Learning objectives
iLiquids cannot be squashed because there is no space between the particles.
iiPressure in a liquid acts equally and in all directions.
iiiA hydraulic machine uses a small force on a small input piston to produce a much larger force on a larger output piston connected to it.
ivWater has its own pressure. The deeper you go, the heavier the weight of water so water pressure increases.
Scientific enquiry
vPredict the behaviour of water under pressure. (Framework YTO Sc1 9f)
Suggested alternative starter activities (5–10 minutes)
Recap last lesson / Share learning objectives / Problem solving / Brainstorming / Capture interest
Each group has a potato trimmed to give a flat base and nine identical drawing pins. They try to balance the potato on nine pins and then on one pin, without the pins sticking in the potato. /
  • Describe how pressure affects liquids.
  • Explain how hydraulic machines work.
  • Predict the behaviour of water under pressure. (Sc1)
/ Decide if each of a set of descriptions is of a liquid or a gas. / Show pupils a balloon blown up with air. Ask them to imagine what will happen as a diver holds the string and swims down to the ocean floor with it. / Show photos/video clips of any hydraulic systems.
Catalyst Interactive Presentations 3
Suggested alternative main activities
Activity / Learning objectives see above / Description / Approx.
timing / Target group
C / H / E / S
Textbook L2 / i, ii, iii, iv and v / Teacher-led explanation and questioning OR Pupils work individually, in pairs or in small groups through the in-text questions and then onto the end-of-spread questions if time allows. / 20 min / R/G / G / R / S
Activity L2a Practical / ii, iv and v / Pressure in liquidsDemonstration to show pupils that the pressure in a liquid increases with depth and is equal in all directions, and because of this the surface of a liquid is always level. / 20 min / 
Activity L2b Practical / i, iii and v / HydraulicsPupils use syringes to investigate the principles of hydraulics. (The Help sheet is a demonstration.) / 30 min /  /  / 
Activity L2c Paper / ii, iii and v / Squeezing liquidsPupils practise calculations involving hydraulic systems. / 15 min / 
Activity L2d
Catalyst Interactive Presentations 3 / i, ii and iii / Some animated pistons reinforce the idea that the small piston moves a long way and pushes the large piston out a short way. Also reinforces the idea that with the hydraulic system force can be transferred round corners. / 5–10 min / 
Suggested alternative plenary activities (5–10 minutes)
Review learning / Sharing responses / Group feedback / Brainstorming / Looking ahead
Demonstrate a model of a hydraulic system (e.g. syringe model, or pump model). / Pupils work in groups to produce true or false answers to questions about pressure in liquids as a follow-up to Activity L2a. / Each group summarises what they found out about hydraulics in Activity L2b and explains to the class. / Pupils look at a diagram of the Peterborough Hydraulic Lift Lock in Canada and order a series of statements about how it works. / Pupils use syringes to see whether air can be compressed.
Learning outcomes
Most pupils will … / Some pupils, making less progress will … / Some pupils, making more progress will …
  • use the relationship between force, area and pressure within liquids
  • apply the particle model of matter to explain why liquids are incompressible
  • use the concept of transmission of pressure to predict resultant forces
  • identify some everyday effects of water pressure.
/
  • know that pressure acts equally and in all directions in liquids because the particles can′t be squashed.
/
  • use the definition of pressure in calculations to explain the operation of a range of devices.

Key words / Out-of-lesson learning
hydraulic machine, cylinder, piston, water pressure, red only:transmit, magnify / Homework L2
Textbook L2 end-of-spread questions
Activity L2c
Watch a hydraulic jack in operation – write a description of how it works for a catalogue

© Harcourt Education Ltd 2004 Catalyst 3

This worksheet may have been altered from the original on the CD-ROM.