FLOTATION

1. Let’s Get Physical: FLOTATION

2. AIM • Flotation: A piece of a flattened raisin, which is dropped into a glass of soda water, periodically sinks and goes back to the surface. Investigate the dependence of the period of these oscillations on various parameters. (Note: a combination of vinegar and bicarb of soda in water also works quite well).

3. KEY CONCEPTS • Why does the raisin sink then float? • Higher density ∴ sinks • CO2 provides less dense medium ∴ floats • Bubbles pop, CO2 escapes so back to top

4. KEY VARIABLES • Surface area of sultana • Kept constant (uncertain uncertainty) • Weight of sultana • Kept constant (uncertainty: 9.2%) • Size of sultana • Kept constant (uncertain uncertainty) • Amount of CO2 being released • Varied

5. MATERIALS • 1x Glass Tube • 2x 250 mL beakers • 5x sultanas • 500 mL white vinegar • 20.37g baking (bicarbonate) soda • 1x 600g scale

6. METHOD • 100 mLvinegar poured into tube • Soda measured out • Tube of vinegar placed on scale, weighed • Soda added • Waited 20s • Sultana added • Oscillations counted over 120s, final weight taken at end

7. METHOD

8. METHOD

9. SAFETY • Lab coat & goggles optional • Basic lab rules – no running, etc. • Glassware involved • Add bicarb gradually • Prevents liquid getting on to electronic equipment

10. DIFFICULTIES • Surface area of sultana • Kept constant (uncertain uncertainty) • Weight of sultana • Kept constant (uncertainty: 9.2%) • 0.46g ± 0.05g (avg ± st dev) • Size of sultana • Kept constant • (uncertainty)

11. RESULTS

12. ANALYSIS

13. ANALYSIS Frequency = Oscillations / second Frequency = Period =

14. CONCLUSION • Gas being released increases • Oscillations increase exponentially • Period decreases inversely • Many minute variables • Requires precise instruments