When a solid is heated, the particles gain energy and vibrate faster until they break free from their fixed positions, having enough energy to overcome the attractions between particles. This change from solid to liquid is called melting. Each pure substance has a specific melting/boiling point, which is the temperature at which it changes state while the temperature remains constant. Boiling occurs when the most energetic particles in a liquid escape as a gas, and boiling happens throughout the entire liquid rather than just at the surface like evaporation. Sublimation is when a solid changes directly to a gas without first becoming a liquid.

1. CHANGE OF STATE

2. SOLID
ENERGY < COHESION
LIQUID
ENERGY = COHESION
GAS
ENERGY > COHESION
MELTING
BOILING
VAPORIZATION
FREEZING CONDENSATION
SUBLIMATION
DEPOSITION
REMOVING HEAT (COOLING)
ADDING HEAT

3. MELTING
When a solid is heated the particles gain energy and
vibrate faster and faster
The sructure is weakened and the particles break free
from their fixed positions (having enough energy to overcome
the atractions between particles)

4. MELTING
 Each pure substance has a specific BOILING/MELTING POINT
 (Ex: Water 100ºC, Silver 2162 ºc, Iron 1535ºC)
 Temperature remains constant during the change of state
Solid
Increasing Thermal Energy
Melting/freezing point
Liquid

5. BOILING
1. When a liquid is heated the particles move faster
2. The most energènic particles at the scape from the liquid as a vapour
3. The temperature when a solid melts is known as BOILING POINT
4. Temperature is constant while the boiling is taking place.
5. It happens in all the liquid, not just in the surface

6. Some boiling amb melting examples….
Substance
Melting Point
(ºC)
Boiling Point
(ºC)
Water 0 100
Alcohol - 114 78,5
Oxigen - 218 - 183
Iron 1538 2861
Mercury - 39 357

7. It takes place only on the surface of the liquid
Some particles in liquids have more energy than others
The more energetic particles take energy from the liquid to become a gas.
And the liquid cool down
 Evaporation is produced at room temperature (at any temperature)
Examples: puddles (when they get dry), when we get cold after sweeting…
EVAPORATION
canvis d’estat
estats de la matèria

8. BOILING
EVAPORATION

9. SUBLIMATION
Matter changes straight from a solid to a gas!
Molecules speed up and spread out rapidly
Examples: Naftalina, dry ice, deodorant

10. SUBLIMATION
Matter changes straight from a solid to a gas!
Molecules speed up and spread out rapidly
Examples: Naftalina, dry ice, deodorant