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7.10Physics 01. Forces And Energy

Use particle theory to explain pressures in gases and liquids… — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions

5 min read 8 parts Lesson 11 of 12 1 quiz

📚 Cambridge Checkpoint Science 0893 Hub / Topical Revision
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Lesson summary

7.10 Pressure in solids, liquids and gases explained with particle theory — CHECKPOINT - Lower Secondary Science 0893 notes: Use particle theory to explain pressure in gases and liquids, and relate pressure to force and area.Pressure — the pushing effect of a force on an area.Equ…

  • Larger force
  • Smaller area
  • Small area examples
  • Large area examples
  • Applications
  • More particles

Section 1 of 8Pressure

Pressure
  • Pressure the pushing effect of a force on an area.
Equation
  • Equation pressure = force ÷ area
  • Force is in newtons and area is in square metres, so pressure is in N/m2.
  • If the area is in cm2 the unit is N/cm2.

Section 2 of 8Changing pressure on solids

Larger force
  • Larger force it gives a larger pressure.
Smaller area
  • Smaller area it gives a larger pressure.
Small area examples
  • Small area examples nails, pins and knives have sharp points or edges to increase pressure.
Large area examples
  • Large area examples camel feet and snow shoes spread the weight to decrease pressure.

Section 3 of 8Pressure in liquids

Pressure in liquids
Particles
  • Particles they move randomly in all directions and collide with the container walls.
Depth
  • Depth the pressure in a liquid increases with depth.
  • More liquid above a position means more weight pushing on the particles.
  • The particles move with more force.
Direction
  • Direction the pressure acts equally in all directions at the same depth.
Applications
  • Applications a dam wall is thicker at the bottom and submarines must be strong.

Section 4 of 8Pressure in gases

Pressure in gases
Cause
  • Cause gas particles move randomly and collide with the walls of their container.
  • Each collision exerts a small force on the wall.
  • The force acting on an area gives pressure.
More particles
  • More particles more collisions per second and a higher pressure.
Higher temperature
  • Higher temperature particles move faster and collide with more force, so the pressure rises.
Example
  • Example a sealed pressure cooker has a high pressure because of the hot steam.

Section 5 of 8Atmospheric pressure

Atmosphere
  • Atmosphere the layer of gases around the Earth.
Highest at sea level
  • Highest at sea level the atmosphere is deepest at sea level and there is most weight of air above.
Altitude
  • Altitude higher up, there are fewer particles in a volume and less weight of air above, so the pressure falls.
Evidence
  • Evidence pumping air out of a metal can makes outside pressure crush it, because the inside pressure falls close to zero.

Section 6 of 8Effects of changes on a gas

ChangeEffect on pressureReason
Add more gas to the same containerHigherMore collisions
Heat the gasHigherFaster particles collide harder
Cool the gasLowerSlower particles collide less
Remove all the gasZeroNo particles to collide

Section 7 of 8Key terms

TermMeaning
PressureForce acting on a unit area.
Atmospheric pressurePressure caused by the weight of the air above.
DepthDistance below the surface of a liquid.
CollisionParticles hitting each other or a wall.
AltitudeHeight above sea level.

Section 8 of 8Exam technique

1
Pressure in a liquid acts only downwards — it acts equally in all directions at the same depth.
2
Gas pressure is caused by the weight of the gas particles — it is caused by collisions with the walls.
3
Pressure and force are the same — pressure is force divided by area.
4
Pressure does not change with height in the atmosphere — it decreases with altitude.

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