The Problem: I am going to find out how temperature can affect the rate of reaction.
Factors that change the rates of reactions are:
Temperature – an increase in temperature will make the reaction occur faster. This happens because the particles of that substance move faster when it is heated. Because the particles move faster, they would collide more, making the reaction rate faster.
Concentration – the increase in concentration, the greater and faster the reaction. This is because if the solution is more concentrated, it will increase the number of molecular collisions.
Surface area: if the solid reactant is crushed up into smaller pieces, it will increase the total surface area, which means there are more particles to react with the other reactant in the solution.
Catalyst: this is a substance which increases the speed of a reaction, without being changed or used up in the reaction.
For a chemical reaction to take place, some bonds in the reactants must be broken. The colliding particles must have enough energy to break these bonds. This minimum amount of energy is called the activation energy. Only the very fastest moving particles have enough energy to break bonds.
In gases, liquids and in solution, the particles move at a range of speeds. Some are moving very slowly and others are moving very fast. To react, particles must collide with enough energy and in the correct orientation for bonds to be broken.
(The information above is from research I have done from the Internet, revision book and from my own knowledge)
Prediction: My prediction for this investigation is the higher the temperature, the faster the reaction. This is because the atoms will move faster and that will cause the particles to collide faster and bonds to break faster than usual.
Reaction: The reaction I am going to use is:
Sodium Thiosulphate + Hydrochloric AcidSodium Chloride + Sulphur Dioxide + Water + Sulphur. (Na2 S2 O3 + 2HCl 2Na Cl + SO2 + H2O + S)
This reaction is easy to time because the solution goes cloudy and yellow.
Apparatus: The apparatus I will use is as follows.
Piece of paper (to draw cross on),
Basic Method: I will first lay out all the apparatus I need. I will set them up (as below) with the substances at different temperatures. As soon as I put Sodium Thiosulphate and Hydrochloric Acid in the flask(along with 40ml of distilled water), I will begin the stopwatch and time how long it takes for the reaction to occur. I will look from the top and wait for the cross to disappear. When that happens, I will stop the stopwatch and record the time.
Safe test: I will have to do a few things in order to make my experiment safe. Firstly all stools should be tucked under the tables and bags should be out the way (so no-one will fall over them). I will have to be careful when the Bunsen burner is on and make sure the flame is visible when not in use (This is so other people can see it is on). Goggles could be worn but are not essential. After the beaker is heated I will use a folded up paper and wrap it around the beaker and hold it tightly at the end (to make sure I don’t find it too hot and let go of it).
Detailed method: The temperatures I am going to use are 20, 30, 40, 50, and 60oC. I will use this range because it seems like a good temperature to use and I will get a wide variation of results. I have started with 20oC because that near room temperature. I will need to get an average of a few results of the same temperature, to get meaningful results. I am going to use 5ml of Hydrochloric acid and 10ml of Sodium Thiosulphate. I will make accurate measurements. I will do this by using the right measuring cylinder (To measure 10ml of Sodium Thiosulphate and 5ml of Hydrochloric acid I will use 10ml measuring cylinders, to measure 40ml of distilled water I will use a 100ml measuring cylinder). To keep it a fair test I will use the same measurements for the temperature and substances (Sodium Thiosulphate, Hydrochloric acid ; distilled water).