Example:Boiling water.Melting ice.Mixing sand and water.Tearing a piece of aluminum foil.

Physical Changes

Physical change = a change in one or more physical properties. Does not change the composition of the substance.

Does not create a new substance.

Is easily reversed.

Example:RustingBurning woodCooking an egg

Chemical Changes

Chemical change = a change in the composition of the substance. A chemical change changes the substance into a different substance or substances.

Ways to identify chemical changes.

1. Color change

2. Production of gasses

3. Odor change

4. Production of solids (Precipitate)

5. Light

6. Temperature change

Pure Substances and Mixtures

Matter can be classified into two categories: Pure substances or mixtures.

Review: What are the two characteristics of matter?

Has variable composition

Example: Soda, steel, air

Always has the same composition.

Example: Pure water, aluminum, table salt.

Pure Substance

Mixture

A mixture is a type of matter that is made up of more than one kind of particle. It contains two or more pure substances.

A pure substance is a type of matter that is made up of only one kind of particle.

Matter

MixturePure substance

Pure substances can either be compounds or elements.Elements are pure substances that are only made up of one type of atom.

-Cannot be broken down into other substances by chemical means.

-Example: oxygen, aluminum

Compounds are pure substances that are made up of two or more types of atoms chemically bonded together.

-Always have the same composition.

-Example: Water is a compound. H2O. Water always has 2 hydrogen atoms with 1 oxygen atom.

CompoundElement

Matter

MixturePure substance

A mixture can be homogeneous or heterogeneousA homogeneous mixture is the same throughout.

- Also called a solution

-Example: Dissolve salt in water.

A heterogeneous mixture is not uniform throughout. Different regions have different properties.

-Example: Sand in water. Some regions contain more sand.

HeterogeneousHomegeneous

CompoundElement

Matter

MixturePure substance

Separating MixturesWe can separate mixtures using a variety of methods. Three ways we will talk about in class today are

1. Distillation

2. Filtration

3. Chromatography

Distillation is the separation of mixtures using differences in boiling point or volatility.

We can then condense the vapors (gas) to its liquid form and collect the separated substance.

For example: You have a glass of salt water. You can boil off the water, condense the water vapor, and collect liquid water.

Filtration is used to separate a mixture of a solid and a liquid. As the liquid passes through a filter, the solid particles get trapped.

Example:

Chromatography is the separation of mixtures based on the affinity (attraction) of a substance to either a stationary phase or mobile phase.

Example: Separating out ink on filter paper.

http://www.youtube.com/watch?v=mLbdHPBC2I4