Rates of Reaction
Rates of reaction
The Effect of Surface Area
Substances react by colliding with enough energy.
- Large surface area - more collisions.
- More collions = higher proportion of successful collisions, so the higher the rate of reaction.
The Effect of Temperature.
- Particles have more kinetic energy.
- Particles move around faster.
- Collision occur more frequently and will be harder. Therfore more successful, increasing the rate of reaction.
The higher the temperature, the faster the rate of reaction.
The Effect of Concentration
- More particles in a volume (cm3)
- Therefore, more collisions per second;
- The more collisions, the higher proportion of successful collisions;
- So, rate of reaction increases.
Low concentration = few collisions
High concentration = more collisions
The Effect of Catalysts
A catalyst speeds up the rate of a chemical reaction, without being used up it's self.
- Catalysts make chemical processes energy efficient - they can be re-used and so save the energy that would used to create high temperatures.
How do they work?
- Catalysts aDsorb (attatches) the reactants onto their surface, therefore making them more likely to react.
- For collisions to be successful, they must occur with enough energy. This is known as the ACTIVATION ENERGY
- Catalysts work by lowering the activation energy.
Measuring Rates of Reaction.
There are two ways to measure 'Rates of Reactions':
- Measure the rate at which a reactant is used up.
- Measure the rate at which a product is formed.
Things to measure:
- The mass of a substance.
- The volume of a gas is usually measured with a gas syringe, or sometimes an upside-down measuring cylinder or burette.