(c) Change of state
5.7 understand the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas
What is melting:
Changing state from solid to liquid is called melting.
What is melting point?
At a certain pressure the temperature at which a solid start melting is called melting point. The melting point of ice is 0oC.
Describe the process of melting.
When a solid is given heat, the vibration of molecules increases. The repulsion between the molecules increases. Due to greater repulsion than attraction, the molecule take greater equilibrium distance between them. If we increases temperature more, the equilibrium distance increases more. A situation comes when the molecules get separated from each other and move randomly, this state is liquid state.
What is boiling?
Changing state from liquid to gaseous state at a certain temperature is called boiling.
What is evaporation?
Changing state from liquid to gas is called evaporation.
What is boiling point?
The temperature at which a liquid start changing to gas is called boiling point.
Describe the process of boiling.
In liquid state the molecule move randomly around the vessel. If we give further heat, the speed of the molecules increases. If we continue giving heat, a speed reaches when the molecules take off from the liquid state and change into gaseous state. This is how all liquid changes into gas.
5.8 describe the arrangement and motion of particles in solids, liquids and gases
| Features | Solid | Liquid | Gas |
|---|---|---|---|
| Arrangement | Regular | Irregular | Random |
| Movement | Cannot move, vibrate only | Particles can move throughout the liquid slight past each other | Particles can move freely |
| Energy of Particles | Particles have least kinetic energy | Particles have more kinetic energy than solid | The particles have the most kinetic energy |
| Attraction between particles | Strong | Strong | Very Weak |
| Distance between particles (Density) | Tightly packed | Tend to stay close together | Far apart |
| Shape | 3D structure | Takes the shape of the container | No fixed shape |
| Compression | Cannot be compressed easily. | Cannot be compressed easily. | Can be easily compressed. |