Chemistry

Mr. Lansing

Chapter 2 -Matter and Change

• 2.1 Properties of Matter
• 2.2 Mixtures
• 2.3 Elements and Compounds
• 2.4 Chemical Reactions

2.1 Properties of Matter

Key Questions:

• Why do all samples of a substance have the same intensive properties
• What are three states of matter?
• How can physical changes be classified?

Vocabulary

- mass - substance - gas

- volume - physical property - vapor

- solid - extensive property - liquid

- physical change

- intensive property

2.1 Properties of Matter

Extensive Properties

• mass- the amount of matter the object contains
• volume- the space occupied by an object
• extensive property- a property that depends on the amount of matter in a sample (length, weight)

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Intensive Properties

• intensive property- a property that depends on the type of matter, NOT the amount of matter

- Example: The hardness or material of a ball

- Color, odor, luster, malleability, melting point,

freezing point, boiling point, density

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"Does i matter how much of the sample I have?"

If yes, then extensive. If no, then intensive

2.1 Properties of Matter

Identifying a Substance

• Each object has a different chemical makeup, or composition
• Substance - matter that has a uniform and definite composition. (examples: aluminum and copper)
• Every sample of a given substance has identical intensive properties because every sample has the same composition
• Physical property - a quality or condition of a substance that can be observed or measured without changing the substance's composition
• Ex: Hardness, color, conductivity, and malleability are all physical properties.

2.1 Properties of Matter

States of Matter

• What is matter?
• Anything that has mass and takes up space
• The three states of matter are solid, liquid and gas
• Solid- a form of matter with definite shape and volume
• Liquid- a form of matter that has an indefinite shape, with a fixed volume
• Gas- a form of matter that takes the shape and volume of its container (gas @ room temperature)
• Vapor- the gaseous state of a substance that is generally a liquid or solid at room temperature

(Ex. water vapor)

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2.1 Properties of Matter

Physical Changes

• Physical change- some properties of a material change, but the composition of the material does NOT change
• Physical changes can be classified as reversible (changing from one state to another) or irreversible (cutting hair, cracking an egg).
• Ex. Tearing up paper, mixing salt and water

2.2 Mixtures

Key Questions:

• How can mixtures be classified?
• How can mixtures be separated?

Vocabulary

- mixture - phase

- heterogenous mixture - filtration

- homogenous mixture - distillation

- solution

2.2 Mixtures

Classifying Mixtures

• Mixture- a physical blend of two or more components
• Heterogeneous mixture- a mixture in which the composition is NOT uniform throughout
• Homogenous mixture- a mixture in which the composition is uniform throughout (also known as a solution)
• Phase- describes any part of a sample with uniform composition and properties
• Homogenous mixtures consists of a single phase
• Heterogenous mixtures consists of two or more phases

2.2 Mixtures

Separating Mixtures

• Differences in physical properties can be used to separate mixtures
• Filtration - the process that separates a solid from the liquid in a heterogenous mixture (Ex. draining pasta or brewing coffee)
• Distillation - a liquid is boiled to produce vapor that is then condensed back into a liquid (used to remove impurities in water)

2.3 Elements and Compounds

Key Questions:

• How are elements and compounds different?
• How can substances and mixtures be distinguished?
• What do chemists use to represent elements and compounds?
• Why is a periodic table useful?

Vocabulary

- element - chemical symbol - group

- compound - periodic table - period

- chemical change

2.3 Elements and Compounds

Distinguishing Elements and Compounds

• Element - the simplest form of matter that has a unique set of properties
• Compound- a substance that contains two or more elements chemically combined in a fixed proportion
• Compounds can be broken down into simpler substances by chemical means, but elements CANNOT

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2.3 Elements and Compounds

Breaking Down Compounds

• Chemical change - a change that produces matter with a different composition than the original matter
• Example: Heating sugar causes it to go through a series of chemical changes
• The final products are solid carbon and water vapor

