Group 4 Project

Group 5: Beatrice, May, Pena, Phuntsok.

Buoyancy in sea and lake water and the factors affecting it.

• We decided to investigate on the different buoyancy in Devon’s sea and Ley.

• Our hypothesis: Buoyancy in sea water is greater than that of the Ley’s water as salty water is more dense than fresh water.

• Aim: Prove that our hypothesis is right and explain.

Equipment used

• 1 cylinder (500ml)• 1 magnifying glass• 1 tray• 1 kick sampling net• 1 microscope • 1 mass• 1 crucible • 4 vials• 1 microwave• Weighing scale• 2 petridishes

First Steps

• This morning we went over the final plans of the day. • When we went to get our equipment we faced our

first problem: the center didn’t have a Newton meter, an essential equipment to measure Buoyancy.

Solution: with the help of Dr Adedapo and Mr Beardsell we found an alternative that consisted of using a mass(vial with stones in) and taking note of how deep it sunk into the water (contained in a 500ml cylinder).

Explaining our hypothesis: Chemistry experiment

• Why is salty water denser that fresh water?

• Method: -Take 2 crucibles and measure their weight without anything in them.-Weight of the bowls with 5 ml ³ of each type of water.-Put the bowls and heat in a microwave until all the water evaporates.-Measure the weight of the bowls.

Chemistry ResultsVariable Weight in fresh water Weight in sea water

Weight of crucibles without water

19 g 19 g

Weight crucibles with 5 ml³ 24 g 23 g

Weight of crucibles 19 g 19.6 g

Conclusion:We can conclude that there is more salt in sea water then in the Ley’s water, therefore, there is more buoyancy in sea water.

Buoyancy experiment : Physics

Method:We went to the Ley and Sea and sample 1L of water in

separate bottles and brought them back to the lab.

Variables:Dependent – Ley and Sea waterIndependent – BuoyancyControlled – 500 ml cylinder, mass

Diagram: Physics Experiment

320 ml

440ml

340ml

Sample of Ley water in a cylinder with a mass that floats at 320 ml

440ml

330ml

310ml

Sample of sea water in a cylinder with a mass that floats at 310 ml

cylinder

mass

Results of physics experiment and conclusion

Our hypothesis is not correct as a matter of fact the experiment proves that a mass floats higher in sea water than that of the Ley’s water.

As we were proven wrong, we came to ask ourselves: Is the Ley’s water pure fresh water?

This led to another series of experiments.

EVS Experiment: Organisms in different water environment

• We used the method of kick sampling to discover the organisms living in the two different water bodies. To indentify the organisms we used a Key provided by the centre. In each case the same amount of water ( 1L) was sampled. The density of organisms found determine the amount of pollution contained in the water. Pollution is more particles, and would make the mass float more.

Sample of fresh water in a tray

Sample of sea water in a tray

EVS Experiment results

Ley:•2 Biting midge Larva•Over 15 non biting midge larva•8 fresh water shrimp•1 swimming Mayfly Nymph•1 Demoiselle Damselfly

Sea:•1 sea water shrimp carrying a baby

We can see that the Ley is much more rich in organisms. It presents a varied amount of species of invertebrates. But on the other side the sea has a fertile environment (as we identified a baby shrimp).

Biology Experiment

• See Poster

Proof • To prove that all of the organisms in the Ley’s water were the ones

impacting the density of the water and therefore the Buoyancy we redid the first Physics experiment with fresh tap water.

300 ml

320 ml

Sample of fresh tap water in a cylinder with a mass that floats at 300 ml

440ml

Conclusion and Evaluation

• Ley’s water buoyancy is in fact greater than salt water due to the higher density of living microscopic organisms that we identified in our samples.

• Because we were wrong with our first hypothesis, which we thought would lead to the greater buoyancy in salt water, we changed our scope to the factors that were causing the greater buoyancy in Ley’s lake water.