1. Heat and States of Matter
Chapter 9

2. Temperature and Thermal Energy
Section 1

3. Kinetic Theory of matter
All around you objects are warming and cooling
What causes the temperature of an object to change?
Temperature is related to the motion of the particles of matter than make up an object
The Kinetic theory of matter describes the motion of the particles
Matter is made up of atoms, molecules, or ions that are constantly in random motion
Particles in motion will have kinetic energy
When particles collide they will transfer kinetic energy from one particle to another

4. Temperature Temperature Temperature scales
Measure of the average kinetic energy of its particles
AS average kinetic energy increases, temperature increases
Temperature scales
Kelvin (K) SI unit
Celsius (oC)
Fahrenheit (oF)

5. Temperature conversions
Celsius to Kelvin
K = oC + 273
Celsius to Fahrenheit
oC = (5/9)(oF – 32)
Fahrenheit to Celsius
oF = (9/5) oC + 32

6. Let’s Practice
What is -40 o F in degrees Celsius?

7. Here’s another one…
What is the temperature of 22 oC in degrees Fahrenheit?

8. One more…
What is 25 oC in Kelvin?

9. Thermal Energy
Not only are particles in matter constantly in motion, they are attracted to one another
AS the particles move further apart, they gain potential energy
The sum of all the kinetic and potential energy of all the particles of an object is the thermal energy

10. Heat
Heat
Thermal energy that flows from something at a higher temperature to something at a lower temperature
Form of energy
Measured in Joules
Always flows from warmer materials to cooler materials

11. Specific Heat
SPECIFIC HEAT OF SOME COMMON MATERIALS
Different objects will change temperature faster than others
As a substances is heated, temperature changes depends on:
The amount of thermal energy added
Nature of the substance
Specific heat is the amount of thermal energy required to raise the temperature of 1 kg of some material by 1 oC
Measured in J/(kg oC)
Substance
Specific Heat J/(kg oC)
Water
4,194
Ice
2,110
Asphalt
920
Glass
800
Iron
450

12. Changes in Thermal energy
Changes in thermal energy are calculated using the following equation:
Q = m x ΔT x C
Q = Change in thermal energy (j)
M = Mass (kg)
ΔT = change in temperature (final temp – initial temp)
C = specific heat of the substance

13. Let’s Try it…
The air in a living room has a mass of 72 kg an. d a specific heat of 1,010 J/(kgoC). What is the change in thermal energy of the air when it warms from 20oC to 25oC?

14. Measuring specific Heat
A Calorimeter is used to measure specific heat
IN a Calorimeter, a heated sample transfers thermal energy to a known mass of water.
The energy absorbed by the water is calculated
Energy absorbed = energy released by the sample

15. States of Matter
Section 2

16. Four states of Matter Solid Liquid Gas Plasma
Tightly packed particles vibrating in space
Fixed Shape and volume
Liquid
Attractive forces are weaker than in solid
Particles slide past one another allowing flow
Definite volume not specific shape
Gas
Particles are further apart
Attractive forces are very weak
NO definite volume or shape
Plasma
Most common
Consists of positive and negative charged particles with no definite shape or volume
Results from collisions between molecules moving at high speeds

17. States of Matter

18. Changing states
Changes in thermal energy cause substances to change from one state to another
Melting
Energy must be added until particles move out of their ordered arrangement
Energy required to change 1 kg of a substance from a solid to a liquid is the heat of fusion
Melting point is the temperature where as solid starts to melt

19. Changing states Freezing Energy is released
Particles move slower and the attraction between particles increase so that they form an ordered arrangement
The amount of energy released is also the heat of fusion
Freezingheat released (negative value)
MeltingHeat absorbed (positive value)

20. Changing state Vaporization Particles move faster
Attractive forces weaken
Particles not longer cling to each other
Evaporation occurs at the surface of the liquid
Evaporation causes the surface of the liquid to decrease
Heat of vaporization is the amount of energy required for 1 kg of the liquid to become a gas at boiling point

21. Changing state Condensation Gas particles slow down
Attractive forces increase
Return to liquid state
The amount of energy released is also the heat of vaporization
Vaporizationenergy absorbed (positive value)
CondensationEnergy released (negative value)

22. Heating Curve of a substance
HEATING CURVE OF WATER
When the system is heated, energy is transferred into it.
In response to the energy it receives, the system changes, for example by increasing its temperature.
A plot of the temperature versus time is called the heating curve.

23. Thermal Expansion
Solids, liquids, and gases will expand and contract with fluctuations in temperature
Slower moving particles will be closer together smaller volume
Faster moving particles will be further apartlarger volume

24. Transferring thermal energy
Section 3

25. Ways to transfer thermal energy
Conduction
Convection
Radiation

26. Conduction Thermal energy can be transferred when particles collide
This type of energy transfer is know as conduction
Particles closest to the heat source speed up, collide with nearby slow moving particles, and ultimately passing energy throughout the sample
Required contact

27. convection
Convection is the transfer of thermal energy by movement of a fluid or gas
Particles gain energy from heat source.
Warm air is less dense and will rise.
As warm air is rising, cool air from the side replaces heated air causing a circular convection current.

28. Radiation Radiation is the transfer of energy by electromagnetic waves
Energy transferred by radiation is called radiant energy
Radiation can pass through solids, liquids, and gases

29. Thermal Insulators
Thermal insulators are materials in which thermal energy moves slowly
Examples of thermal insulators
Some plastics
Wood
Fiberglass
Air