Unit 1 - Rates of Reaction T1 Flashcards
Factors affecting reaction rate
Temperature, concentration, particle size and use of a catalyst.
Collision theory
For a reaction to occur, the particles that are reacting must collide with each other. Only some of all the collisions that take place cause a chemical change to happen. These are called ‘successful’ collisions. The greater the number of ‘successful’ collisions, the faster the rate of a reaction. This is called the ‘collision theory’.
Temperature
If the temperature is increased, the particles have more energy and so move quicker. Increasing the temperature increases the rate of reaction because the particles collide more often and with more energy. The higher the temperature, the faster the rate of a reaction will be.
Particles at high temperatures move faster than particles at low temperatures.
Drawing rate graph.
When asked to draw a rate graph, if you are doing something that will increase the rate of reaction draw a line that is steeper but levels off at the same point.
Something slower will be less steep than original line but still level off at the same point.
Concentration
If the concentration of reactants is increased, there are more reactant particles moving together. There will be more collisions and so the reaction rate is increased. The higher the concentration of reactants, the faster the rate of a reaction will be.
A higher concentration results in a greater number of successful collision
Particle size
By decreasing the particle size of a reactant, we are increasing its surface area. The greater the surface area, the higher the chance of collisions, thus the faster the rate of reaction. The smaller the particle size the faster the reaction.
Use of a catalyst
A catalyst speeds up the rate of a reaction but it is not used up in the reaction. If a catalyst is present, the reacting particles can collide more successfully with less energy and so the reaction can take place at a lower temperature.
Monitoring the rate of reaction of reaction
The rate of a chemical reaction is a measure of how fast the reactants are being
used up and how fast the products are being made. The rate can be determined by measuring:
changes in the concentration of the reactants or products
changes in the mass of the reactants or products
changes in the volume of the reactants or products
Monitoring reaction rate when gas is produced example.
Since a gas - (insert gas here) is released, a gas syringe could be used to monitor the rate of reaction.
Draw a labelled diagram of experiment. Comical flask with solution in bottom, and reactant put in it. Draw gas rising through flask and into syringe, with lines to indicate scale. Make sure experiment is plausible - no blockages.
Use stopwatch to time until the syringe stops moving, once time is taken measure how much gas was in the syringe. I.e. 30cm3. Then use rate equation to calculate rate. Rate = delta Quantity over delta time.
Give example for what rate could be (make up numbers)
Sketch rate graph.
Determining rate from a graph.
Read scale, draw lines from times measures to make rectangle. Read scales and input those into rate equation.
Units for rate of reaction.
What measurable quantity is, I.e g, cm3, moll-1, per second. For example gs-1, or cm3s-1
A chemical reaction can be recognised by
And what happens during them
Colour change, energy change, a gas being given off or a solid being formed.
In all chemical reactions a new substance is formed called the product
Exothermic reaction
Energy EXits, meaning temperature of surrounding increases.
Endothermic reaction
Where energy ENters the reaction, which means the temperature of the surroundings decreases.
Rate of reaction
Measure of the speed of the reaction.
