Vernier Software & Technology

# What is Energy?

## Introduction

Energy is defined as the ability to do work. Energy makes it possible to do most things, from baking cookies to hitting a ball with a bat.

There are two broad categories of energy: potential and kinetic. Potential energy is energy that is stored. Forms of potential energy include chemical, gravitational, elastic, and nuclear. Kinetic energy is the energy of motion. Electrical, radiant, thermal, and sound energy are all examples of kinetic energy.

We use electrical energy to do work for us like power a computer and heat our homes. How much energy does it take to do these things? To answer that question, we need to know where the energy comes from. Most electrical energy in the United States is generated from fossil fuels such as natural gas and coal. While all of these fuel sources are forms of potential energy, they do not necessarily contain the same amount of energy per volume. To make it more complicated, all these different fuels are sold in different units of volume!

In order to be able to compare energy sources more easily, conversion into measurements of a common unit is necessary. An accepted unit for comparison when talking about energy, especially in science, is the joule (J). In this experiment, you will determine the energy content (in J/g) of different fuels. You will do this by burning a known weight of the fuel and capturing the heat released in a known mass of water in a calorimeter. If you measure the initial and final temperatures, the energy released can be calculated using the equation

$H = \Delta t \bullet m \bullet C_{p}$

where H = heat energy absorbed (in J), Δt = change in temperature (in °C), m = mass (in g), and Cp = specific heat capacity (4.18 J/g°C for water). Dividing the resulting energy value by grams of fuel burned gives the energy content (in J/g).

## Objectives

• Explain the difference between potential and kinetic energy and give examples of both.
• Identify the units that are used to measure energy.
• Determine the energy content of fuels.

## Sensors and Equipment

This experiment features the following Vernier sensors and equipment.