Changing States of Matter

1.2 understand how the interconversions of solids, liquids and gases are achieved
and recall the names used for these interconversions.

                      

1.3 explain the changes in arrangement, movement and energy of particles
during these interconversions

Solid > Liquid
This is achieved through a process called melting. The solid is heated, causing it's particles to gain more energy and vibrate. This weakens the forces that hold the solid together, making the solid expand. At a certain temperature (it's melting point), the particles will have enough energy to break free from their positions and thus the solid turns into a liquid. 

Liquid > Solid
This is achieved through a process called freezing, or solidifying. In this process, heat is removed. When a liquid is cooled, the particles lose energy and slow down. They eventually stop moving, apart from vibrating in their fixed position. A solid has now been formed. 

Liquid > Gas
A liquid becomes a gas through a process known as evaporating. In this process, heat is supplied. When a liquid is heated, the particles gain more energy and this causes the particles to vibrate/move faster. This weakens and breaks the bond holding the liquid together, as the particles break away from eachother and expand (this will happen at a certain temperature). The liquid has now become a gas. 

Gas > Liquid 
The process of turning a gas into a liquid is known as condensing. Like freezing, within this process heat is removed. When you cool a gas, the particles will lose energy. This loss in energy causes the particles to move at a much slower pace as they move closer together. Eventually, the particles will no longer have sufficient energy to move away as they bump into one another, and when this happens, the gas has become a liquid.

Solid > Gas 
A solid becomes a gas through a process known as sublimation (subliming). Sublimation refers to a solid becoming a gas , without becoming a liquid during this process. These reactions occur at temperatures and pressures below the triple point, ("the particular temperature and pressure at which the solid, liquid, and gaseous phases of a given substance are all at equilibrium with one another.") This means that the particles will have too much energy to remain in a liquid state and will instead become a gas. 

Gas > Solid 
A gas becomes a solid in a process known as deposition. This process refers to a gas becoming a solid, and like sublimation, not going through a liquid phase in the process. This occurs when the temperature or pressure is below the triple point, and therefore the particles will have too little energy to move around and remain in liquid form, so they form a solid.