Flotation

Liam King, Arthur Kyriakopoulos, Vincent Lu (MSC)

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).

Aim• The aim of this experiment was to

understand why raisins oscillated in soda water.

• And if so, what the correlation between the period of oscillation and mass of the raisin is.

Hypothesis• The more mass a raisin has, the less it will

oscillate in the water.

What is actually happening?• Bubbles are produced and this causes the raisin to

oscillate.• When the raisins are put in the water and vinegar they

sink.• The bubbles cause the raisins to rise.• This means that the density of the sultanas change as

they are made less dense by external gas bubbles.

Variables ● Period of oscillation (Dependent)● Mass of raisin (independent)● Surface area of raisin (control)● Temperature of room (control)● How the raisin was dried and treated (control)● Fizziness of soda water (control)● Width of beaker (control)● Volume of liquid (control)● Temperature of water (control)● Oscillation height (5cm) (control)

Theory• A raisin will oscillate due to carbon dioxide

bubbles getting caught in the ridges in the raisins.

• Once the bubbles pop (being exposed to air), the raisins will return to the bottom of the beaker.

Materials • Water

• Vinegar

• Bicarb soda

• Raisins

• Scale

• Spoon

• Beaker

• Stopwatch

Method• Mix water (100ml) and vinegar (150ml) in a beaker.• Add bicarb soda (5g) to the beaker.• Add one raisin.• Use a stopwatch to measure the length of time

between each oscillation of the raisin (how long it takes to get to the top and how long it takes to get to the bottom of the beaker).

ResultsRaisin 1,3,4,9

Surface area (mm) 5*5*5

Volume of raisin (mL^3) 0.2

Results Raisin 1Mass (212 grams)

Period of movement Time (seconds)

1 6.142 5.283 2.564 1.355 10.286 8.17 35.438 3.419 8.3510 0.89

Odd number indicates a movement up and even numbers indicate a movement down from the raisin.

Results Raisin 3Mass (205 grams)

Period of movement Time (seconds)

1 4.082 2.933 3.594 1.965 3.486 8.417 4.918 9.29 4.7310 3.61

Odd number indicates a movement up and even numbers indicate a movement down from the raisin.

Results Raisin 4Mass (242 grams)

Period of movement Time (seconds)

1 6.422 1.223 2.994 7.065 266 3.857

8

9

10

Odd number indicates a movement up and even numbers indicate a movement down from the raisin.

Results Raisin 9Mass (250 grams)

Period of movement Time (seconds)

1 2.582 2.513 3.594 0.945 1.96 1.437

8

9

10

Odd number indicates a movement up and even numbers indicate a movement down from the raisin.

Results

Conclusion• The hypothesis was supported that raisins

with a greater mass will oscillate less. This is shown from our results as raisin 3 with the smallest mass oscillated the most and raisin 9 with the greatest mass oscillated the least.