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.