Physical and Chemical Changes

A chemical reaction is a process in which one or more substances undergo chemical change and produce new substances, and their chemical composition is altered

There are two kinds of changes

Physical: A change in appearance, size, shape, or state — the chemical identity is the same. Some examples include cutting paper, water boiling, and ice melting

Chemical: A change in the chemical composition, and one or more new substances are formed. Some examples include rust, burning a match, and baking.

Reactants (substances before reaction) → Products (new substances after)

The Law of Conservation of Mass states that matter cannot be created or destroyed in an ordinary chemical reaction.

There are two types of systems in which a chemical reaction can occur in

Open: Gas is able to escape. Measured mass from before and compared to end may decrease but total mass is still conserved. Missing mass may have left as gas

Closed: Gas can not escape. Even if bubbles form, total measured mass of sealed system stays same before and after