Chemical Changes & Structure

This section covers the fundamentals of reaction rates and factors that influence them in National 5 Chemistry.

Definition: The rate of reaction is calculated using the formula: rate = Δ quantity / Δ time

Factors that increase reaction rates include:

1. Increasing particle size (for solids)
2. Increasing concentration
3. Increasing temperature
4. Using catalysts

Vocabulary: Catalysts are substances that speed up chemical reactions without being consumed. They can be heterogeneous (different state from reactants) or homogeneous (same state as reactants).

Example: Enzymes are biological catalysts that speed up reactions in living cells.

The section also covers methods for following reactions by measuring changes in concentration, mass, or volume of reactants and products.

Highlight: The rate of reaction at a given stage is calculated using the formula: rate = 1 / t

An example graph is provided to illustrate how to calculate the rate of reaction during the first 120 seconds of a gas-producing reaction.

Overall Summary

National 5 Chemistry Unit 1 focuses on chemical changes, structure, and rates of reaction. Key topics include:

• Factors affecting reaction rates (particle size, concentration, temperature, catalysts)
• Calculating reaction rates
• Periodic table organization and element classification
• Atomic structure and isotopes
• Covalent bonding and molecular shapes

This foundational unit provides crucial knowledge for understanding chemical processes and structures at the National 5 level.