Disappearing Cross Investigation

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.

My aim is to calculate the time it takes for the cross to disappear