kinetics Flashcards
what is kinetics
Kinetics is the study of the factors that affect the rates of reaction
what is rates of reaction
the rate of reaction is how quickly the reaction takes place
are all rates of reactions the same
There is a large variation in reaction rates
e.g. popping a test tube full of hydrogen is over in a fraction of a second
complete rusting of an iron nail could take several years
how can you change the speed of a reaction
reactions can be sped up or slowed down by changing the conditions of the reaction
what must happen for a reaction to take place
for a reaction to take place between two particles they must collide with enough energy to break bonds
where must the collision take place
The collision must take place between the parts of the molecule that is going to react together.
Therefore orientation has a part to play
How do you get a lot of collisions
you need a lot of particles in a small volume
how do particles get enough energy to break bonds
for the particles to have enough energy to break bonds, they need to be moving fast.
how can we have a fast reaction rate
A fast reaction rate requires rapidly moving particles and a small volume
do all collisions between particles lead to a reaction
most reactions btween molecules or oher particles do not lead to a reaction because:
they do not have enough energy ( to break the bonds )
they are in the wrong orientation
what effects the rates of chemical reactions
increasing the temperature
increasing the concentration of a solution
increasing the pressure of gas reaction
increasing the surface area of solid reactants
using a catalyst
how does increasing the temperature affect the rate of chemical reaction
increases the speed of the molecules which in turn increases their energy and the number of collisions
how does increasing the concentration of a solution affects the rate of chemical reaction
more particles present in a given volume then more collisions are more likely to happen and the reaction would be faster
how does increasing the pressure of a gas reaction effect the reaction
same effect as increasing concentration of a solution
more molecules or atoms in a given volume so more collisions are likely therefore speeding the reaction up
how does increasing the surface area of a solid reactant effect the rate of reaction
the greater the surface area of the solid, the more of its particles are available to collide with molecules in a gas or liquid. This means that breaking a solid lump into smaller pieces increases the rate of its reactions because there are more sites for reaction
what is a catalyst and how does it effect the rate of reaction
a catalyst is a substance that can change the rate of a chemical reaction without being chemically changed itself
what must happen for a collision to result in a reaction
the molecules must have a certain minimum energy, enough to start breaking bonds. This energy is called the activation energy
what is an exothermic reaction
exothermic reactions transfer energy from molecules to the surroundings. This causes the surroundings to heat up
what are some examples of exothermic reactions
- combustion
2. certain oxidation and neutralization reactions
how does a reaction profile/ enthapy diagram look like for a exothermic reaction
Products have less energy than the reactants. This is because energy is being transferred from reaction to the surroundings
The difference between the reactants and the energy in the products tells us the energy that is being released to the surroundings
what are some uses for exothermic reactions
- hand warmers
2. self heating cans e.g. for food and drinks
what is an endothermic reaction
endothermic reactions take in energy from their surroundings therefore, the temperature of the surroundings get decrease [ get colder].
what are some examples of endothermic reactions
thermal decomposition
how does an energy profile/ enthapy look like for a endothermic reaction
Products have more energy energy than reactants because energy is being taken in from the surroundings
The difference in energy between the reactants and products tells is the amount of energy taken in by the reaction