Chemical reactions and writing chemical equations 7.1-7.2

Sammy YellenIman Aly

Alyssa West

What is a Chemical Reaction?

The changing of substances to other substances by the breaking of old bonds and the formation of new bonds.• Take place in and around you.• Necessary to sustain life.• Not all chemical reactions involve living things.Examples- digesting your food, plant growth, and car batteries.

Reactants- a starting substance in a chemical reaction.

Products- a substance formed in a chemical reaction.

Reactants ProductsOne or more substances, the reactants, change into one or more new substances, the products.ExamplesIron + Oxygen iron (III) oxideHydrogen peroxide water + oxygenMethane + Oxygen carbon dioxide + water

Extra Facts

• Many chemical reactions are non-reversible changes.

• When gas nitrogen dioxide is heated, a chemical reaction changes the brown nitrogen dioxide gas into two colorless gases (nitrogen monoxide and oxygen). If these colorless gases are cooled, they will change into brown nitrogen dioxide gas. This is one of the few reversible changes.

Skeleton Equations

A chemical equation that doesn’t indicate the relative amounts of the reactants and

products.

How to Write Skeleton Equations

• To write a skeleton equation, you have to write the formulas for the reactant and the product.

• Then, put the reactant on the left of the arrow, and then the product on the right.

Example:Fe + O₂ Fe₂O₃

Writing Equations

Catalyst- substance that speeds up a reaction without being used up. MnO₂H₂O₂ (aq) H₂O (l) + O₂ (g)

Some examples are nickel catalysts and platinum catalysts.

Write the skeleton equation for when iron and sulfur form Iron (II) Sulfide

Write the skeleton equation for when iron and sulfur form Iron (III) Sulfide

Fe + S → FeS

Fe + S → Fe₂S₃

Homework

1. What’s the difference between a reactant and a product?

2. Write a skeleton equation for this chemical reaction:magnesium reacts with oxygen to form magnesium oxide.