2.3 Elements and Compounds

Properties of Compounds

• Properties of compounds are quite different from those of their component elements.
• Ex: Sodium and Chlorine --> Sodium Chloride
• Sodium - soft gray metal, sodium vapor produces the light in street lamps
• Chlorine- pale yellow-green poisonous gas, used to kill harmful organisms in swimming pools
• Sodium Chloride - white solid, also known as table salt

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2.3 Elements and Compounds

Distinguishing Substances and Mixtures

• If the composition of a material is fixed = substance
• If the composition of a material may vary = mixture
• Classification of Matter Flow Chart

2.3 Elements and Compounds

Symbols and Formulas

• Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds.
• Each element is represented by a one or two letter chemical symbol
• Elements : Ca (calcium), C (carbon), Na (sodium)
• Compounds: H₂0 (water), CO₂ (carbon dioxide)

2.3 Elements and Compounds

Periodic Table

• An arrangement of elements in which the elements are separated into groups based on repeating properties
• Periodic Table - allows scientists to easily compare the properties of one element to another element.
• Period - the horizontal rows of the periodic table
• Group -the vertical columns of the periodic table, also known as families.
• elements within the same group/family have similar chemical and physical properties

2.4 Chemical Reactions

Key Questions:

• What always happens during a chemical change?
• What are four possible clues that a chemical change has taken place?
• How are the mass of the reactants and the mass of the products of a chemical reaction related?

Vocabulary

- chemical property - product

- chemical reaction - precipitate

- reactant

- law of conservation of mass

2.4 Chemical Reactions

Chemical Changes

• Chemical property - the ability of a substance to undergo a specific chemical change
• During a chemical change, the composition of matter ALWAYS changes
• Remember - during a physical change the composition NEVER changes
• A chemical change is also called a chemical reaction, one or more substances change into one or more new substances
• Reactant - a substance present at the start of a reaction
• Product - a substances produced in the reaction

2.4 Chemical Reactions

Recognizing Chemical Changes

• Four clues to determine if a chemical change has taken place
• a transfer of energy
• a change in color
• the production of gas
• the formation of a precipitate
• Precipitate - a solid that forms and settles out of a liquid mixture
• The only way to be sure that a chemical change has occurred is to test the composition of a sample before and after the change
• Ex. mixing vinegar and baking soda

2.4 Chemical Reactions

Conservation of Mass

• During any chemical reaction, the mass of the products is always equal to the mass of the reactants
• Law of Conservation of Mass- in any physical change or chemical reaction, mass is conserved (neither lost nor destroyed)

Chapter 2- Homework

• Pg 117 # 39, 44, 48, 50, 52, 53, 54, 55, 60, 62, 67, 73, 75, 77, 80

Chapter 2 Warm Up (10 points)

• What is the difference between intensive and extensive properties? List 4 examples of each

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• What is the difference between gas and vapor?

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• What is the difference between a physical and chemical change? List 4 examples of each

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4. Define element, compound, heterogeneous mixture and homogeneous mixture. Give 4 examples of each

Chapter 2 Warm Up (10 points)

1. Extensive- depends on the amount of matter

-mass, volume, length, weight

Intensive- depends on type of matter (not amount!)

- color, density, melting point, boiling point, odor

2. Vapor- at room temperature substance is solid/liquid

Gas- at room temperature substance is gas

3. physical change- properties of material change but the composition does not

- breaking glass, melting ice, tearing paper, cutting hair

chemical change- produces matter with different composition than original matter

- bleaching hair, rust, explosions, bubbles

Chapter 2 Warm Up (10 points)

4. Element- simplest form of matter

- gold, silver, copper, arsenic, sodium

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Compound- substance with two or more elements chemically combined in fixed proportions

- water (H₂O), salt (NaCl), sugar (C₆H₁₂O₆) ,

calcium oxide (CaO)

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Homogeneous mixture- uniform in composition, the same throughout (ex. saltwater, air, cooking oil)

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Heterogenous mixture- not uniform in composition, different layers (ex. paint, chocolate chip ice cream, granite)