2. Chapter Ten: Matter and Temperature
10.3 The Phases of Matter

3. 10.2 Temperature There are two common temperature scales.
On the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees.
The Celsius scale divides the interval between the freezing and boiling points of water into 100 degrees.

6. Solving Problems
A friend in Paris sends you a recipe for a cake. The French recipe says to bake the cake at a temperature of 200 °C for 45 minutes.
At what temperature should you set your oven, which uses the Fahrenheit scale?

7. Looking for: Given: Relationships: Solution Solving Problems
…temperature in degrees Fahrenheit
Given:
…temperature 200 C
Relationships:
TF = 9/5 TC + 32
Solution
TF = (9/5)(200 °C) + 32 = 392 °F

8. 10.2 What temperature really is
Atoms are in constant motion, even in a solid object.
The back-and-forth jiggling of atoms is caused by thermal energy, which is a kind of kinetic energy.

9. 10.2 What temperature really is
Temperature measures the kinetic energy per molecule due to random motion.

10. 10.2 Thermometers
A thermometer is an instrument that measures the exact temperature.
Most thermometers contain either a silvery fluid (mercury) or a red fluid, which is alcohol containing a small amount of red dye.

11. 10.2 How a thermometer works
The volume of alcohol in a thermometer contains huge numbers of alcohol molecules.
As temperature increases, the alcohol molecules move faster and bounce off each other.
The liquid alcohol expands and takes up more space in the thermometer.

12. 10.2 Measuring temperature
A thermistor is a device that changes its electrical resistance as the temperature changes.
Some digital thermometers sense temperature by measuring the resistance of electrons passing through wire.

13. 10.2 Liquid-crystal thermometers
Some thermometers contain liquid crystals that change color based on temperature.
As temperature increases, the molecules of the liquid crystal bump into each other more and more.
This causes a change in the structure of the crystals, which in turn affects their color.

14. 10.2 Absolute zero Absolute zero is -273°C.
You cannot have a temperature lower than absolute zero.
Think of absolute zero as the temperature at which atoms are “frozen.”

15. 10.2 Converting to Kelvin
The Kelvin temperature scale is useful in science because it starts at absolute zero.
To convert from Celsius to Kelvin, you add 273 to the temperature in Celsius.

16. 10.3 Phases of Matter
On Earth, pure substances are usually found as solids, liquids, or gases.
These are called phases of matter.

17. 10.3 The phases of matter A solid holds its shape and does not flow.
The molecules in a solid vibrate in place, but on average, don’t move far from their places.

18. 10.3 The phases of matter
A liquid holds its volume, but does not hold its shape—it flows.
Liquids flow because the molecules can move around.

19. 10.3 The phases of matter
A gas flows like a liquid, but can also expand or contract to fill a container.
A gas does not hold its volume.
The molecules in a gas have enough energy to completely break away from each other.

20. 10.3 The phases of matter
When they are close together, molecules are attracted through intermolecular forces.

21. 10.3 The phases of matter
The forces in chemical bonds are stronger than intermolecular forces.

22. 10.3 Intermolecular forces
Within all matter, there is a constant competition between temperature and intermolecular forces.
When temperature wins the competition, molecules fly apart and you have a gas.
When intermolecular forces win the competition, molecules clump tightly together and you have a solid.

23. 10.3 Melting and boiling
The melting point is the temperature at which a substance changes from a solid to a liquid.

24. 10.3 Melting and boiling
The temperature at which a liquid becomes a gas is called the boiling point.

25. Notice temperature is constant while ice melts!
As heat energy is added to ice, the temperature increases until it reaches 0°C.
Then the temperature stops increasing.
As you add more heat, more ice becomes liquid water but the temperature stays the same.
This is because the added energy is being used to break the intermolecular forces and change solid into liquid.
Once all the ice has become liquid, the temperature starts to rise again if more energy is added.

26. 10.3 Melting and boiling points of common substances
Materials have a wide range of melting and boiling points.

