Chemical Reactions

A. Matter can change physically or chemically; a process that produces a chemical change is a chemical reaction

B. A chemical equation is a shorthand form of what reactants are used and what products are formed in a chemical reaction

1. Some use words or chemical names to identify the products and reactants

Ex: Iron + Oxygen + Water Rust

2. Chemical formulas can represent chemical names in an equation

Ex: Fe + H2O FeO2 + H2

C. The mass of the reactants and products in a chemical reaction is always the same due to the Law of Conservation of Mass

D. Chemical equations are balanced when the number of atoms is the same on each side of the equation

Ex: Fe + 2H2O FeO2 + 2H21 iron atom

1 iron atom

2 oxygen 2 oxygen

4 Hydrogen

4 Hydrogen

1. In a chemical equation the reactants (substances going into reaction) are on the left and the products (substances being produced) are on the right

Ex: Fe + 2H2O FeO2 + 2H2

Reactants Products

E. Energy is released or absorbed during a chemical reaction

1. Exothermic reactions – release energy

2. Endothermic reactions – absorb energy

A.Different chemical reactions take different amounts of time

B.Activation Energy – the amount of energy needed to start a reaction

C. The rate of reaction measures how quickly a reactant is disappearing and how quickly a product is appearing

1. Tells how quick a substance changes per unit time

2. Important in industry; the faster a product can be made the lower the cost

3. Factors that change reaction rates:

a) Temperature – higher temp. faster particles are move and collide which makes reactions happen more quickly

b) Concentration – amount of substance per volume

c) Particle size/Surface area – more surface area the faster the rate due to more area to react

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D. Inhibitor – a substance that slows down the rate of a chemical reaction

E. Catalyst – a substance that speeds up the rate of reaction

ex: Enzymes – special proteins in the human body