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Section 10.1
Energy, Temperature, and Heat
Why Do Things Happen?
Section 10.1
Energy, Temperature, and Heat
1. To understand the importance and general properties of energy
2. To understand the concepts of temperature and heat
3. To understand the direction of energy flow as heat
Objectives
Section 10.1
Energy, Temperature, and Heat
Section 10.1
Energy, Temperature, and Heat
What is Energy?
Kinetic, potential, thermal, gravitational, sound, elastic, light / electromagnetic, electrical, electrostatic energies are examples
Energy is the driver of all changes. It flows between objects, it spreads out throughout the universe and in doing so is the driver of all observable phenomena (including chemical reactions)
Section 10.1
Energy, Temperature, and Heat
• Energy is the ability to do work or produce heat.
A. The Nature of Energy
Crane Lifting
Doing Work:
Explosion
Producing Heat:
Section 10.1
Energy, Temperature, and Heat
What is the difference between potential and kinetic energy?
Section 10.1
Energy, Temperature, and Heat
• Energy is the ability to do work or produce heat.
Potential energy
Energy of position
Kinetic energy
Energy of motion
E = ½ mv2
A. The Nature of Energy
Section 10.1
Energy, Temperature, and Heat
A. The Nature of Energy
• Law of conservation of energy
– Energy can be converted from one form to another but can neither be created nor destroyed.
Bounce Ball Into Space
Section 10.1
Energy, Temperature, and Heat
A. The Nature of Energy
• Law of conservation of energy in a chemical reaction
– Energy can be converted from one form to another but can neither be created or destroyed.
– Stored chemical energy of reactants is equal to energy of products plus energy given off
– Some of the stored chemical energy of methane and oxygen is converted to heat as they react
Section 10.1
Energy, Temperature, and Heat
• Temperature is a measure of the random motions (kinetic energy) of the components of a substance.
B. Temperature and Heat
Hot water Cold water
(90. oC) (10. oC)
Fast Slow
Section 10.1
Energy, Temperature, and Heat
Measuring Temperature
Section 10.1
Energy, Temperature, and Heat
• Heat transfer is a flow of energy between two objects due to a temperature difference between the objects.– Heat transfer is the way in which thermal energy is
moved from a hot object to a colder object.
B. Temperature and Heat
Hot water Cold water
(90. oC) (10. oC)
Water Water
(50. oC) (50. oC)
Section 10.1
Energy, Temperature, and Heat
Heat Transfer
The transition of thermal energy from a hotter to a cooler body
• Radiation• Conduction• Convection• (Phase Change)
Section 10.1
Energy, Temperature, and Heat
C. Exothermic and Endothermic Processes
• System – part of the universe on which we focus attention• Surroundings – everything else in the universe
Look at the example of burning a match:
Section 10.1
Energy, Temperature, and Heat
C. Exothermic and Endothermic Processes
• Exothermic – heat energy flows out of the system
• Endothermic – heat energy flows into the system
