1. Temperature, Thermal Energy, and Heat (Section 5.1)
5(A) recognize and demonstrate that objects and substances in motion have kinetic energy such as vibration of atoms, water flowing down a stream moving pebbles, and bowling balls knocking down pins.
4(A) Describe and calculate an object’s motion in terms of position, displacement, speed, and acceleration.
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Temperature, Thermal Energy, and Heat

2. Essential Questions What is temperature?
How are thermal energy and temperature related?
What is the difference between thermal energy and heat?
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Temperature, Thermal Energy, and Heat

3. Vocabulary Review New energy temperature thermal energy heat
specific heat
Temperature, Thermal Energy, and Heat
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4. Matter is made of atoms and molecules
Matter in Motion
Matter is made of atoms and molecules
Particles are in constant, random motion
Faster they move, the more kinetic energy they have
Particles in hot objects move faster than in slow objects
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Temperature, Thermal Energy, and Heat

5. Temperature
measure of the average kinetic energy of the particles that make up that object.
Temperature increase = increase in average speed of particles
measured in kelvins (K).
A more commonly used temperature scale is the Celsius scale.
One kelvin is the same as one degree Celsius.
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Temperature, Thermal Energy, and Heat

6. Thermal Energy Introduction
If you let cold butter sit at room temperature for a while, it warms and becomes softer.
Because the air in the room is at a higher temperature than the butter, particles that compose air have more kinetic energy than the particles that compose butter.
Collisions between the particles that compose butter and the particles that compose air transfer energy from the faster-moving air particles to the slower- moving butter particles.
The particles that compose butter then move faster and the temperature of the butter increases.
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Temperature, Thermal Energy, and Heat

7. Thermal Energy
sum of the kinetic energy and potential energy of all the particles that compose an object
Because the kinetic energy of the butter particles increased as the butter warmed, the thermal energy of the butter increased.
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Temperature, Thermal Energy, and Heat

8. Thermal Energy and Temperature
When the temperature of an object increases, the average kinetic energy of the particles that compose the object increases.
Because thermal energy is the total kinetic and potential energy of all the particles that compose an object, the thermal energy of the object increases when the average kinetic energy of its particles increases.
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Temperature, Thermal Energy, and Heat

9. Heat
thermal energy that is transferred from something at a higher temperature to something at a lower temperature.
measured in joules
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Temperature, Thermal Energy, and Heat

10. Specific Heat
The amount of heat that is needed to raise the temperature of 1 kg of a substance by 1°C
As a substance absorbs thermal energy, its temperature change depends on the nature of the substance, as well as the amount of thermal energy that is added.
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Temperature, Thermal Energy, and Heat

11. Specific Heat
Because water can absorb thermal energy without a large change in temperature, it is useful as a coolant.
A coolant is a substance that is used to absorb thermal energy.
Compared with the other common materials in the table, water has the highest specific heat.
The specific heat of water is high because water molecules are strongly attracted to each other.
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Temperature, Thermal Energy, and Heat

12. Water Has High Specific Heat
When thermal energy is added, some of the added thermal energy has to break some of the attractions between the water molecules before they can move faster.
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Temperature, Thermal Energy, and Heat

13. Metals Have Low Specific Heat
In metals, electrons can move freely. When thermal energy is added, no strong attractions have to be broken before the electrons can start moving faster.
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Temperature, Thermal Energy, and Heat

14. Changes in Thermal Energy
The thermal energy of an object changes when thermal energy is transferred into or out of the object.
If Q is the change in thermal energy and C is specific heat, the change in thermal energy can be calculated from the following equation:
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Temperature, Thermal Energy, and Heat

15. SOLVE FOR THERMAL ENERGY
Use with Example Problem 1.
Problem
A wooden block has a mass of 20.0 kg and a specific heat of 1,700 J/(kg · °C). Find the change in thermal energy of the block as it warms from 15.0°C to 25.0°C.
SOLVE FOR THE UNKNOWN
Set Up the Problem
Q = m(Tf – Ti)C
Solve the Problem
Q = (20.0 kg)(25.0°C – 15.0°C)(1,700 J/(kg ·°C))
= (20.0 kg)(10.0°C)(1,700 J/(kg ·°C))
= 340,000 J
Response
ANALYZE THE PROBLEM
KNOWN
mass: m = 20.0 kg
final temperature: Tf = 25.0°C
initial temperature: Ti = 15.0°C
specific heat: C = 1,700 J/(kg · °C)
UNKNOWN
change in thermal energy: Q
EVALUATE THE ANSWER
Do the units match on both sides of the equation? Changes in thermal energy (Q) are measured in units of joules (J). On the right side, (units of mass)(units of temperature change)(units of specific heat) = kg × °C × J/(kg ·°C) = J. The units on both sides of the equation match.
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Temperature, Thermal Energy, and Heat

16. Measuring Specific Heat
The specific heat of a material can be measured using a device called a calorimeter.
In a calorimeter, a heated sample transfers thermal energy to a known mass of water.
The energy absorbed by the water can be calculated by measuring the water’s temperature change.
The thermal energy released by the sample equals the thermal energy absorbed by the water.
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Temperature, Thermal Energy, and Heat

17. Review Essential Questions Vocabulary What is temperature?
How are thermal energy and temperature related?
What is the difference between thermal energy and heat?
Vocabulary
temperature
thermal energy
heat
specific heat
Temperature, Thermal Energy, and Heat
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