1. The Particle Model and Changes of State
Unit 3 - Topic 5

2. Representing the 3 States of Matter
Divide the class into three (3) groups.
Group 1 – Arrange yourselves to demonstrate the arrangement and movement of particles in a solid.
Group 2 – Arrange yourselves to demonstrate the arrangement and movement of particles in a liquid.
Group 3 – Arrange yourselves to demonstrate the arrangement and movement of particles in a gas.

3. The 3 States of Water What are the three states of water?
How does water move from one state to another?
What do you think happens to the particles as water moves from one state to another?

4. States & Particle Model - Review
Solids
Liquids
Gases
Size & Shape
Keep their shape
Take the shape of the container
No definite shape
Compressibility (volume)
Can’t be compressed (fixed volume)
Almost incompressible (fixed volume)
Can be compressed (volume changes)

5. Add thermal energy… Substances expand by different amounts
their temperatures rise differently
change state

6. Add thermal energy… Substances expand by different amounts
concrete vs. steel vs. glass (see page. 211)

7. Add thermal energy… Substances’ temperatures rise differently
Given the same heat…
Sand warms and cools quickly
Water warms and cools slowly
Due to (pg. 218):
Heat capacity
Specific heat capacity

8. Add thermal energy… Substances change state:
Melting (fusion) solid  liquid
freezing (solidification) liquid  solid
evaporation: liquid  gas
condensation: gas  liquid
sublimation: gas  solid
sublimation: solid  gas

9. Changes of State

10. Temperature During Change of State
Temperature constant = avg. speed of particles constant
Speed of particles changes = temperature changes
Arrangement of the particles changes
Particles become less organized as their energy increases (just like students!)
Particles become more organized as their energy drops

11. Check your notes!
Solid
Gas

12. Pure Substances Can exist in all 3 states of matter Examples
water, hydrogen, gold
Non – examples
paints, plastics
not able to melt and then return
to a solid or gas form

13. Most substances not easy to study
Hydrogen (H2)
a gas, even at coldest winter temperatures
to make liquid H2, cool H2 gas to -235oC
to make solid H2, extreme cold temperatures and high pressures required

14. Melting and Boiling Points
Vital pieces of information – and not only for scientists Why?
Solid  Liquid
Liquid  Gas
Substance
Melting Point (oC)
Boiling Point (oC)
Oxygen
-218
-183
Mercury
-39
357
Water
100
Table salt
801
1413
Silver
962
2162
Gold
1064
2856
Iron
1535
2861

15. When a Liquid Evaporates
In a liquid, particles move at many different speeds
At the surface of a liquid, some of the faster moving particles are able to escape into the air
Slower moving particles stay in the liquid state

16. When a Liquid Evaporates
Slower motion = lower average energy = lower temperature
As the higher energy particles leave the surface, the remaining liquid is cooler than the original liquid, which helps cool lower particles
This phenomenon is called EVAPORATIVE COOLING

17. To summarize… Specific Heat Capacity vs. Heat Capacity
Adding thermal energy to substances
6 changes of state
Temperature constant during change of state
Arrangement of particles changes during change of state
Evaporative cooling