Collision Theory Flashcards
What is collision theory? The theory that …
So to react particles must…?
…rate of reaction depend son how often and how hard reacting particles collide with each other
Collide together with enough energy to react
More collisions …. the …. of ….
increases the rate of reaction
The effects of temp, surface area, and concentration can be explained by what?
How often the reacting particles collide successfully
What happens to the number of collisions under higher temperature?
What happens to the particles when temperature is increased?
So how does this affect their collisions?
The increase in frequency
They move faster
They occur more frequently, they collide more often
What happens to the number of collisions under higher concentration or pressure?
What happens if a solution is made more concentrated?
What does increasing the pressure in a gas mean?
They increase
There are more particles of reactant between the water molecules in the aqueous, which makes collisions of the actual reactant particles more likely therefore more frequent.
The particles are closer together so there will be more frequent collisions.
What happens to the number of collisions when there is a larger surface area?
If one of the …. is a ….. then breaking it up into … pieces will … its …. …. area.
What happens if this happens?
They increase
reactants, solid, small, increase, total surface
The particles around the solid in the solution will have more area to work on so there’ll be more frequent collisions
Faster collisions …?
Increasing the temperature causes…
Reactions only happen when…
increase the rate of reaction
… faster collisions
… the particles collide with enough energy
What does higher temperature do to the collisions?
It increases the energy of the collisions because it makes all the particles move faster
The minimum amount of energy needed by the particles to react is called what?
At …. temps there will be more particles ….. with enough … to make the reaction happen.
The activation energy
higher, colliding, energy
What is a catalyst?
A substance which speeds up a reaction, without being used up or changed in the reaction
How does a solid catalyst work?
It gives the reacting particles a surface to stick to therefore increasing the number of successful collisions between particles, so it speeds up the reaction
How do catalysts help to reduce costs in an industrial reaction? (3)
- They increase the rate of reaction saving a lot of money as the machine doesn’t need to operate for so long to produce the same amount of product.
- The reactions will work at a lower temperature reducing the energy needed, good for cost and sustainable development
- They never get used up
What are the disadvantages to using a catalyst industrially? (4)
- Expensive to buy
- Often need to be removed from the product to be cleaned
- Different reactions require different catalysts meaning many will be needed for a plant
- They can be poisoned by impurities and stop working so the reaction mixture must be kept clean
Whenever chemical reactions occur, energy ….
…is transferred to or from the surroundings
In an exothermic reaction … is …. ….
heat is given out
What is an exothermic reaction?
One that gives energy out to the surroundings usually in the form of heat and is usually shown by a temperature rise.
What are three examples of an exothermic reaction?
Burning fuels
Neutralisation reactions
Oxidation reactions
What happens in the exothermic reaction where fuel is burned? (simple)
Combustion, it gives out a lot of heat
What happens in the exothermic reaction of neutralisation?
Acid + alkali gives out a lot of heat
What happens in the exothermic reaction of oxidation, using an example?
Sodium + water produces heat, the sodium emits heat and moves about on the surface of the water as it’s oxidised.
How do hand warmers work?
How do self heating hot chocolate and coffee cups work?
An exothermic reaction of iron and air, with a salt catalyst generates heat.
They rely on exothermic reactions in the chemcials in the bases of the cans
In an endothermic reaction heat is….
taken in
What is an endothermic reaction?
One that take sin energy from the surroundings usually in the form of heat and is usually shown as a fall in temp.
How common are endothermic reactions?
What is a common example, of one?
Less common than exo.
Thermal decomposition.
Give an example of a thermal decomposition reaction?
- What is supplied
- What are the reactants and what happens (symbol equation)
- Heat must be supplied to make the calcium carbonate decompose to make quicklime.
- CaCo3 (to)= CaO + CO2
What is one every day use of an endothermic reaction?
Sports injury packs take in heat making their surroundings very cold, more convenient than ice.
What energy transfer is in a reversible reaction?
Endothermic and exothermic, one in one direction, one in the other
The energy absorbed by the …… ….. is … to the energy released by the …. ….. .
endothermic reaction is equal, exothermic reaction
What is a good example of a reversible reaction?
What happens using what energy transfers?
Thermal decomposition of hydrated copper sulphate
Hydrated copper sulphate to anhydrous copper sulphate and water, exothermic, gives out energy, the other way round takes it in.
Describe the thermal decomposition of hydrated copper sulphate… (2)
Heating the blue copper crystals evaporates the water and leaves white crystals, this is endothermic.
If you add some water to the white crystals you get the blue ones again, this is exothermic.
