ENERGY. What is energy? Energy is the capacity to do work or to produce heat.

ENERGY

What is energy?

Energy is the capacity to do work

or to produce heat.

Forms of Energy

Energy comes in many forms, but they can beconveniently classified into three categories.

Radiant Energy

Kinetic Energy

Potential Energy

What is radiant energy?

Radiant energy is energy given off by thesun that can travel through empty space.

Examples of Radiant Energy

Visible light

X-rays

Radio waves

What is kinetic energy (KE)?

Kinetic energy is energy in motion.

Types of kinetic energy

Mechanical energyEXAMPLE: a moving car

Thermal (or heat) energyEXAMPLE: boiling a pot of water

What is potential energy (PE)?

Potential energy is stored energy.

Types of potential energy

Gravitational potential energyEXAMPLE:

Electrical energyEXAMPLE:

Types of potential energy

Chemical energyEXAMPLE:

Law of Conservation of Energy

The law of conservation of energy states that energy is

neither created nor destroyed. It can betransformed from one kind of energy into

another.

Energy Transformation

Modern civilization is possiblebecause we have learned how tochange energy from one form toanother and use it to do work forus and to live more comfortably.

SOURCES OF ENERGY

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 1°C

c.) Joule (J) SI unit of energy (1 cal = 4.184 J)

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)

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)

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)

Practice Problems

c. 20 kilocalories joules

20,000 cal

d. 2.4 kilojoules calories

2,400 J

DO NOW: Energy Concept Map

ENERGY

Energy Transformations

Burning gas to drive a car

chemical thermal mechanical

2.1 Review and ReinforcementCalorie and Joule Conversions

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

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

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