ENERGY

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ENERGY
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What is energy?

• Energy is the capacity to do work
• or to produce heat.

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Forms of Energy

• Energy comes in many forms, but they can be
• conveniently classified into three categories.
• Radiant Energy
• Kinetic Energy
• Potential Energy

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What is radiant energy?

• Radiant energy is energy given off by the
• sun that can travel through empty space.

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Examples of Radiant Energy

• Visible light
• X-rays
• Radio waves

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What is kinetic energy (KE)?

• Kinetic energy is energy in motion.

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Types of kinetic energy

• Mechanical energy
• EXAMPLE a moving car
• Thermal (or heat) energy
• EXAMPLE boiling a pot of water

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What is potential energy (PE)?

• Potential energy is stored energy.

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Types of potential energy

• Gravitational potential energy
• EXAMPLE
• Electrical energy
• EXAMPLE

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Types of potential energy

• Chemical energy
• EXAMPLE

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Law of Conservation of Energy

• The law of conservation of energy states that
  energy is
• neither created nor destroyed. It can be
• transformed from one kind of energy into another.

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Energy Transformation

• Modern civilization is possible
• because we have learned how to
• change energy from one form to
• another and use it to do work for
• us and to live more comfortably.

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SOURCES OF ENERGY
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Measuring Energy

• Energy can be measured using
• a.) Calorie (C) ? the energy stored in food
• b.) calorie (cal) ? the amount of heat needed to
  raise the temperature of 1g of water x 1C
• c.) Joule (J) ? SI unit of energy (1 cal 4.184
  J)

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Practice Problems

• Conversion between calories and joules ( 1 cal
  4.184 J)
• 1.If a container of water absorbs 25 calories of
  energy, how many joules of energy did the water
  absorb? (cal ? J)
• (1 cal 4.184 J)

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• 2.If a container of water absorbs 400 joules of
  energy, how many calories of heat did the
  water absorb? (J ? cal)
• (1 cal 4.184 J)

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• 3.Suppose you use 135 cal of energy to perform a
  task. How many joules have you used? (cal ? J)
• (1 cal 4.184 J)

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Practice Problems

• c. 20 kilocalories ? joules
• 20,000 cal

• d. 2.4 kilojoules ?calories
• 2,400 J

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DO NOW Energy Concept Map
ENERGY
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Energy Transformations

• Burning gas to drive a car

chemical
thermal
mechanical
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2.1 Review and ReinforcementCalorie and Joule
Conversions

• 14. Convert 5.42 calories and joules. (1 cal
  4.184 J)

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• Convert 726.030 calories to kilojoules.
• (1 cal 4.184 J)

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• 16. Convert 60.5 J to calories. (1 cal 4.184 J)