on a scale and read the mass in grams according to the picture. How many significant figures are in this measurement?

​

​

The mass 21.427 g has five significant figures

Significant Figures

1. Nonzero numbers are always significant.
1. Examples:
• 38.2 L has three significant figures
• 87921 m has five significant figures

Rules for Significant Figures

2. All final zeros to the right of the decimal place are significant.

• Examples:
• 6.20 g has _____ significant figures
• 518.0 L has _____ significant figures

Rules for Significant Figures

2. All final zeros to the right of the decimal place are significant.

• Examples:
• 6.20 g has three significant figures
• 518.0 L has four significant figures

Rules for Significant Figures

3. Any zero between significant figures is significant.

• Example:
• 60.5 g has ____ significant figures.
• 4034 mL has ____ significant figures.

​

Rules for Significant Figures

3. Any zero between significant figures is significant.

• Example:
• 60.5 g has three significant figures.
• 4034 mL has four significant figures.

​

Rules for Significant Figures

4. Placeholder zeros are not significant. To remove placeholder zeros, rewrite the number in scientific notation.

• Examples:
• 0.0253 g has ____ significant figures.
• 4320 g has ____ significant figures.

Rules for Significant Figures

4. Placeholder zeros are not significant. To remove placeholder zeros, rewrite the number in scientific notation.

• Examples:
• 0.0253 g has three significant figures.
• 4320 g has three significant figures.

Rules for Significant Figures

5. Counting numbers and defined constants have an infinite number of significant figures.

• Examples:
• 6 molecules
• 60 seconds = 1 minute

Significant Figures Practice

• How many significant figures are in each of the following measurements?
1. 28.6 g
2. 3440.0 cm
3. 910 m
4. 0.04604 L
5. 0.0067000 kg

Friday, September 12

• Calculations and Significant Figures Wayground (code: 714375) - unlimited attempts (upload a screenshot of your highest score to GC) - due next Friday, end of class
• Density Lab - due next Friday

Homework:

Uncertainty in Data Google Form Quiz - due Sunday, 9/14 at 11:59 PM

Density Lab - due next Friday 9/19 start of class (hand in)

Module 1 and 2 Test on Wednesday, 9/24

Have your calculator, a writing utensil, chemistry binder, and computer

Significant Figures and

Rounding Numbers

What is the point of significant figures?

What is the point of significant figures?

• Significant figures tell us how to round

What is the point of significant figures?

• Significant figures tell us how to round
• But more importantly, the point of significant figures is to make sure that the answer you get isn’t more precise than the numbers your started with

Most of the math that we do in science is with numbers that are measurements

​

Some measurements are precise, and some are not so precise

For example:

rock

You want to know the mass of this rock.

rock

​

​

Scale #1:

$10 USD

​

rock

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Scale #1:

​

82 g

​

​

Scale #1:

​

82 g

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​

Scale #1:

​

​

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Lab Equipment #2:

​

$2000 USD

​

82 g

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Scale #1:

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​

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Lab Equipment #2:

82 g

82.1039 g

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​

Scale #1:

​

​

​

Lab Equipment #2:

82 g

82.1039 g

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Scale #1:

​

Now you want to calculate the density of the rock.

​

​

Scale #2:

82 g

82.1039 g

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​

Scale #1:

​

You use the mass from Scale #1 to help you find the rock’s density.

82 g

​

​

Scale #1:

​

82 g

You used a beaker to find the volume of the rock and measured 42 mL

​

​

Scale #1:

​

Now you want to calculate the density of the rock.

82 g / 42 mL =

​

​

Scale #1:

​

Now you want to calculate the density of the rock.

82 g / 42 mL = 1.952380952 g/mL

​

​

Scale #1:

​

Now you want to calculate the density of the rock.

82 g / 42 mL = 1.952380952 g/mL

This value looks so precise - like it only could have been measured with super expensive, precise equipment

​

​

Scale #1:

​

Now you want to calculate the density of the rock.

82 g / 42 mL = 1.952380952 g/mL

So instead, the answer should not be more precise than what we started with

​

​

Scale #1:

​

Now you want to calculate the density of the rock.

