1. Science Quiz Teeth test By F. 4E

2. Group List Leung Chi Heng Cheung Long Hang Ho Yik Ki Chan Kan Hei

3. Content P.1 Purpose P.2 Hypothesis P.3-4 Experiment design P.5 Apparatus P.6 Materials P.7-8 Procedures P.9-12 Results P.13 assumption P.14-15 conclusion P.16 Error

4. Purpose To determine whether toothpaste can protect teeth from decaying ; And which toothpaste can protect teeth better.

5. Hypothesis Our first hypothesis was that all toothpastes can protect teeth from decaying. Our second hypothesis was that Colgate toothpaste could protect teeth from decaying most effectively.

6. Experiment design (1) The constants in this study were: 1. Number of egg(1 egg) 2. Type of egg 3. Type of acids (hydrochloric and carbonic acid) 4. Concentration of acids 5. Quantity of acid (40mL) 6. Quantity of toothpaste 7. Amount of time to keep the teeth in acid (20 hours)

7. Experiment design (2) The manipulated variables: 1. Presence of toothpaste 2. Type of toothpaste (Lion, Colgate, Darlie and Oral B ) Responding variables: 1. The appearance of the tested eggs surface 2. The mass of the tested egg

8. Apparatus Quantity10411 ItemBeakers (100mL size) Beakers (?00mL size) Electrical balance Hair Dryer Quantity4141 ItemBunsen burners Dry towelSafety glasses Pile of label paper Quantity4411 ItemTripodHeat-proof mat StarterCamera

9. Materials Quantity (M)10 ItemEggsOral B toothpaste Lion( ) toothpaste Darlie( ) toothpaste Quantity (M)200mL1 (200mL) ItemColgate Toothpaste Dilute hydrochloric acid (2M) Coca-cola (carbonic acid)

10. Procedures (1) 1. Boil the eggs. 2. Dry the eggs with a hair dryer and a dry towel. 3. Label the beakers with label paper (A1, A2, B1, …, D2) 4. Mark down their appearance by taking photos. 5. Measure the mass of eggs by the electrical balance. 6. Put a thin layer of toothpaste on the eggs 7. Put the eggs in beakers.

11. Procedures (2) 8. Pour 40ml of hydrochloric acid on each of them. 9. Repeat step 8 except using coca-cola (carbonic acid). Keep it in acid for 20 hours 10. Wash away the toothpaste. 11. Dry it up. 12. Mark down their appearance by taking photos. 13. Measure the mass of the eggs. 14. Calculate the %change of mass of the eggs. * Control: Repeat steps 1-14 without adding toothpaste

12. Results The result of this experiment were: (With HCl) All the toothpaste we tested, reduced the mass losses of the eggs,comparing with that of the egg without toothpaste. Overall, mass loss of egg with Lion toothpaste was the least, then Colgate, and then Oral B, the most was Darlie.

13. Results 2 Actually,we have also used coke to test the eggs. But it failed as we found the mass of the eggs are heavier than it was! We think that this may be caused by the absorption of coke, as the coke contains other substances

14. Result comparing

15. Appearance change Beforeafter

16. Assumption The higher degree of reducing mass loss,the higher efficiency of protecting teeth.

17. Conclusion Our first hypothesis was that all toothpastes can protect teeth from decaying. The results indicate that this hypothesis should be accepted. Our second hypothesis was that Colgate toothpaste would be the most effective at protecting teeth. The results indicate that this hypothesis should be rejected. According to our result,Lion toothpaste can protect teeth better than Colgate toothpaste.

18. Source of Error The surface areas of the eggs are not equal. The distribution of toothpaste on the eggs may not be even. The eggs may absorb the acids which cause an increase in mass.

19. Special Thanks Mr Yu. Mr Lee,the chem. lab technician. Mr Andy.Tse. Science society.

20. The End Thank you for your attention!