Rates of Chemical Reactions
Definition: The speed at which a chemical reaction occurs
Slow Chemical Reactions: Rusting, Ripening, Fermentation
Fast Chemical Reactions: Combustion, Welding
Surface Area
Particle Collision Theory
Temperature
Increasing temperature gives the particles more energy. Therefore, when the molecules collide, they hit harder
Chemical bonds are more likely to break and the atoms in the reactants can rearrange more easily to form products
Increasing the temperature increases the speed of the particles → this causes the particles to collide more frequently, resulting in more chemical reactions occurring in a shorter amount of time
Lowering temperature reduces the rate of chemical reaction. Example: Putting milk in a fridge so that it doesn't spoil
Example: Cooking, as the higher the heat is the aster it will cook. However, sometimes a chemical reaction can occur two fast, such as burning food due to a high temperature
Agitation
Catalysts
Concentration
Collisions between particles are necessary for the reactants to react and form products
It is an extremely common way of increasing the rate of chemical reaction
Particles are more likely to collide and react when there are more particles
You can reduce the concentration (reducing the rate of a chemical reaction)
The rate of the reaction between calcium carbonate and HCI can be increased by crushing the calcium carbonate into smaller pieces
This increases the surface area meaning there are more particles of the calcium carbonate to react with the HCl
They reduce the amount of energy that is required to convert reactants into products
They make it easier for the particles to combine and form new particles
They are also known as chemical helpers
Enzymes
Catalysts are chemicals that speed up chemical reactions, but are not consumed during the reaction
Agitation is the brisk stirring or disturbance of a liquid
Stirring reactants increase the rate of reaction
Agitation ensures that the reactants are kept into contact. This is done by the removing the build up of products around the reactants
It gives the reactants more energy
The build up is removed by keeping the solution moving and ths flushing the products away, thus enabling more reactants to react
A word ending in ‘ases’ is usually an indication of an enzyme
Examples
Enzymes are biological catalysts that naturally speed up chemical reactions in the bod
Amylase
Lipases
Helicase
Cows have a symbiotic relationship with bacteria to break down cellulose
Breaks down starches into simple sugars
Enzymes that digest fats in the gut
Found in saliva
Unravels DNA
Particles are constantly moving
For a chemical reaction to take place, the particles must collide
Activation Energy
Activation Energy is the minimum amount of energy required for a chemical reaction to occur
For a chemical reaction to be successful, the particles which collide must have the right amount of energy