Introduction: In the investigation I will see how long it takes for sodium thiosulfate to react with hydrochloric acid, sodium thiosulfate will be diluted with water, I will do it having 60 ml of sodium thiosulphate and 40 ml of water but each time I will change the amount of sodium thiosulphate and water but the sum of both will result in 100 ml, I will know when the reaction has taken place because the glass with the chemicals at inside will become cloudy, we will put the glass on a piece of paper with an ax on it. When the glass becomes cloudy, the x will disappear and that's when I will stop time and record my results on a table, I will repeat this every time I perform the experiment. Collision theory: particles can only react if they collide with enough energy for a reaction, this is called collision theory there are four factors that can change the rate of a chemical reaction between particles: temperature, energy, surface area and l use of an adequate concentration. By increasing the temperature the particles will move faster and with more energy which will speed up the reaction because the particles will collide more often. Increasing the concentration of the reactant means that there are more particles in the reaction and therefore there will be more collisions. Using a powder instead of a solid means the concentration is higher, meaning there is a larger reaction area so the particles can move faster. Word equations: Na2 So3 + 2HCI = 2Na C1 + H2O + So2 +SSodium thiosulfate + hydrochloric acid = sodium chloride + water + sulfur dioxide + sulfur Equipment: Beakers: P...... center of paper ... ...r for the solution to become cloudy. I could have improved my experiment by running all the tests on the same day, this would help the test to be more correct since the room temperature would be the same and would not alter the results of the experiment. I could also have, instead of using a piece of paper with an ax on it, used a single ray of light to pass through the solution and then when the glass had clouded I would no longer be able to see the light, I could also have put a light sensor above the glass so that when the light stops passing through the solution it automatically stops the stopwatch. This would cause my test to become more accurate as soon as the light stopped passing through, time would stop without delay, but if I did it manually a small amount of time would elapse before the stopwatch could be stopped.