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Chemistry

August 20

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Instructions- chemistry

Turn in homework.
Read the article on flammable items.
In your data on “Mystery of the Burned Towel”, write down which of the flammable items in the article might likely be responsible for the burned towel.

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Section 3, Question 16

16. Give an example of quantitative and qualitative data.

Answer:

Qualitative: silver colored liquid

Quantitative: 5 mL

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Section 3, Question 17

17. You are asked to study the effect of temperature on the volume of a balloon. The balloon’s size increases as it is warmed. What is the independent variable? The dependent variable? What factor is held constant? How would you construct a control?

Answer:

Independent variable: temperature

Dependent variable: size of balloon

Constant/Controlled: amount of air in balloon

Control: identical balloon at room temperature

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Section 4, Question 23

23. Summarize the reason behind the following.

Wear goggles and an apron in the lab even if you are only an observer
Do not return unused chemicals to the stock bottle.
Do not wear contact lenses in the lab.
Avoid wearing loose, draping clothing and dangling jewelry.

Answer:

Harmful substances can get in your eyes and on your clothing if you are performing an experiment or just watching it being performed.
The chemicals might be contaminated, and you do not want to contaminate the stock bottle.
Contact lenses can absorb gases that can damage your eyes, and they are difficult to remove during an emergency.
It is easy to drag these items through chemicals and cross flames, which might create a hazardous situation.

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Chapter 2 Section 1 Notes

Analyzing Data: Units and Measurements

Quantity	Base Unit	Based on what?
Time	Second (s)	Frequency of radiation given off by a cesium-133 atom
Length	Meter (m)	Distance that light travels in a vacuum in 1/299,792,458 of a second
Mass	Kilogram (kg)	A platinum and iridium cylinder kept in France stored in a vacuum under a triple bell jar
Temperature	Kelvin (K)
Amount of Substance	Mole (mol)
Electric Current	Ampere (amp)
Luminous Intensity	Candela (cd)

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A Note about temperature

Fahrenheit scale: water freezes at 32 degrees and boils at 212 degrees

Celsius scale: Freezing point 0 degrees, boiling point 100 degrees

Zero Kelvin is where are all particles are in lowest possible energy state, water freezes at 272.15 K and boils at 373.15 K

K = C + 273

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Converting among units

Prefix	Symbol	Numerical Value in Base Units	Power of 10 Equivalent
Giga	G	1,000,000,0001	10^9
Mega	M	1,000,000	10^6
Kilo	k	1000	10^3
-	-	1	10^0
Deci	d	0.1	10^-1
Centi	c	0.01	10^-2
Milli	m	0.001	10^-3
Micro		0.000001	10^-6
Nano	n	0.000000001	10^-9
Pico	p	0.000000000001	10^-12

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Section 1, Question 5

5. Describe how adding the prefix mega- to a unit affects the quantity being described.

Answer: It multiples the quantity by 10^6.

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Derived units

a unit that is defined by a combination of base units

Quantity	Derived Unit
Volume- space occupied by an object	m^3 or L
Density- physical property of matter that is amount of mass per unit volume	g/cm^3 Density = mass/volume

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Section 1, Question 2

2. What is the volume of a sample that has a mass of 20 g and a density of 4 g/mL?

Answer: Volume = 5 mL

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Section 1, Question 9

9. Samples A, B, and C have masses of 80 g, 12 g, and 33 g, and volumes of 20 mL, 4 cm^3, and 11 mL, respectively. Which of the samples have the same density?

Answer:

Density of A = 80 g/20 mL = 4 g/mL

Density of B = 12 g/4 cm^3 = 3 g/cm^3

Density of C = 33 g/11 mL = 3 g/mL

B and C have the same density

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Scientific notation

Number	Scientific Notation
460,000,000,000,000,000,000,000	4.6 x 10^23
0.00000000000000000002	2 x 10^-23

https://learn.genetics.utah.edu/content/cells/scale/

Scientific Notation- can be used to express any number as a number between 1 and 10 (known as the coefficient) multiplied by 10 raised to a power (known as the exponent)

*A note about calculations*

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Section 2, Question 25

25. Express the numbers 0.00087 and 54,200,000 in scientific notation.

Answer: 8.7 x 10^-4, 5.42 x 10^7

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Section 2, Question 26

26. Write the measured distance quantities 3 x 10^-4 cm and 3 x 10^4 km.

Answer: 0.0003 cm, 30,000 km

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Burned Towel questions from last week- any more?

Which products do you use? Foundation, mascara, fingernail polish, shampoo, conditioner, hairspray, face wash, body wash, lip gloss

What color was the fire? Orangy yellow- seemed like a typical fire

What kind of chemicals are in the products?- I have no idea

Is your house water supply chlorinated?- yes

Did you use something with a cord?- I did blow dry my hair

How much water did it take to put the fire out?- a few

Is Whiskers able to get onto the counter?- yes

What kind of cat is Whiskers?- siamese

Where was the cat when she left?- on the counter

What was the towel used for?- wiping my face

Does your cat want revenge?? Or use hairspray…- my cat loves me!

Were the products on the towel?

Did you use hair spray?

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Station 1- density

At this station, we will be calculating the density of the bathroom tile. Use the scale to measure the mass and the graduated cylinder to measure the volume. To measure the volume fill the graduated cylinder with water to a certain point. Then measure how much the water rises when you put the tile in. This is the volume! Use the mass and volume to calculate density.

*Note, when measuring volume in a graduated cylinder, look from the side and notice the dip in the water. Measure at the bottom of the dip. This is called the “meniscus”.

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Station 2- area

Take a look at the burned towel. Write down some qualitative data about the towel. Then use the ruler to measure the approximate length and width of the affected area on the towel. Use those measurements to calculate the area.

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Station 3- design an experiment

In order to find out what happened to the towel, it is important to be able to understand what conditions could cause a towel to burn. If I supplied you with these materials: a towel, a lighter, hydrogen peroxide, rubbing alcohol, and fingernail polish remover, how would you set up an experiment to test this? Include these components: Question, Hypothesis, Independent Variable, Dependent Variable, and Controls. Remember, the independent variable is the one that YOU change in the experiment, and the dependent variable is the one that you are measuring as a result of that change. Controls are kept the same. You can also have a control that you compare the others to. To construct your hypothesis use this model IF….THEN… In other words, if I change this one factor, then this will happen to the other.

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Station 4-panel of liquids

Before you are 4 different liquids. Could any of them be responsible for the fire? It’s difficult to tell what they are just by looking, though. Take some data to see if we can get a better picture of what they might be.

When measuring mass, volume, and density, pour 10 mL of each liquid into a cup. Measure the mass on the scale by measuring an empty cup, then the amount in the cup, and subtract. Then use the formula

density = mass/volume

to calculate the density. Remember to “waft” when smelling!