1. Heating Solids, Liquids & Gases
To understand what happens to solids, liquids and gases when they are heated

2. Particle Model
What is the particle model, and what are the key characteristics of a solid, liquid and gas?
The particle theory states that all things are made of tiny pieces, called particles
Solids, liquids and gasses all have different arrangements of these particles, giving them their special properties…
Solids
Liquids
Gases

3. Particle Model Solids Liquids Gases State Solid Liquid Gas
Arrangement of particles
Movement of particles
Close together
Regular pattern
Close together
Random
Far apart
Random
Vibrate on the spot
Move around each other
Move quickly in all directions

4. Heat
What happens to these particles when they are heated (given thermal energy)?
What happens to these particles when they are cooled?
When particles are given more thermal energy (heat) they take up more room and expand, and when this is taken away they take up less room and contract
How could you prove this?

5. Heating
Look at the ball and ring - the ball can pass through the ring easily
But… when the ball is heated (given thermal energy) it cannot pass through the ring!
However, if we heat them both, the ball passes through the ring
This shows that as an object is given more thermal energy its particles take up more room

6. Cooling
When the ball is allowed to cool, it suddenly passes through the hoop again
Also, a heated glass rod will shatter if placed into iced water
This is because the glass rod is cooled so quickly parts of it contract at such a rate that stresses cause it to shatter

7. Expansion & Contraction
What happened when we heated the ball?
Substances expand (get bigger) when they are heated up
What happened when we rapidly cooled the glass?
Substances contract (get smaller) when they are cooled

8. Expansion & Contraction
Substances expand (get bigger) when they are heated up
The particles stay the same (the number of particles + their size is the same)
But they take up more room!
When heated: -
Solids - particles vibrate more and take up more room
Liquids - move around each other more quickly and take up more room
Gases - move more quickly in all directions, and take up more room
Substances contract (get smaller) when they are cooled down
When we cool objects, the number of particles and their size remains the same, they just take up less room!

9. Expansion & Contraction
Look at the example of the cylinder and the hole
Substances expand when they are heated
Substances contract when they are cooled
Role play expansion & contraction…

10. Problems & Uses
Expansion joint in a bridge
Expansion of substances can be both useful, and cause problems for designers and engineers - can you think of any?
Problem - bridges expand in the summer, and need special joints to stop them bending out of shape
Concorde (the supersonic plane) expanded when it was going at very high speed by ~30cm!
Thermometers use liquids which expand when they get hotter, and contract when the get colder - very useful for us to measure heat!
At very high speed friction causes a great deal of heat - this expands the plane in a variety of areas

11. Temperature & Thermal Energy
How can we model the difference between high temperature, and high thermal energy?
Thermal energy (heat) is the energy that a substance possesses due to the kinetic energy of its particles
Temperature is a measure of the average kinetic energy of the molecules of a substance
A few gas particles – this can be a high temperature (average kinetic energy) but the thermal energy (heat) it has is small as there are not that many particles
Many gas particles – this can be a high temperature (average kinetic energy) but the thermal energy (heat) it has is much larger as there are many more particles

12. Accident
Imagine a spoonful of 100oC water and a tank filled with water, also at 100oC
Which would you rather have spilled on you?
The water in the tank can transfer much more heat, despite the fact that its temperature is no higher that the water in the spoon