Let’s Get Physical:

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).

KEY CONCEPTS  Why does the raisin sink then float? Higher density ∴ sinks CO 2 provides less dense medium ∴ floats Bubbles pop, CO 2 escapes so back to top

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 CO 2 being released Varied

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

METHOD 1) 100 mL vinegar poured into tube 2) Soda measured out 3) Tube of vinegar placed on scale, weighed 4) Soda added 5) Waited 20s 6) Sultana added 7) Oscillations counted over 120s, final weight taken at end

METHOD

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

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)

RESULTS Weight of Sultana (g) Amount of Bicarb (g) Vinegar (mL) 100 Weight of Vinegar + Tube (g) Final Weight (g) # of Oscillations 92486

ANALYSIS Weight of Sultana (g) Amount of Bicarb (g) Vinegar (mL) 100 Weight of Vinegar + Tube (g) Calculated Start Weight (g) Final Weight (g) Calculated Gas Released (g) # of Oscillations Calculated Period (s)

ANALYSIS

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