27. 10.3 Sublimation
Sometimes a solid can change directly to a gas when heat energy is added.
This process is called sublimation.

28. Chapter Eleven: Heat
11.1 Heat
11.2 Heat Transfer

29. 11.1 What is heat? Heat is thermal energy that is moving.
Heat flows any time there is a difference in temperature.
Because your hand has more thermal energy than chocolate, thermal energy flows from your hand to the chocolate and the chocolate begins to melt.

30. 11.1 What is heat?
Heat and temperature are related, but are not the same thing.
The amount of thermal energy depends on the temperature but it also depends on the amount of matter you have.

31. 11.1 Units of heat and thermal energy
The metric unit for measuring heat is the joule.
This is the same joule used to measure all forms of energy, not just heat.

32. 11.1 Heat and thermal energy
Thermal energy is often measured in calories.
One calorie is the amount of energy it takes to raise the temperature of one milliliter of water by one degree Celsius.

33. 11.1 Specific heat
The specific heat is a property of a substance that tells us how much heat is needed to raise the temperature of one kilogram of a material by one degree Celsius.
Knowing the specific heat of a material tells you how quickly the temperature will change as it gains or loses energy.

34. 11.1 Why is specific heat different for different materials?
Temperature measures the average kinetic energy per particle.
Energy that is divided between fewer particles means more energy per particle, and therefore more temperature change.
In general, materials made up of heavy atoms or molecules have low specific heat compared with materials made up of lighter ones.

36. 11.1 The heat equation

37. Solving Problems
How much heat is needed to raise the temperature of a 250-liter hot tub from 20°C to 40°C?

38. Solving Problems Looking for: Given: Relationships: Solution:
…amount of heat in joules
Given:
V = 250 L, 1 L of water = 1 kg
Temp changes from 20°C to 40°C
Table specific heat water = 4, 184 J/kg°C
Relationships:
E = mCp(T2 – T1)
Solution:
E = (250L × 1kg/L) × 4,184 J/kg°C (40°C - 20°C) = 20,920,000 J
Sig. fig./Sci. not. 20,920,000 J = 2.1 x 107 J

39. 11.2 Heat transfer
Heat conduction is the transfer of heat by the direct contact of particles of matter.
Conduction occurs between two materials at different temperatures when they are touching each other.
Where is the heat energy conducted to and from in this system?

40. 11.2 Heat transfer
Thermal equilibrium occurs when two bodies have the same temperature.
No heat flows in thermal equilibrium because the temperature is the same in the two materials.

41. 11.2 Thermal conductors and insulators
Materials that conduct heat easily are called thermal conductors and those that conduct heat poorly are called thermal insulators.
Is a down coat a conductor or an insulator?

43. 11.2 Convection
Convection is the transfer of heat through the motion of matter such as air and water.
The hot water at the bottom of the pot rises to the top and replaces the cold water.

44. 11.2 Convection
Convection is mainly what distributes heat throughout a room.

45. 11.2 Thermal radiation
Heat from the Sun is transferred to Earth by thermal radiation.
All the energy the Earth receives from the Sun comes from thermal radiation.
The higher the temperature of an object, the more thermal radiation it emits.

46. 11.2 Thermal radiation Thermal radiation is also absorbed by objects.
The amount of thermal radiation absorbed depends on the surface of a material.
Dark surfaces absorb most of the thermal radiation they receive.
Silver or mirrored surfaces reflect thermal radiation.

47. 11.2 Heat transfer, winds, and currents
A thermal is a convection current in the atmosphere.
When a surface, like a road absorbs solar radiation, it emits energy as heat.
The warmed air molecules gain kinetic energy and rise.
Colder air is forced aside and sinks.

48. 11.2 Thermal radiation
There are giant convection currents in Earth’s atmosphere.
The global wind patterns and Earth’s rotation also cause surface ocean currents to move in large circular patterns.