Chapter 2 - Matter and Change

Chapter 2 – Matter & ChangeBy Kendon Smith – Columbia Central HS – Brooklyn, MI

I. Properties of Matter

1. Matter is defined as anything that has mass and volume.

a. Mass: the amount of matter an object contains.

b. Volume: the amount of space an object occupies.

Chapter 2 – Matter and Change

2. Describing Matter

a. Extensive Property: property that depends on the amount of matter in a sample

b. Intensive Property: property that depends on the type of matter in a sample

Examples: Identify the following properties of a sample as extensive or intensive.

Mass: ___ Color: ___ Flammability: ___

Volume: ___ Density: ___ Melting Point: ___

3. Identifying Substances

a. Substance: matter that has uniform and definite composition.

- Uniform means it is the same throughout the sample.

- Definite composition means chemically the same all over the planet!

Examples: Water? Sand? Copper? Salt?

b. Physical Property – a quality or condition of a substance that can be measured or observed without changing a substance’s composition.

Examples: color, solubility, odor, hardness, density,

melting point, boiling point, physical state, mass, volume

4. States of Matter

A. Solids – form of matter with definite shape and definite volume

- Particles are packed tightly together

B. Liquids – form of matter with indefinite shape and definite volume

- Liquids take the shape of their container - Particles in liquids are almost incompressible - Particles in liquids usually expand slightly

when heated. - Particles in a liquid are close together, but

can flow past each other

4. States of Matter

C. Gases – form of matter with indefinite shape and indefinite volume

- Particles in gases very far apart compared to liquids and solids.

- Particles in gases are easily compressed, pushing closer together.

* Vapors – Gaseous substances that are liquids or solids at room temperature.

States of Matter

5. Physical changes – alter a material without changing its chemical composition

- Physical changes can be classified as reversible or irreversible

a. Reversible changes: melt, freeze, boil, condense

b. Irreversible changes: break, split, grind,

cut, crush

II. Mixtures

1. Mixture – a physical blend of two or more

substances.

a. Homogeneous mixture:

- completely uniform composition,

- parts are not readily distinguished

Examples – brine, gatorade, jello, creamy peanut butter

II. Mixtures

1. Mixture – a physical blend of two or more

substances.

b. Heterogeneous mixture:

- not uniform composition

- parts are readily distinguished

Examples – sand and water, a salad, jello w/ fruit, chunky peanut butter

2. Solution – a homogeneous mixture - may be solid, liquid, or gas

Examples – brine, sugar water, air, stainless steel

3. Phase – any part of a sample that with uniform composition and properties

How many phases?

Brine = ___ Oil/Vinegar = ___ Air = ___ Sand/Water = ___

4. Separating Mixtures: Mixtures can be separated using physical means.

a. Decant, or pour off, a liquid layer.

Ex. Oil/Water Mix

b. Filtration: Separates solids from liquids with their

dissolved particles.

c. Distillation – Boil a liquid to become a vapor and condense it back.

d. Magnet – Pull out magnetic particles from a mixture.

e. Sorting - Physically separating by appearance

Ex. size, color, shape

III. Elements and Compounds

1. Distinguishing elements and compounds

a. Elements – the simplest form of matter with a unique set of properties

- Elements are the basic building blocks of all other substances.

- Cannot be separated into simpler substances by chemical means.

Examples: hydrogen, oxygen, carbon

III. Elements and Compounds

b. Compounds – two or more elements chemically combined in a fixed proportion

- Compounds can only be separated into simpler substances by chemical means,

but not by physical means, like mixtures.

Examples: water (H2O) sucrose (C12H22O11) carbon dioxide (CO2) sugar water???

III. Elements and Compounds

c. Chemical change: produces matter with a different composition

- Bonds are broken to chemically separate elements.

- New bonds are formed to chemically join elements.

Example 1: sucrose (table sugar)

C12H22O11

HEAT12 C + 11 H2O

III. Elements and Compounds

c. Chemical change: produces matter with a different composition

- Bonds are broken to chemically separate elements.

- New bonds are formed to chemically join elements.

Example 2: water (electrolysis)

2 H2OELECTRICITY

2 H2 + O2

III. Elements and Compounds

2. Properties of Compounds

a. Properties of compounds can be quite different from those of their component elements.

- Each compound is a new, pure substance

with unique properties.

a. Properties of compounds can be quite different from those of their component elements.

Example 1: Water – made of hydrogen and oxygen

Properties: Hydrogen:

Oxygen:

Water:

Extremely flammable gas

Gas that supports combustion

Non-flammable liquid!

a. Properties of compounds can be quite different from those of their component elements.

