Regents Chemistry Review By Topic: Introduction to Chemistry

There are three phases of matter.

Solids : have definite shape and volume

Liquids: have definitely volume but take the shape of the container

Gases: take the volume and shape of the container

Substances

There are two types of substances: elements and compounds.

Elements

• all of the elements can be found on the Periodic Table

• Table S lists the names of all of the elements

• elements can not be broken down by chemical means

• Examples: Fe, Na...

Compounds

• consist of atoms of two or more elements in fixed ratio

• can be broken down by chemical means but not by physical

• Examples: NaCl, H2O

• different compounds have different chemical and physical properties

Mixtures

• consist of two or more substances (elements or compounds)

• can be broken down physically

• can be homogeneous (uniform composition such as salt in water) or heterogeneous (nonuniform composition such as sand)

Chemical properties/changes

During a chemical change the identity of a substance changes. A chemical change represents a reaction. Chemical property refers to the reactions that the substance can do. Examples of chemical properties are: burning of wood, reaction of metal with water etc.

Physical properties/changes

Physical change does not change the identity of a substance but may change the phase or appearance of a substance. For example: melting ice, grinding chalk, etc.

Distillation:

Laboratory technique that separates two liquids based on their boiling points.

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