What is a chemical reaction? -a process in which a substance changes into an entirely different substance. Two main components of a chemical reaction are a: Reactant Product

Reactants vs Products Reactants – the starting materials in a reaction (what we start with) Products – are the materials produced from the reaction (what we end with)

The arrow always points to the products Reactants Products The arrow always points to the products

2H2 + O2 2H2O C + O2 CO2

Chemical Reaction During a chemical reaction, the reactants and the products have the same atoms. They just rearrange partners and switch partners. Chemical bonds break in the reactants and new chemical bonds form in the products.

Why must both the reactant and the products have the same number and kinds of atoms? It’s the law – the law of conservation of mass Matter cannot be created or destroyed In every chemical reaction, the mass of the matter in the products must equal the mass of the reactants.

Law of Conservation of Mass Matter can’t be created or destroyed The mass of the products must equal the mass of the reactants. Same number/kinds of elements on both sides

How A Reaction Works

CH4 + H2O CO + 3H2 CO + H2O CO2 + H2 The arrow always points to the products

Energy in a Reaction Endothermic Reaction – a chemical reaction that absorbs heat energy from its environment. Exothermic Reaction – a chemical reaction that releases heat energy to its environment

Endothermic Exothermic Melting Ice Boiling Water Baking Bread Cooking an Egg Burning a match Ice Forming Calcium Chloride with Water (Did in class) Mixing water with strong acids.

Photosynthesis – the process of turning sunlight into food Light energy to chemical energy 6CO + 6H20 C6H12O6 + 6O2 Respiration (Cellular Respiration) – the process of turning sugar and oxygen into carbon dioxide and water. C6H12O6 + 6O2 6CO + 6H20

Reactions Rates Think of rate as how fast or slow the reaction happens What factors influence how fast a reaction happens?

4 Factors that Influence Reaction Rates Temperature or reactants Concentration of reactants Surface area of reactants Presence of a catalyst

Temperature of Reactants Higher temperatures react faster than cooler temperatures

Concentration of Reactants Concentration is the number of particles in a given volume The higher the concentration the faster the reaction The lower the concentration the slower the reaction

Surface Area of Reactants The more surface (matter) area exposed the faster it reacts Presence of a Catalyst Something we add to a reaction to speed it up. IS NOT a reactant and is not consumed in the reaction. It DOES NOT take part or participate in the reaction.