Hydrochloric acid and thiosulphate are both clear liquids. They react to make sulphar, which if inhaled, can be harmfal. When te experiemtn takes place get rid of the mixture as soon as it goes cloudy. A cross must be drawn and the conical flask put on top. The higher the concentration of thiosulphate the quiker the reaction becuase there are more particles to react.
The different concentrations of thiosulphate must be poored separetly into the conical flask containing 15cm3 of hydrochloric acid. When the mixture goes cloudy the raction stops. A stop watch should be used to time how long the reaction takes.
On average it takes about 1 minute when the concentration is 50:50 and whewn 10:40 it takes 7 minutes. This shows that the higher the concentration the quiker the amount of sulphar is produced.
Varying the temperature can also effect the amount of sulphar that is prduced.
The line of best fir would be curved showing that the higher the temperature the quiker the reaction.
To make a fair test: keep the same concentration of water, sodium thiosulphate and hydrochlric acid.