When two or more molecules interact there is a reaction which causes the molecules to change. To make new molecules, the bonds between atoms are broken and created to make them.
When the products change and reactant this is called Rate of reaction. Many factors contribute to rate of reaction being affected. For example, the nature of the reactants, the particle size of the reactants, the concentration of the reactants, the pressure of gaseous reactants, the temperature and finally the catalysts.
The hypo solution that was put in the flask was the controlled variable and the same amount was used throughout experiment. The temperature of the water is the independent variable, each time the experiment was done the water was changed. The dependent variable is 25ml of hydrochloric acid and 100ml of water in the flask.
Aim: The aim is to determine the connection between the reaction, the changing in temperature and the concentration.
25mL Hypo (0.2M sodium thiosulfate Na2S2O3 )
2.4 mL 1M Hydrochloric acid (HCl)
Water (hot, cold and room temperature)
1. Measure out 25ml of hypo solution in a 100ml flask.
2. Find the temperature and record it as room temperature.
3. Mark a cross/x in pen on a blank sheet of white paper and place the flask on top of the cross.
4. Add 5ml of hydrochloric acid to the flask. Since the chemical reaction is taking place, the solution will go a non-transparent yellow colour. The cross will seem to disappear when looked at the flask from a bird’s eye view.
5. Measure the time from when the acid is added and when the cross beneath the flask disappears.
6. Clean flask.
7. Repeat step one
8. Put water in an empty 2L ice-cream container with ice.
9. Put the flask with the hypo in it in the container of icy water and let cool to 10 degrees Celsius.
10. When cooled, quickly remove flask out of the ice, wipe the water from the outside and put the flask ontop of the cross.
11. Repeat step 4
12. Repeat step 6
13. Repeat step 1
14. Empty the container
15. Put hot water in the container.
16. Sit the flask in the container and let the temperature get to 40 degrees Celsius.
17. Take the flask out of the hot water and put the flask over the cross.
18. Repeat step 4