82 g / 42 mL = 2.0 g/mL

Now the answer is just as precise as what we started with

​

​

Scale #2:

​

82.1039 g / 42.9338572 mL = 1.91233511 g/mL

On the other hand, if we measured with super sensitive equipment, it would make sense to get an answer that is very precise

82.1039 g

Practice Questions

Complete the practice questions individually. We will go over the first page together. The answers to the second page are posted on Google Classroom for you to check your work.

Rounding Numbers

• Calculators are not aware of significant figures.
• Answers should not have more significant figures than the original data with the fewest figures, and should be rounded.

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Rounding Numbers Example

• Suppose you used a calculator to divide a measured value of 154 g by a measured value of 327 mL. Each of these values has three significant figures so the answer needs to be rounded off to make its degree of certainty match that in the original measurements. The answer should be 0.471 g/mL.

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Rules for Rounding Numbers

1. If the digits to the right of the last significant figure is greater than 5, round up the last significant figure.
• Example (rounded to three significant figures) -
• 42.68 g → 42.7 g

Rules for Rounding Numbers

2. If the digit to the right of the last significant figure is less than 5, do not change the last significant figure

• Example (rounded to three significant figures)
• 17.32 m → 17.3 m

Rules for Rounding Numbers

3. If the digits to the right of the last significant figure are a 5 followed by a nonzero digit or no other number at all, round up the last significant figure

• Example (rounded to three significant figures)
• 2.7851 cm → 2.79 cm

Rounding Numbers (cont.)

• Multiplication and Division
• Round the answer to the same number of significant figures as the original measurement with the fewest significant figures.

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Example -

Rounding Numbers (cont.)

• Multiplication and Division
• Round the answer to the same number of significant figures as the original measurement with the fewest significant figures.

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Example -

Rounding Numbers (cont.)

• Addition and Subtraction
• Round the answer to the same number of decimal places as the original measurement with the fewest decimal places.

Example -

Rounding Numbers (cont.)

• Addition and Subtraction
• Round the answer to the same number of decimal places as the original measurement with the fewest decimal places.

Example -

Significant Figures Practice

• Carry out the following calculations. Express each answer to the correct number of significant figures.
1. 5.44 m - 2.6103 m

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• 2.4 g/mL x 15.82 mL

Significant Figures Practice

• Carry out the following calculations. Express each answer to the correct number of significant figures.
• 5.44 m - 2.6103 m
• 2.83 m
• 2.4 g/mL x 15.82 mL
• 38 g

451 cm

101 cm

Br₂ is a(n) ________________

Thursday, September 21

Work Day

• Study Guide - on Google Classroom
• Review Packet - optional
• If you did not submit the Properties of Matter Google Form, do this now

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Homework:

• Procedure Write-Up due Saturday, 8:05 AM
• Pre-Demo and Post-Demo Questions due Saturday, 8:05 AM

Module 1-2 Test on Monday, September 25

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Friday, September 22

1. Separating a Mixture Lab - due Wednesday, 3:05 PM - upload pic to GC

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Homework:

• Procedure Write-Up due Saturday, 11:05 AM
• Pre-Demo and Post-Demo Questions due Saturday, 11:05 AM
• Optional:
• Study Guide - on Google Classroom
• Review Packet

Module 1-2 Test on Monday, September 25

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Friday, September 22

1. Separating a Mixture Lab - due Wednesday, 1:15 PM - upload pic to GC

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Lab Safety

Saturday, September 23

1. Review Jeopardy
2. Self Study

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Homework:

• Study for the Test on Monday
• Optional:
• Study Guide - on Google Classroom
• Review Packet

Module 1-2 Test on Monday, September 25

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Wednesday, November 1

Jeopardy Review

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Tomorrow: more review

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Midterm on Monday

Jeopardy Instructions

• Get into a group of 2-3 and sit with your teammates
• Grab one white board
• Have a calculator, a periodic table, and your notes

#6

Which of the following must remain constant in the following closed system - a sealed bottle of soda taken out of the refrigerator

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1. Energy
2. Mass
3. Temperature
4. Speed