# Energy

## GRADE

Forms of Energy

You have heard of the word "energy" all your life.. You need to eat vegetables to grow strong and have "energy". You need to go to bed early so you will have "energy" in the morning to go to school. Energy is the ability to do work. Energy is everywhere in nature-sunlight, wind, water, plants, and animals. We use energy everyday.

Two kinds of energy are kinetic and potential. Kinetic energy is the energy of motion. Potential energy is stored energy. A good example of kinetic and potential energy is a frog leaping. A frog sitting on a lily pad is an example of potential energy. The frog leaping is an example of kinetic energy.

Different forms of energy are

• light
• chemical
• mechanical
• heat
• electric
• atomic
• sound

All these forms of energy can be broken down either into kinetic or potential.

Law of Conservation of Energy- Energy can neither be created nor destroyed. Energy is always changing from one kind to another. The total energy of an object never changes.

Potential energy + Kinetic energy = Total energy and Total energy - Kinetic energy = Potential energy and Total energy - Potential energy = Kinetic energy

All three equations are the same.

(narrative and pictorial description of potential and kinetic energy, use math)

Energy of Reactions

All chemical reactions require energy to occur. The rate of a reaction or how fast it occurs depends on:

• the number of particles,
• the temperature, and
• the presence of any catalysts.

1. PARTICLE CONCENTRATION

If you add more soap to water, the more bubbles will form. The higher the concentration of particles in a reaction, the faster it will go. Concentration is the number of particles in a volume of space. Look at the boxes below, which one will the reaction occur faster.

2. TEMPERATURE

Temperature is an indicator of heat. If you want your water to boil faster, you increase the temperature by turning the knob on high. Most reactions go faster at higher temperatures. Remember the difference between water vapor particles and ice particles. Water vapor particles move about more rapidly then ice particles. Ice particles are moving in slow motion compared to the gas particles. (animation)

3. CATALYSTS

Catalysts are substances that help make a reaction go faster. Scientists believe adding a catalyst to a reaction increases the number of particle collisions. A collision is when something hits something else with great energy. Some examples of catalysts are enzymes. There are enzymes in your mouth that help speed up the procees of digestion.

Energy and chemical reactions

Chemical reactions require energy. This energy can either be released or absorbed. Chemical reactions that give up heat energy are called exothermic reactions. The prefix "exo" means "out" and "therm" means "heat". Burning wood in a fireplace gives off heat to warm you up. Most chemical reactions are exothermic. Endothermic reactions absorb heat. "Endo" means "in" and "thermic" means "heat". Baking powder in dough causes bread to rise. It absorbs the heat from the oven to form carbon dioxide gas.

to Chapter 4- Measuring Energy

Pages and gif animations written and designed by Sheila M. Estacio. Please send comments, praises, gripes, questions to sme2446@is2.nyu.edu