See how long it takes for sodium Thiosulphate and hydrochloric acid to react at different concentrations.

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Disappearing cross investigation

Aim:

To see how long it takes for sodium Thiosulphate and hydrochloric acid to react at different concentrations.

My Hypothesis:

Using the idea of the particle theory, the more dilute a solution is, the more time it will take for the particles to react. This is due to the fact that the particles have less energy reducing the collisions and the speed of which they collide, therefore taking longer to react. I predict that the more water I add to the solution the longer it will take the cross to not be visible.

Variables:

In this experiment I will only need to decrease the concentration of the Thiosulphate and I will need to increase the concentration of the water. All of the other factors I shall keep the same.  To keep the experiment in a fair I will make sure that all the measurements that I take are as accurate as possible. I will also make sure that all the timing is exact. I will stir the each solution for the same amount of time each time so that it is fair.

        There are a few factors that will effect how the experiment works.  You have to make sure that the sodium thiosulphate does not mix with any water before the experiment this can make the experiment inaccurate and can ruin the results because of cross contamination. I have to be careful not to stir a experiment longer than the other because the more you stir the solution, the more it will speed up the experiment. I will control the variables by using different measuring cylinders for each substance so there is no cross contamination.

        It is important that I control the variables because if I don’t it could make the test unfair. If the sodium thiosulphate solution mixes with water before the experiment it will become more dilute therefore it will take longer for the solution to react.

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My aim is to calculate the time it takes for the cross to disappear for each measurement.  I will write down the time as soon as I see the cross disappear. I will do each experiment three times and I will take the average for each.  I shall do this to make sure the results are as accurate as possible in case one of the experiments we miss calculated and to prevent any bad results.

Measurements:

In this experiment I am going to measure the time it takes for the cross to disappear from my view. ...

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