Study Notes
Chemical reactions involve the transformation of substances into new products, which are not easily reversible. Reactants — substances that undergo change in a chemical reaction. Example: In the reaction of hydrogen and oxygen, hydrogen and oxygen are reactants. Products — new substances formed as a result of a chemical reaction. Example: Water is the product when hydrogen reacts with oxygen. Combustion — a reaction where a substance burns in oxygen, releasing energy. Example: Methane burning in a bunsen burner. Thermal Decomposition — a reaction where one reactant breaks down into two or more products. Example: Copper carbonate decomposing into copper oxide and carbon dioxide. Word Equation — a representation of a chemical reaction using the names of the substances involved. Example: Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide. Neutralisation — a reaction between an acid and an alkali to form a salt and water. Example: Hydrochloric acid reacting with sodium hydroxide to form sodium chloride and water.
Exam Tips
Key Definitions to Remember
- Reactants: Substances that undergo change in a chemical reaction.
- Products: New substances formed as a result of a chemical reaction.
- Combustion: Reaction where a substance burns in oxygen, releasing energy.
- Thermal Decomposition: Reaction where one reactant breaks down into two or more products.
- Word Equation: Representation of a chemical reaction using the names of the substances involved.
Common Confusions
- Confusing reactants with products in a chemical equation.
- Thinking that all chemical reactions are reversible.
Typical Exam Questions
- What is a word equation? A representation of a chemical reaction using the names of the substances involved.
- What happens in a combustion reaction? A substance reacts with oxygen, releasing energy.
- What is produced in a neutralisation reaction? A salt and water.
What Examiners Usually Test
- Ability to identify reactants and products in a chemical equation.
- Understanding of different types of chemical reactions, such as combustion and thermal decomposition.
- Knowledge of how to write and interpret word equations.