Energy

Energy is measured in a couple of different ways.

One of the basic measuring blocks is called a Btu. This stands for British thermal unit.

Btu is defined as the amount of heat energy it takes to raise the temperature of one pound of water by one degree Fahrenheit, at sea level.

One Btu roughly equals:

• One average candy bar
• 4/5 of a peanut butter and jelly sandwich
• One blue-tip kitchen match
It takes, for example, about 2,000 Btus to make a pot of coffee.

Energy can also be measured in joules. Joules sounds the same way as the word jewels, like diamonds and emeralds. It takes 1,000 joules to equal a British thermal unit. So:

```         1,000 joules = 1 Btu
```
So, it would take 2 million joules to make a pot of coffee.

Joule is named after an English physicist named James Prescott Joule who lived from 1818 to 1889. He discovered that this a type of energy.

One joule is the amount of energy needed to lift one pound about nine inches.

Around the world, scientists measure energy in joules rather than Btus. It's much like people around the world using the metric system, meters and kilograms, instead of the English system of feet and pounds.

Like in the metric system, you can have kilojoules -- "kilo" means 1,000.

```        1,000 joules = 1 kilojoule = 1 Btu
```
A piece of buttered toast contains about 315 kilojoules of energy. With that energy you could:
• Jog for 6 minutes
• Bicycle for 10 minutes
• Walk briskly for 15 minutes
• Sleep for 1-1/2 hours
• Run a car for 7 seconds at about 50 miles per hour
• Light a 60 watt light bulb for 1-1/2 hours

According to the Law of Conservation of Matter and Energy, Energy can only change its form, It cannot be created nor can it be destroyed.

Here are some changes in energy from one form to another.

• Stored energy in a flashlight's batteries becomes light energy when turned on.
• Food contains energy stored as chemical potential energy. Your body uses the stored energy to do work, kinetic energy.
• If you overeat, the food's energy is stored as potential energy in fat.
• When you talk on the phone, your voice is changed to electrical energy. The phone on the other end changes the electrical energy into sound energy.
• A car uses stored chemical energy in gasoline to move. The engine changes the chemical energy into heat and kinetic energy to power the car.
• A toaster changes electrical energy into heat energy.
• A television changes electrical energy into light and sound energy.

Heat Energy

Heat is a form of energy. We use it for a lot of things like warming our homes and cooking our food.

Heat energy moves in three ways:

1. Conduction
2. Convection