Example 2: Table Salt – made of sodium and chlorine

Properties: Sodium:

Chlorine:

Sodium chloride:

Soft, silvery metal that reacts violently with water

Poisonous, yellowish gas

white, crystalline solid that we must eat!

III. Elements and Compounds

3. Distinguishing Substances and Mixtures

a. Fixed composition – the material is a substance

b. Variable composition – the material is a mixture

KEY CONCEPT!

* Homogeneous mixtures look like substances because both appear to be made of one kind of matter.

Matter

Substance(definite

composition)

Mixture(variable

composition)

Can be

physically separated

Element Compound

Can be chemically separated

Homogeneous(uniform; called

a solution)

Heterogeneous(not uniform;

distinct phases)

Matter

Substance(definite

composition)

Mixture(variable

composition)

Element Compound Homogeneous(uniform; called

a solution)

Heterogeneous(not uniform;

distinct phases)

looks like

4. Symbols and Formulas

a. Chemical symbol – one or two letters which represent each element

- First letter of the symbol is always capitalized, while the second letter is always lower case.

- Most symbols are derived from the Latin names for the elements.

Name Latin Symbol

Sodium Natrium Na

Potassium Kalium K

Antimony Stibium Sb

Gold Aurum Au

Silver Argentum Ag

Iron Ferrum Fe

Lead Plumbum Pb

Mercury Hydrargyrum Hg

Tungsten Wolfran W

Copper Cuprum Cu

b. Chemical formulas – use symbols to show the relative proportions of elements in a compound.

- Because compounds have fixed compositions, the chemical formula

for a compound is always the same.

- Subscripts are written next to the symbol and give us the proportion

of each element in the compound.

i. The number one is never written as a subscript,

it is assumed!

ii. If a subscript is written outside parenthesis, it multiplies the proportions of all the elements inside the parenthesis.

Examples: What are the proportions of elements in each of the following compounds?

1. Table sugar (sucrose) = 12 carbons, 22 hydrogens, 11 oxygens

2. C2H5OH (ethanol) = 2 carbons, 6 hydrogens, 1 oxygen

3. Al(OH)3 = 1 aluminum, 3 oxygens, 3 hydrogens

4. (NH4)2CO3 = 2 nitrogens, 8 hydrogens, 1 carbon, 3 oxygens

5. Co3(PO4)2 = 3 cobalts, 2 phosphorus, 8 oxygen

IV. Chemical Reactions

1. Chemical Changes: always involve a change in chemical composition

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

b. Words that signify chemical change: burn, rot, rust, decompose, ferment, explode, corrode

c. Chemical properties can only be observed while a substance is undergoing a chemical change, during what is called a chemical reaction

IV. Chemical Reactions

2. Chemical reaction – one or more substances change into new substances

a. Reactant – a substance present at the start of the reaction (BEFORE!)

b. Product – a substance produced during a reaction (AFTER!)

REACTANTS PRODUCTS

3. Some basics rules for writing chemical reactions:

a. Reactants written on the left and products on the right with an arrow between.

b. Reactants are separated from each other with a + symbol. Same for products.

c. The arrows always points toward the products and can be read as “yields” or “produces” or “changes into”.

Example 1 - Oxidation of Iron: The reaction between iron and oxygen yields

iron oxide.

Iron + Oxygen Iron oxide

Example 2: During combustion, ethanol reacts

with oxygen and produces carbon dioxide and water.

ethanol + oxygen carbon dioxide + water

4. Recognizing Chemical Changes

a. Clues that a chemical reaction has taken place:

1. Energy is absorbed or released - hot or cold!

Examples: Burning wood – gives off heat Cook food – absorbs heat

*Note: There are energy changes during changes of state, which are only physical changes, so energy

change alone is not sufficient!

a. Clues that a chemical reaction has taken place:

2. Change in color = new chemical has been formed!

3. Change in odor = smells are caused by chemicals!

4. Production of gas = you will see bubbles!

5. Production of a precipitate = a solid formed from liquid mixtures.

5. Conservation of Mass

a. Law of Conservation of Mass: mass cannot be created or destroyed

b. In a chemical reaction, the mass of all the reactants must equal the mass of all the products.

Examples:

10g of ice melt = 10g of water (phys. change)

2.5 kg of wood burn & produce 0.4 kg of ash?

- 2.1 kg of water vapor, carbon dioxide, and other gases released to air

1.5 grams of magnesium ribbon burns and the ashes weigh 2.1 grams

- combined with oxygen in the air to produce magnesium oxide