2.11 Describing Chemical Reactions

(Sec 9.1 pg 231-234)

• We have learned a lot about how to classify compounds into different groups – see Fig.1 p.231.

• A chemical reaction is any process that involves a change in the chemical properties of the compound (remember – chemical changes happen when new substances are formed; physical changes do not create new substances).

• We can represent a chemical reaction with a chemical equation.

• A chemical equation uses chemical formulas to represent what happens in a reaction.

• The compounds you have initially are called reactants, the compounds that you end up with are called products (Fig.5 p.232).

• Chemical reactions follow certain laws. – One of these laws is the law of conservation of mass,

which states that matter is neither gained nor lost during a chemical reaction.

– In other words “what goes in must come out”.

• Chemical reactions follow certain laws. – In terms of chemical reactions, the # of atoms of each

element in the reactants will equal the # of atoms of that same element in the products, but they will be re-arranged.

• Take a look at the reaction below.....what’s wrong with this picture???

• How can we fix it???