Ch.5 Physical and Chemical changes

Physical properties

Characteristics that can be determined without changing the composition of the substance e.g. colour mass volume and density

Chemical properties

Characteristics that can be determined only by changing a substances chemical composition - They are related to chemical reactivity of a substance e.g. flammability and likelihood to corrode

Physical change

A change in physical properties of a substance - no new substance is formed

Chemical change

A change in chemical properties of a substance-One or more new substances are formed

What are the physical changes?

Change in physical properties only

No change in chemical composition -no new substance formed

No bonds broken or made

Usually easily reversed

Usually no change in colour PH etc.

What are the chemical changes?

Change in chemical properties

Change in chemical composition- New substance formed

Bonds are broken and made

Usually difficult to reverse

Among other changes there can be changes in colour and pH. A precipitate or gas may be formed (fizzing may be observed)

Law of conservation of mass

The total mass of the products of a chemical reaction is equal to the total mass of the reactants

Law of conservation of Energy

State’s that Energy is neither created nor destroyed but simply changes from one form to another