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What is temperature?
The measure of the average kinetic energy of the particles in an object Thermal Energy and temperature Video
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If 2 substances have the same temperature then they have the same __________________________. How do we know?
Well, temperature is the measure of the amount of kinetic energy of the molecules in an object. So, if 2 substances have the same temperature then they have the same average kinetic energy. 3
What determines the temperature of a substance?
Temperature is determined by how fast the atoms or molecules of a substance are moving.
There are several ways to measure the temperature. These are called temperature scales. Name 1: 4
Fahrenheit­­based on the freezing and boiling points of water
32 F= freezing point of water
212 F= boiling point of water
Celsius­­based on the freezing and boiling points of water
0 C= freezing point of water
100 C=boiling point of water
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Kelvin is the SI scale for temperature
What is the lowest possible temperature?
0 K
Kelvin­­based on absolute Zero
0 K­­ absolute zero (no Kinetic Energy)
273 K­­feezing point of water
373 K­­boiling point of water
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Thermometers­­a device that measures changes in average kinetic energy How do thermometers work?
Due to thermal expansion­­the increase in volume of a substance due to an increase in temperature
Alcohol in a thermometer rises as a result of this. Most bridges and side walks are constructed with gaps called expansion joints so that there is room for the materials to expand when the temperature increases. 8
How does thermal energy differ from temperature?
Thermal energy is the total amount of kinetic energy of the particles in a substance while temperature measures the average kinetic energy of the particles in the substance.
Temperature, unlike thermal energy, does not depend on the mass. 9
Which has more thermal energy?
Hill
Mountain
both at 20 C
The mountain has more mass therefore it has much more thermal energy
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Which has more thermal energy?
Hot chocolate?
The Atlantic Ocean?
The Atlantic Ocean because it has a much larger mass
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Activity 1: Moving Molecules in a Solid
Moving Molecules in a Solid
Complete Activity Worksheet During Ring and Metal Ball Demo
Activity 2: The Ups and Downs of Thermometers Heating and Cooling a Thermometer
Materials: thermometer
magnifying glass
cold water
hot water
Follow instructions on activity sheet "The Ups and downs of thermometers" 12
Heat Transfer
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Heat transfer Activity
• You will be divided into groups.
• Each group will be assigned a type of heat transfer.
• You and your group will define the type of heat transfer, describe an example, and draw a picture.
• You will present what you discussed to the class 14
The 3 types of heat transfer: 1. Radiation­­The transfer of energy through __________ or _________ as electromagnetic waves
• Warmth from a campfire
• greenhouse trap radiant energy
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2. Conduction­­ the transfer of thermal energy from one object to another through direct contact. Examples: the handle of a metal spoon warms up when it is placed in a hot bowl of soup because of conduction
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Conductors are materials that easily transfer thermal energy. Some good conductors are metal and glass. Some bad conductors water, plastic, rubber, wood, etc.
If a substance is a bad conductor it is an insulator. An insulator is a material that resists the transfer of thermal energy.
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3. Convection­­the transfer of thermal energy by the movement of a liquid or a gas
In a warm­air heating system, warm air is circulated through the rooms by convection currents. This is also what causes pots of water to boil or how convection ovens works (most ovens).
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The transfer of energy between objects that are at different temperatures.
Are heat, thermal energy, and temperature the same thing?
In groups, create a table comparing and contrasting the three 20
Heat
Thermal Energy
Temperature
Similarities
• Deals with KE
• Deals with KE
• Deals with KE
Differences
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Heat and thermal energy are not the same thing. Heat is the transfer of thermal energy. Objects contain thermal energy but they DO NOT contain Heat. Think of heat as a verb (action word)!
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What's the matter with Heat?
Let's review particle theory
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Solids­­­ the particles do not have enough kinetic energy to overcome the attraction between them. They move the slowest and vibrate in place.
Liquids­­­ the particles have enough kinetic energy to overcome some of the attraction between them and slide past each other.
Gas­­­ the particles have enough kinetic energy to overcome nearly all of the attraction between them and move independently of each other
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Matter can change from state to state with the addition of thermal energy. A change of state is when matter changes from one physical form to another. It DOES NOT change the identity of the substance. Water is still water whether it is a solid, a liquid, or a gas. 25
Physical and Chemical Changes What type of change is a change of state?
It's a physical change! The identity of the matter is the same!
So a physical change is a change that affects one or more physical properties of the substance. Physical changes DO NOT affect the type of substance it is.
Ex: melting, freezing, boiling, vaporizing
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During a chemical change, one or more substances combine to form one or more new substances. Clues: burning, change odor, bubbling, change in color. 27
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Important to Remember:
While changing states the temperature does not change. The heat changes the arrangement of the particles
Where on the phase change diagram is a change of state?
According to the chart, at what temperature does the water change from water to steam?
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Applications of Heat
Heat engines­­machines that use heat to do work. These are engines in cars, trains, steam boats, planes, etc. Fuel is burned and the expanding gases are used to do work
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Heat Pump­­­ Moves heat from an area of low temperature and pushes it to an area of high temperature. It takes mechanical work
These are air conditioners, refrigerators, and heat pumps that warm our houses. 31
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