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Pressure and the Particle Model

In this worksheet, students learn about the concept of pressure in all states of matter in relation to the Particle Model.

'Pressure and the Particle Model' worksheet

Key stage:  KS 4

Curriculum topic:  Physics: The Structure of Matter

Curriculum subtopic:  Relating Models of Arrangements and Motions of Molecules

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

Think what would happen if you were to push a pin on its pointy end against a wall. Yes, you would hurt yourself. However, the pin would be inserted into the wall if you pushed it on its flat end.

 

Assuming you applied the same force in both cases, the end result would be different, because of the difference in the pressure applied on your thumb. In the first case, the force is concentrated on a very small area, so the pressure is very high. In the second, the force is spread out over a larger area, so the pressure is lower.

 

The formula used to calculate pressure is:

 

pressure = force / area

 

When the force is in Newton (N) and the area in m2, the unit for pressure is Pascal (Pa) or N/m2. If the area is in cm2, then the pressure is measured in N/cm2.

 

In liquids, pressure increases with depth. It is very dangerous to dive very deep into the sea, because water pressure will crush your body. The same can happen even to a submarine if it goes down to depths where its structure cannot support it against water pressure. Usually, taps downstairs run faster than ones upstairs and dam walls have to be thicker at the bottom. This is because water pressure gets higher as you go further below the surface of water.

Pressure is transmitted through liquids, because they are incompressible. This means they cannot be squashed. This property is taken advantage of in hydraulic systems. A good example of hydraulics is the car brake system. The pressure of the fluid is the same throughout, so the surface area of the cylinders is adjusted accordingly. Gases are compressible (they can be squashed), but gas particles still exert pressure. Atmospheric pressure at the surface of the Earth is 100,000 Pa. Our bodies have evolved to withstand this pressure. The higher the altitude, the fewer the air particles, so the smaller the pressure. Pressure in gases is caused by collisions of the particles.

Use your imagination to visualise how gas particles collide (crash) onto the walls of the containers in the diagram below. In the second container the volume is smaller, but the number of particles is the same, so the particles collide more, because there is not much space.

Boyle's Law is used to calculate how much the pressure changes when the volume of a gas changes, provided the temperature and mass of the gas stay the same:

 

P1 × V1 = P2 × V2

 

P1 and V1 is the pressure and volume at the start, and P2 and V2 are the final pressure and volume of the gas.

Why would you hurt yourself if you pushed a pin on its pointy end?

The force would spread out.

The force would concentrate on the tip of the pointy part of the pin.

The pressure on the pointy end is smaller.

Calculate the pressure if a force of 100 N is applied on an area of 10 m2.

0.1 Pa

10 Pa

1000 Pa

What happens to water pressure as the depth of the sea increases?

increases

decreases

stays the same

Tick the correct description of liquids.

compressible

incompressible

In what kind of systems is water pressure utilised?

Choose the appropriate word to complete the sentence.

Gases are ___________.

compressible

incompressible

What is the atmospheric pressure on the surface of the Earth (at sea level)?

1000 Pa

10,000 Pa

100,000 Pa

What happens to atmospheric pressure at high altitudes?

increases

decreases

stays the same

What causes pressure in gases?

volume

temperature

collisions of particles

Use Boyle's Law to calculate the pressure inside a 200 cm3 balloon, if the initial pressure is 7 N/cm3 and you squash it to 140 cm3.

Your answer must be in N/cm3.

1540

1000

10

  • Question 1

Why would you hurt yourself if you pushed a pin on its pointy end?

CORRECT ANSWER
The force would concentrate on the tip of the pointy part of the pin.
EDDIE SAYS
The force would be concentrated on a very small area, so the pressure would be very high.
  • Question 2

Calculate the pressure if a force of 100 N is applied on an area of 10 m2.

CORRECT ANSWER
10 Pa
EDDIE SAYS
pressure = force / area = 100 N / 10 m² = 10 Pa
  • Question 3

What happens to water pressure as the depth of the sea increases?

CORRECT ANSWER
increases
EDDIE SAYS
In liquids pressure increases with depth, so in deeper water the pressure is higher.
  • Question 4

Tick the correct description of liquids.

CORRECT ANSWER
incompressible
EDDIE SAYS
Liquids cannot be squashed; they are incompressible.
  • Question 5

In what kind of systems is water pressure utilised?

CORRECT ANSWER
hydraulics
hydraulic systems
EDDIE SAYS
Hydraulic systems use pressure properties of water; for example, in car brake systems.
  • Question 6

Choose the appropriate word to complete the sentence.

Gases are ___________.

CORRECT ANSWER
compressible
EDDIE SAYS
Gases can be squashed; they are compressible.
  • Question 7

What is the atmospheric pressure on the surface of the Earth (at sea level)?

CORRECT ANSWER
100,000 Pa
EDDIE SAYS
The atmospheric pressure on the surface of the Earth is 100,000 Pa.
  • Question 8

What happens to atmospheric pressure at high altitudes?

CORRECT ANSWER
decreases
EDDIE SAYS
The number of air particles at higher altitudes decreases, so the pressure is lower.
  • Question 9

What causes pressure in gases?

CORRECT ANSWER
collisions of particles
EDDIE SAYS
Gas pressure is caused by collisions of the gas particles with the surfaces around them.
  • Question 10

Use Boyle's Law to calculate the pressure inside a 200 cm3 balloon, if the initial pressure is 7 N/cm3 and you squash it to 140 cm3.

Your answer must be in N/cm3.

CORRECT ANSWER
10
EDDIE SAYS
P1 x V1 = P2 x V2
200 x 7 = P2 x 140
P2 = 1400 / 140 = 10 N/cm³
---- OR ----

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