Experiment: Can Temperature Change the Reaction Time of Something?

A thermometer (to measure the temperature at which the reaction will take place),

A piece of paper (to draw a cross on),

A black pen (to draw a cross),

A measuring cylinder to measure how much of each substance I will use.

(FIGURE 1)

Showing the equipment set up ready for the experiment.

METHOD;

Before you start an experiment you need a plan to work from. The plan (below) includes the order I will do each part of the experiment in,

1. Collect the equipment for the experiment using the list above,
2. Set up the equipment as shown in figure 1,
3. Find a person to help me in the experiment,
4. Draw a black cross on a piece of paper using 5 cm lines,
5. Put some hydrochloric acid (5 ml) in the glass conical and thiosulphate (5 ml) in another,
6. Heat the hydrochloric acid and thiosulphate in different conical until they are at the given temperature,
7. When you mix the hydrochloric acid with the thiosulphate (in one of the conical on the black cross) you must start the stop watch as soon as they touch,
8. Record the time taken for the cross to disappear and repeat the experiment for about 5 different temperatures and making sure that the hydrochloric acid is at the same temperature each experiment,

VARIABLES:

In this experiment there are a number of things I could change. These are:

• The temperature
• The amount of each substance
• The size of the cross
• The colour of the cross
• Adding a catalyst
• Stirring the mixture
• The concentration of each substance

I have chosen to change the temperature of the thiosulphate for my experiment, I cannot heat the hydrochloric acid because it would give off a harmful gas. This means that I will have to keep the following the same for each experiment:

• The amount of each substance
• The size of the cross
• The colour of the cross
• No catalysts
• Stirring the mixture
• The concentration of each substance

PREDICTION:

I think that when the Bunsen flame is more violent and therefore the temperature is higher then the reaction will take place much faster. This is because the particles reacting will have more energy because of the heat and therefore will bump into each other more. When the temperature isn't so great then the particles of thiosulphate and hydrochloric acid will not have so much energy and so will therefore bump into each other less.

MEASUREMENTS:

In this experiment I shall be taking five tests at different temperatures but will then do the test for each temperature three times and take the average.

EXTRA KNOWLEDGE:

What is the most accurate way of obtaining the reaction rate between sodium thiosulphate and hydrochloric acid?

Reaction, over a certain time, is equal to the change in concentration of the reactant or the product divided by the time taken. Which method you use depends on the type of reaction it is. One way of finding this out is by carrying the reaction out in a thermostatically controlled bath - i.e. one that you can control the temperature of. A sample of the reacting mixture is withdrawn with a pipette and the reaction within this bit of the mixture is stopped. This can be done in a number of ways like removing one of the reagents or suddenly cooling the mixture. You then perform a titration to find the concentration of one of the reactants or one of the products. If you do this at regular intervals you can determine the rate at which the reaction is happening. In a reaction where a gas is formed you have to use a different method. The volume of gas must be recorded at various times.

OBTAINING EVIDENCE

IMPROVEMENTS:

I have found that the reactions take too long so I am now using 20 ml of each of the chemicals.

TABLE OF RESULTS

GRAPHS

(See Graphs on following page)

PATTERNS AND TRENDS:

From the results I can see that as you raise the temperature the reaction time decreases.

CONCLUSION;

I now know that my prediction was correct. When the Bunsen flame is more violent and therefore the temperature is higher then the reaction takes place much faster. This is because the particles reacting have more energy and therefore bump into each other more. When the temperature isn't so great then the particles of thiosulphate and hydrochloric acid do not have so much energy and so, therefore, bump into each other less. This is because the particles reacting will have more energy because of the heat and therefore will bump into each other more. When the temperature isn't so great then the particles of thiosulphate and hydrochloric acid will not have so much energy and so will therefore bump into each other less.

The graph also shows you this because the line increases in height as the temperature becomes greater.

EVALUATION:

I think that the results were fairly accurate though the test were definitely as fair as they could get, there are a few things that could make the results a little more accurate. These things are the fact that you are using your eyes to determine when the test is finished. To over come this you could use a light sensory kit that would stop the experiment at a certain point when the cross disappears. Another thing wrong with the experiment is that it is extremely hard to get the temperature just right and then to keep the temperature the same whilst the reaction is taking place is impossible. There is one way you could possible get around this, you could use something like a water bath that could keep the temperature of the reaction the same until it has finished.

The method of the experiment wasn't bad and it worked so I guess it was quite good. In the experiment there was one thing I had to change though and that was to add more of each of the substances, Thiosulphate and Hydrochloric Acid, to the reaction as the experiment wasn't taking place fast enough. Otherwise I would have been stood there for hours and I also would have been hard to see a reaction taking place as the cross disappears.

Other than these factors then we could say that the experiment went successfully and I received some quite accurate results.