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

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

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

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?

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

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

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

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!

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…

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

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

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