Collision theory Flashcards
What is the collision theory?
The study of how reactions can be sped up/slowed down by changing conditions
What three variables must be present for a reaction occur?
1) Particles must collide
2) with energy higher than the activation energy in order to break the chemical bonds
3) and it must take place between parts of molecules that will actually react together, so the orientation must be correct
If you want a lot of reactions, what condition should you change? (PP + SV)
If you can want a lot of reactions, you need a lot of particles in a small volume
If want a faster reaction rate, what condition should you change? (RM + SM)
If you want to get a faster reaction rate, you would need a lot of rapidly moving particles in a small volume
What are the five factors that affect the rate of chemical reactions?
1) The temperature
2) The concentration of particles
3) The surface area of particles
4) The volume
5) The presence of a catalyst
How does an increase of temperature affect the rate of chemical reactions?
By increasing the temperature, the speed of molecules also increases, which then increases both their kinetic energies and the number of successful collisions
How does an increase of the concentration of reactants affect the rate of chemical reactions?
If there are more molecules particles present in a given volume then collision occurrence increases and the rate of reaction also increases
What eventually happens to the rate of reaction, despite there being an increase in the concentration of reactants?
As the reaction occurs, the reactants are used up and their concentration falls. This results in the rate of reaction eventually dropping a the reaction goes on
How does an increase in the gas pressure affect the rate of a chemical reaction?
By increasing the pressure within a given volume, the particles are forced closer together, increasing the frequency of collisions
How does an increase of surface area of the reactants affect the rate of chemical reactions?
The greater the total surface area of a solid, the more of its particles are available to collide with molecules in a gas or liquid
What are catalysts?
Catalysts are substances that speed up a reaction without being used in the reaction themselves
How does the use of a catalyst affect the rate of chemical reactions?
Catalysts lower the activation energy by providing an alternative reaction pathway, meaning there will be a higher proportion of successful collisions
What is the difference between an exothermic reaction diagram and an endothermic reaction diagram?
An exothermic reaction diagram will show the reactants having more energy than the products whereas in exothermic reactions the products will have more energy than the reactants
How is the term “species” used in chemistry?
CHemists use the term “species” to refer to an atom, molecule or ion
