Rate of Reaction 2

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Rate of Reaction - Key Factors

The main factors that affect the rate of chemical reactions are:

Concentration of dissolved reactants

Increasing the concentration increases the frequency (number) of collisions. This increases the rate of reaction.

Pressure of gas reactants

Increasing pressure is like increasing the concentration.
It increases the frequency (number) of collisions. This increases the rate of reaction (makes the reaction faster).

Temperature

Increasing the temperature increases the frequency (number) of collisions.
Increasing the temperature increases the energy of reactant particles. This means that a greater proportion (more) of the particles will have more energy than the activation energy that is needed.
Together, these lead to more successful collisions. This increases the rate of reaction.

Surface area of solid reactants

Increasing the surface area increases the frequency (number) of collisions. This increases the rate of reaction.
This is often done by breaking up solids into smaller lumps (e.g. powders).
This increase in surface area to volume ratio makes sure that more particles are exposed to attack.

Catalysts

Catalysts are substances that increase the rate of a chemical reaction without being used up in the process.

Catalysts

Catalysts increase the rate of chemical reactions by lowering the activation energy. They do this by providing a different reaction pathway.

Not used up

Catalysts are not used up during chemical reactions. This means that:
- They can be reused indefinitely.
- They are not found in chemical equations.
However, catalysts will often need cleaning or regenerating, which has knock-on effects for energy expenditure and environmental impact.

Different catalysts

Different reactions need different catalysts:
- Iron is used in the process that makes ammonia.
- Platinum and palladium are used in catalytic converters in cars.
- Enzymes catalyse reactions in biological systems.

Powders

Catalysts often come as powders, pellets or fine gauzes because these types of substance have particularly high surface areas.

1Biology

1.1Practicals

1.1.1Microscope & Bacteria

1.1.2Bacteria

1.1.3Osmosis Tests

1.1.4Osmosis & Food Tests

1.1.5Enzymes

1.1.6Enzymes 2

1.1.7Photosynthesis & Plant Responses

1.1.8Photosynthesis Experiments

1.1.9Reaction Time

1.1.10Quadrats

1.1.11Decay

2Chemistry

2.1Practicals

2.1.1Salts

2.1.2Neutralisation

2.1.3Titration

2.1.4Electrolysis

2.1.5Electrolysis 2

2.1.6Rate of Reaction

2.1.7Rate of Reaction 2

2.1.8Chromatography

2.1.9Identifying Gases

2.1.10Identifying Gases 2

2.1.11Identifying Ions

2.1.12Carbonates, Halides & Sulfates

2.1.13Flame Emission Spectroscopy

2.1.14Water Purification

2.1.15Water Purification 2

3Physics

3.1Practicals

3.1.1Specific Heat Capacity

3.1.2Thermal Capacity & Insulation

3.1.3Latent Heat

3.1.4Resistance & Current

3.1.5Resistance & Current 2

3.1.6Density

3.1.7Density 2

3.1.8Force & Extension - Springs

3.1.9Waves - Ripple Tank

3.1.10Light

3.1.11Light Reflection & Refraction

3.1.12Radiation

3.1.13Radiation 2

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