Changing Matter• Matter can be changed two ways:

–Physically • Physical reaction

• Physical change

–Chemically• Chemical reaction

• Chemical change

Physical Changes

• Do NOT CHANGE THE TYPE OF MATTER

– Nothing new or different is formed– Could be a change in:

• Mass

• Volume

• Hardness

• Color

• Density

How to Recognize a Physical Change

• Change in. . .– Size– Shape– State

Examples of Physical Changes

• Boiling • Freezing• Dissolving • Breaking • Making a mixture

– 2 or more types of matter (substances) mixed together

• Not in specific amounts• Can be separated physically

Chemical Properties

• Describes how a substance reacts

• Examples:– What happens when

it’s burned?– What happens when

it’s mixed with vinegar?

Chemical Changes

• Evidence of a chemical reaction– Formation of gas (bubbles form)– Formation of precipitate (new substance)– Change in color– Change in energy (heat and light)

• Endothermic– Absorbs heat energy (gets cold)

• Exothermic– Releases heat energy (gets hot)

Examples of a Chemical Change

• Burning anything• Rusting• Tarnishing• Baking a cake• Frying eggs

Chemical Changes

• Atoms are re-arranged, NOT created or destroyed– Law of Conservation of Matter– Law of Conservation of Mass

Chemical Changes

• Matter is conserved type of atoms does not change– Nothing is created or destroyed

• Mass is conserved amount of atoms cannot change– Nothing is created or destroyed

Chemical Changes

• To show conservation of mass Balance equations– Make sure there are the same number of

each type of atom in the products and in the reactants

Balancing Equations

The equation for the burning of methane gas in oxygen is:

CH4 + 2 O2 → CO2 + 2 H2O

Subscript

Shows # of atoms

Coefficient

Shows # of molecules

Balanced Equation

CH4 + 2 O2 → CO2 + 2 H2O

Reactants Products (Original Substances) (New Substances Formed)

Types of Chemical Reactions

• Synthesis Reaction2 or more simple substances combine to form a more complex substance.

A+B AB

• Decomposition Reaction

A more complex substance breaks down into its more simple parts

AB A + B

Types of Chemical Reactions

• Replacement Reactions

AB + CD AD + CB