Pressure in fluids
These hand-picked practical activities explore pressure and particle theory for students aged 11-14, with tips and advice for non-physicists.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
Machines 11-14
This whole suite of materials is good, but of particular relevance to this topic are the first three activities in the second unit; What’s in Pressure?
Having “played” with a tray of marbles in the first activity, students should develop quite a sophisticated understanding of pressure at a particulate level. They then go on to apply their ideas, thinking about the relationship between pressure, force and area before feeling the forces for themselves with a pair of syringes. Teachers will be able to assess student’s understanding of this topic by asking them to draw diagrams showing the moving particles inside the syringes.
Demonstrating Physics: Forces
There are a couple of demonstrations included on this film which fit snugly into this topic.
Expanding Marshmallows starts about 3½ min into the film and shows how the air trapped inside marshmallows will expand significantly if the air pressure outside is reduced, it’s a great demonstration.
It is also an experiment that can be carried out quickly and easily by students using small marshmallows (the type used on top of hot drinks) and 10 or 20cm3 plastic syringes.
1. After removing the plunger, put the marshmallow into the syringe
2. Replace the plunger and gently push it up until it is just below the marshmallow
3. Putting the finger over the open end of the syringe, pull down on the plunger whilst observing the marshmallow expand
4. The marshmallow shrinks rapidly when the finger is removed
5. Similarly, using the plunger to compress a syringe full of air will shrink the marshmallow and it will now expand when the finger is removed.
The Cartesian Diver starts about 8½ min into the film and it excellent for showing the effect of pressure in liquids. It’s good to demonstrate it with a test tube inside a two litre bottle so that students can see the air bubble changing size. Once they've seen this they could carry out the experiment for themselves, perhaps using sauce sachets which are easier to handle than the tubes.
Physics for Non-Physicists: Forces
In this video a group of physics non-specialists are offered help on how to approach the teaching of forces. The introduction to forces starts with a bazooka: a homemade, partially evacuated tube which fires missiles at a target. Then they are introduced to a bubble investigation where air bubbles are released in glycerol and rise up a small container. One of the teachers tries this investigation with a year seven group. Which bubble will reach the top first?
The Cartesian Diver
A short video aimed at supporting teachers with student lead investigations. In this particular clip students investigate a Cartesian diver and how the teacher's 'magic trick' works.
Demonstrating Physics: Electrostatics
In this Demonstrating Physics video clip a biology specialist is supported to use a Van de Graaff Generator. This teacher then demonstrates the experiment to a class of year eleven students.
Atmospheric pressure
This series of videos gradually build on the concepts that lead to an understanding of air pressure an contain clips of some interesting demonstrations to show its effects which could be replicated in a classroom.