Session 5: Pressure and Density

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Objectives 1:  With this experiment students will observe  that the pressure varies depending of the density of the liquid.

 

Explanation:

Material:

• Transparent container
• Soda plastic bottles with three different diameters
• Or Plexiglas tubes with 3 different diameters
• Take a piece of rigid material, that resists water, light plastic for example
• Fluid: Glycerol, Oil
• Scale
• Reference volume 100 ml

Maximum duration:

45 minutes

Main question to be asked:

Introduction/Starters

Ask the kids to put their hand in a hermetic plastic bag and again feel the pressure of water. Then take a fluid with very high density and ask them to repeat the experiments.

What do they feel?

Main activities

A. Density of the fluids

• Give them the 3 types of liquid: oil, water and glycerol and ask them to comment on these liquids.
• Normally the aspect of weight will come out. Ask them how to compare these fluids in terms of weight.
• Propose them to weigh a given volume for each fluid.
• At this stage we will repeat the experiments of session 4, replacing the water by the fluids which are respectively more and less dense than the water.

B.Test the parameter of fluid density

• Close the bottom of the middle size tube with a piece of light rigid plastic.
• Push the piece of plastic firmly and then dip the tube within your container of water halfway up. If you did well the pressure should ensure the seal and the water does not enter the plexiglass tube
• Question to ask your student: how much fluid less dense than water you will add before the piece of plastic will be released?
• Do the same experiments, and stop filling with the water just before the release of the piece of plastic. Then push your tube lower within the water. What do you have to do to release the plastic?
• Conclude with the students, as the height of water increases the pressure…

Conclusion/Plenary