The underwater drop

Materials:

1. A small container and a big glass.
2. Oil
3. Water
4. Alcohol
5. Glue and coin.
6. A spoon.

If the container is made of plastic, we stick a coin at its base in order to get more stability and avoid floating.

We fill the half a container with oil.
We put it at the bottom of the glass.
We pour the alcohol necessary to cover the container very carefully.

Then, we add water little by little with a spoon (it must slip from the wall of the glass).
Small container's surface filled with oil will adopt a convex shape until the water you add is enough. Then, the oil will separate from this container and it will have a spherical form that will remain just in the middle inside the oil and water mixture.

EXPLANATION:
First, we must know the densities of the liquids we use in the experiment.
- water (1g/ml)
- oil (0'92 g/ml)
- Alcohol (0'75 g/ml)

The oil floats in the water because it's less dense than water, but it sinks into alcohol because it's denser than it. In conclusion, you can prepare a mixture with alcohol and water because inside it, oil won’t float or sink.

by Ana, Marta and Belén

OIL POMP

Materials:
1 One small container and one larger glass
2 Oil
3 Water
4 Glue and one coin
5 Spoon
6 Alcohol

Assembly:
1. If the container is of plastic we put on the base one coin to give it stability and to avoid that it floats.
2. You take the small container, and you fill the container until the middle with oil and you see that the oil sets on the bottom of the glass.
3 Inside the glass you fill with precaution, the amount of alcohol that you need to cover the small container. Then with a spoon, you add, little by little, water.The surface of the oil from the small container will be more and more convex, when the water that you have added is the necessary, the oil will give off the container and will forma sphere that will be floating inside the mixture of water and alcohol.

Explanation:
The densities of the three liquids : water (1g/ml), oil (0,92g/ml) and alcohol (0,79g/ml).
The oil floats on the water because it is less dense than the water, but the oil doesn’t float on the alcohol because it is denser. So you can prepare one mixture of water an alcohol, where this oil won’t float and won’t sink until the bottom.

by Macarena, Irene and Sofía