C8.2 - Collision theory and surface area Flashcards
In everyday life, you often do what without thinking about it?
In everyday life, you often control the rates of chemical reactions without thinking about it
In everyday life you often control the rates of chemical reactions without thinking about it.
Examples
For example,:
1. Cooking cakes in an oven
Or,
2. Adding more detergent to a washing machine
What affects the rate of chemical reactions?
There are 4 main factors which affect the rate of chemical reactions:
- Temperature
- Surface area of solids
- Concentration of solutions, or pressure of gases
- The presence of a catalyst
Reactions can only take place when what?
Reactions can only take place when the particles,: 1. Atoms 2. Ions Or, 3. Molecules ,of reactants come together
Reactions can only take place when the particles, atoms, ions or molecules, of reactants come together.
The reacting particles do not only have to bump into each other, but also need to do what?
The reacting particles do not only have to bump into each other, but also need to collide with enough energy to cause a reaction to take place
Reactions can only take place when the particles, atoms, ions or molecules, of reactants come together.
The reacting particles do not only have to bump into each other, but also need to collide with enough energy to cause a reaction to take place.
What is this known as?
This is known as collision theory
Collision theory
Collision theory is an explanation of chemical reactions in terms of reacting particles colliding with sufficient energy for a reaction to take place
Activation energy
Activation energy is the minimum amount of energy:
- That particles must have before they can react
- Needed for a reaction to take place
Reactions are more likely to happen between reactant particles if you do what?
Reactions are more likely to happen between reactant particles if you increase the:
- Frequency of reacting particles colliding with each other
- Energy they have when they collide
If you increase the chance of particles reacting, you will also do what?
If you increase the chance of particles reacting, you will also increase the rate of the reaction
What is the collision theory used to explain?
The collision theory is used to explain:
- How reactant particles, atoms, molecules or ions, react together
- Why their rate of reaction can vary
When lighting a campfire, what is it not a good idea to do?
When lighting a campfire, it is not a good idea to:
- Pile large logs together
- Try to set them alight
When lighting a campfire, it is not a good idea to pile large logs together and try to set them alight.
What do you do to begin with?
You use small pieces of wood to begin with
When lighting a campfire, it is not a good idea to pile large logs together and try to set them alight.
You use small pieces of wood to begin with.
What does doing this do?
Using small pieces of wood to begin with increases the surface area of the wood
When a solid reacts in a solution, what affects the rate of the reaction?
When a solid reacts in a solution, the size of the pieces of solid affects the rate of the reaction
When a solid reacts in a solution, why do the sizes of the pieces of solid affect the rate of the reaction?
When a solid reacts in a solution, the size of the pieces of solid affects the rate of the reaction, because the particles inside a large lump of solid are not in contact with the reactant particles in the solution
When a solid reacts in a solution, the size of the pieces of solid affects the rate of the reaction, because the particles inside a large lump of solid are not in contact with the reactant particles in the solution, so they cannot react.
What do the particles inside the solid have to do?
The particles inside the solid have to wait for the particles on the surface to react first before they:
- Are exposed
- Have a chance to react
When a solid reacts in a solution, the size of the pieces of solid affects the rate of the reaction, for example the particles inside a large lump of solid.
What happens in smaller lumps, or in a powder?
In: 1. Smaller lumps Or, 2. A powder ,each tiny piece of solid is surrounded by solution
In smaller lumps, or in a powder, each tiny piece of solid is surrounded by solution.
What happens?
Many more particles of the solid are:
- Exposed
- Able to react at a given time
You can compare solids with different surface areas quantitatively by what?
You can compare solids with different surface areas quantitatively by looking at their surface area to volume ratio (SA : V)
You can compare solids with different surface areas quantitatively by looking at their surface area to volume ratio (SA : V).
What happens the smaller the size of the pieces of a solid material?
The smaller the size of the pieces of a solid material, the larger its surface area to volume ratio
What happens as the side of a cube decreases in size by a factor of 10?
As the side of a cube decreases in size by a factor of 10, its surface area to volume ratio increases by 10
As the side of a cube decreases in size by a factor of 10, its surface area to volume ratio increases by 10.
What do you get for the same volume of material?
You get a larger surface area of reactant particles exposed for the same volume of material
As the side of a cube decreases in size by a factor of 10, its surface area to volume ratio increases by 10.
You get a larger surface area of reactant particles exposed for the same volume of material.
So what happens the larger the SA : V?
The larger the SA : V, the faster the reaction
What do particles do all the time?
Particles collide all the time
Particles collide all the time, but only some collisions lead to reactions.
What does increasing the number of collisions in a certain time and the energy of collisions do?
Increasing the:
1. Number of collisions in a certain time
2. Energy of collisions
produces faster rates of reaction
Particles collide all the time, but only some collisions lead to reactions.
Increasing the number of collisions in a certain time and the energy of collisions produces faster rates of reaction.
What does a larger surface area not result in?
A larger surface area does not result in collisions with more energy
When lighting a campfire, it is not a good idea to pile large logs together and try to set them alight.
You use small pieces of wood to begin with.
Using small pieces of wood to begin with increases the surface area of the wood.
This results in what?
This results in more wood being exposed to react with oxygen in the air
When a solid reacts in a solution, the size of the pieces of solid affects the rate of the reaction, because the particles inside a large lump of solid are not in contact with the reactant particles in the solution, so they what?
When a solid reacts in a solution, the size of the pieces of solid affects the rate of the reaction, because the particles inside a large lump of solid are not in contact with the reactant particles in the solution, so they cannot react
In smaller lumps, or in a powder, each tiny piece of solid is surrounded by solution.
Many more particles of the solid are exposed and able to react at a given time.
This means what?
This means that reactions can take place much more quickly
Particles collide all the time, but only some collisions lead to what?
Particles collide all the time, but only some collisions lead to reactions
Particles collide all the time, but only some collisions lead to reactions.
Increasing the number of collisions in a certain time and the energy of collisions produces faster rates of reaction.
A larger surface area does not result in collisions with more energy, but does increase what?
A larger surface area does not result in collisions with more energy, but does increase the frequency of collisions
