The Classification of Matter…it matters

(Ch. 2)

2.1 Matter

• Matter has mass and volume.– The smallest particles in matter are called atoms.– All matter is made of atoms.

• A molecule is made up of two or more atoms stuck together. Ex: H2, H2O. A molecule can be a compound or an element.• A particle is one small unit of matter.• Example: A molecule or an atom

Matter

• An element is ONE type of atom. Ex: gold contains only gold atoms. Ex: H2, Au

• A compound is a substance that contains two or more types of atoms. – Ex. CO2

– A compound always has the same number of atoms in each molecule.

States of MatterSolid Liquid GasDefinite shape Indefinite shape Indefinite shapeDefinite volume Definite volume Indefinite volume

2.2 Properties of Matter

• Physical properties include odor, color, volume, state (gas, liquid, solid), density, melting point, and boiling point.

• Chemical properties refer to the ability of a substance to form a new substance. Ex: Iron reacts with water and makes rust (iron oxide).

2.2

• When you melt ice or boil water, the state of water changes. But the molecules of H2O are still there.

• A physical change does not change the composition of the substance: phase changes (melting, freezing, boiling, condensing, sublimation), breaking, bending.

• In a chemical change, a substance changes into one or more new substances. Example: Burn, rust, rot– Transfer of energy (heat, light)

• Burning wood

– A change in color• Eggs cooking

– A gas being produced• Burning wood

– The appearance of a solid.

Chemical Change

• When electricity passes through water, the water changes into hydrogen gas and oxygen gas.

• Are the molecules of H2O still there after the change?

• No, they’re not.

Quiz: Physical or chemical change?

Chemical. Baking soda combines with vinegar to make carbon dioxide, acetate and water.

2.3 Classifying matter

• A mixture has more than one substance.– Ex.: Air contains many gasses: nitrogen,

oxygen, water, argon, carbon dioxide…

• How is air in the city different from air in the country?

• Can you think of other examples?

2.3 Classifying matter

• Mixtures of metals are called alloys. – Ex. Brass is a mixture of copper and zinc.

 

• Pure substances contain only one substance. They can be elements or compounds. Ex: H2O, H2

• Heterogeneous mixtures have different parts, and each part has different propertiesEx: Sand and water.

• A mixture can be separated into pure substances.

• A heterogeneous mixture can be separated by filtration.

2.3 Classifying matter

• Homogeneous mixtures or “solutions” have the same composition throughout.– All parts look the same.– Particles are too small to see.

Heterogeneous or Homogeneous (solution)

Hint: What are the beams of light hitting?

• For example, seawater is a mixture of salt and water. The salt can be separated from water by distillation.

Distillation is the separation of a mixture by boiling the liquid and condensing the gas. When sea water is boiled, the salt stays in the container, while the steam escapes.