Chapter 11
Temperature, Heat, & Phases of Matter
Name ______________________________
7th grade Science
Period ______
1. Fahrenheit – A temperature scale that has water freezing at 32 degrees, and boiling at 212
degrees, is the Fahrenheit scale. There are 180 Fahrenheit degrees between the freezing point
and boiling point of water. The U. S. uses this scale. (pg. 276)
2. Celsius – The Celsius temperature scale has water freezing at zero and boiling at 100 degrees.
Most scientists use this scale. To convert Fahrenheit into Celsius and back again use the
following formulas: Tfahrenheit = 9/5 Tcelsius + 32 Tcelsius = 5/9 (Tfahrenheit - 32) (pg. 276)
3. Thermometer– An instrument that measures temperature is called a thermometer. (pg. 276)
4. Kinetic Energy – The kinetic theory tells us that tiny particles of matter (atoms and
molecules) never stop moving. This energy of movement is called kinetic energy.
5. Thermal Energy – Thermal energy is the energy in an object created by temperature (heat).
Adding heat increases the energy of molecules and they move faster, with more motion, and
get farther apart (kinetic energy). Cooling takes thermal energy (heat) away and molecules
move slower, with less kinetic energy, and get closer together. (pg. 278)
6. Thermal Expansion/Contraction – Matter expands when you add thermal energy (heat)
because the molecules get farther apart. This is called thermal expansion. Matter contracts
when it is cooled because the molecules get closer together. This is called thermal contraction.
7. Random Motion & Temperature – When kinetic energy (motion) scatters equally in all
directions this is called random energy. The random energy of each atom in a substance is
called random motion. Temperature is a measurement of the kinetic energy in each atom due
to this random motion. Remember that it is the amount of heat that effects the movement of
the atoms. (278)
8. Average Motion - Kinetic energy can also be a measurement of the average motion of all the
atoms in a substance together. This is not a temperature measurement. It is a speed
measurement. Example: When you throw a rock it has velocity (kinetic energy). All of
the atoms in the rock are moving together in a certain direction at a certain speed. (pg. 278)
9. Absolute Zero – When molecules have the lowest energy they can have, and the temperature
cannot get any lower, this is called absolute zero. Thermal energy (heat) is at its lowest
possible levels and is as close to zero as it can be (about -273 degrees Celsius).
Note: There is no highest possible temperature. Temperature can go up indefinitely. (pg. 279)
10. Kelvin Scale – The temperature scale that starts at absolute zero is called the Kelvin scale.
The Kelvin scale goes up in units identical to the Celsius scale. Water freezes at 273
degrees K, and boils at 373 degrees K. To convert to Kelvin you add 273.16 to the Celsius
temperature (21 degrees C + 273.16 = 294.16 degrees K). (pg. 279)
11. Solid – A state of matter that holds its shape and does not flow is called a solid. Solids also
hold their volume. Molecules in a solid vibrate in place but do not move far from their
positions. Most solids are locked closely together in crystals (a regular, orderly arrangement
of atoms). Solids are the most dense forms of matter.
Note: Some solids such as glass, many plastics, rubber, and wax appear to be solids but they
have no crystals. The atoms have a random and jumbled arrangement. These solids are called
amorphous solids. (pg. 280, 314)
12. Liquid – A liquid is a state of matter that holds its volume but will not hold its shape. A
liquid flows and easily changes shape. Liquids are about as close together as solids but they
have enough energy to move around freely and change positions. They have broken their
crystals. (pg. 280)
13. Gas – A gas flows like a liquid but can also expand or contract to fill a container. A gas does
not hold its volume. Gas molecules have enough energy to completely spread away from
each other and are much farther apart than solid or liquid molecules. (pg. 280)
14. Plasma – At temperatures greater than 10,000 degrees Celsius the atoms of gases begin to
come apart forming positive and negative ions. This phase of matter is called plasma.
Plasma is formed in lightning and inside stars. (pg. 279)
15. Intermolecular Forces – Forces between molecules that determine which phase of
matter they will be are called intermolecular forces. These are weaker forces than the
chemical bonds that hold atoms together forming compounds. (pg. 280)
16. Melting Point/Freezing Point – The point at which a solid gains enough heat to melt into
a liquid, or a liquid loses enough heat to freeze into a solid. Different substances have
different melting and freezing points. When something melts the atoms vibrate more
vigorously, break their crystals, and begin to move freely. When something freezes the atoms
slow down and lock back into crystals, losing the ability to move freely. They simply vibrate
in place. (pg. 281)
17. Boiling Point/Condensation Point – The point at which a liquid gains enough heat energy
to boil into a gas, or a gas loses enough heat to condense into a liquid. Different substances
have different boiling and condensation points. (pg. 281)
18. Evaporation - When a liquid changes to a gas gradually, at temperatures below the boiling
point, this is called evaporation. Evaporation is usually caused from radiation from the sun.
19. Phase Change – As the temperature of solid gains heat energy it reaches melting point and
begins to change phase to a liquid. During the phase change temperature stays constant
because all of the heat energy is being used to break the solid into a liquid. As the
temperature of a liquid rises it will reach boiling point and the liquid will change phase to a
gas. Again during the phase change temperature remains constant. (pg. 281)
20. Pressure – Pressure can be used to cause phase changes in gases. Pressure forces molecules
closer together. Lack of pressure allows molecules to spread apart. Applying enough pressure
to a gas, and cooling it at the same time, can turn it into a liquid, or even a solid.
21. Sublimation - When a solid gains enough thermal energy to change phase directly to a gas,
skipping the liquid stage, this is called sublimation.
22. Heat – Thermal energy that is moving or capable of moving is called heat. It takes twice as
much energy to heat 2000 grams of water as it does to heat 1000 grams of water. (pg. 283)
23. Joule – The metric unit used to measure heat is called the Joule. (pg. 284)
24. Calorie – One calorie is the amount of heat energy needed to raise the temperature of 1 gram
of water 1 degree Celsius. One calorie is equal to 4.186 joules. The unit used to measure the
energy of the food we eat is the kilocalorie. A kilocalorie in food equals 1000 calories.
Example: a cookie containing 210 food calories contains 210,000 units of heat
calories. (pg. 284)
25. British Thermal Unit (Btu) – An amount of energy needed to raise 1 pound of water 1
degree Fahrenheit is called a British thermal unit. One Btu is equal to 1055 joules. (pg. 284)
26. Specific Heat – The amount of heat needed to raise the temperature of 1 kilogram of a
material by 1 degree Celsius is called specific heat. The specific heat of water is 4184J/Kg C.
The heavier an object is the lower its specific heat. (pg. 286)
27. Heat Transfer – The flow of heat from higher temperature to lower temperature is called
heat transfer. (pg. 287)
28. Conduction – The transfer of heat from particle to particle by direct contact is called conduction.
29. Thermal Equilibrium – When things are at the same temperature and no heat flows back
and forth between them this is called thermal equilibrium. (pg. 287)
30. Thermal Conductors & Thermal Insulators – Materials that easily conduct heat are called
thermal conductors. Materials that conduct heat poorly are called thermal insulators. (pg. 288)
31. Convection – The transfer of heat by the flow (movement) of heated matter is called convection.
Hot air rises and cold air sinks causing convection currents. Liquids also act in the same
manner. (pg. 289)
32. Thermal Radiation – The transfer of heat by electromagnetic waves (including light) is called
thermal radiation. Heat from the sun gets to us by thermal radiation. Unlike conduction and
convection thermal radiation can travel through the vacuum of space. It does not need any medium
to move through. (pg. 290)