Physical Science Chapter 13 Energy Physical Science Chapter 13

Nature of Energy Energy is all around us. You hear energy as sound, see energy as light, and feel energy when the wind blows. What is energy? Energy is the ability to do work. Energy is measured in joules.

Kinetic and Potential Energy Energy is the ability to do work. Energy exists in two different states: kinetic energy and potential energy. All five forms of energy can exist in either of these states.

Kinetic Energy An object that is in motion has the ability to perform work. Kinetic energy is the energy of motion. Kinetic energy depends on both mass and velocity of the object in motion. A change in either mass or velocity will affect the kinetic energy of the object. The equation for kinetic energy: K.E. = (mass x velocity2) / 2

Potential Energy Potential energy is the energy of position. If an object has the potential to do work, it has potential energy. Potential energy is the stored energy given to an object when work was done upon it. Potential energy is not always mechanical.

Gravitational Potential Energy (GPE) Gravitational potential energy (GPE) is potential energy (PE) that is dependent upon height of position. Ex. Waterfall, Diver, Snowflake Weight also affects the amount of GPE. Therefore, a change in height or weight will affect the GPE The equation for gravitational potential energy is: GPE = Weight x Height

Forms of Energy Energy appears in many forms. Five main forms of energy are: mechanical, heat, chemical, electromagnetic, and nuclear. Each form of energy can be changed or converted into one of the other energy forms by the action of work.

Mechanical Energy Matter that is in motion has energy. This energy associated with motion is called mechanical energy. Ex. Water falling, automobile driving, sound

Heat Energy All matter is made up of tiny particles called atoms that are constantly moving. Heat energy is the internal motion of the atoms. The faster the particles move, the more heat energy they have. Heat energy usually results from friction. Ex. Rub your hands together really fast, what happens? Heat energy causes changes in temperature & phase (solid, liquid, gas).

Chemical Energy Energy exists in bonds that hold atoms together, this energy is called chemical energy. When the bonds are broken, energy is released. Ex. Fire in a barbeque, digestion of food, ATP molecules in cells

Electromagnetic Energy Electromagnetic energy is the energy created by moving electric charges doing work. Power lines carry electromagnetic energy to your home in the form of electricity. Each color of light represents a different amount of electromagnetic energy. Electromagnetic waves is also carried by X-rays, radio waves and laser light.

Nuclear Energy The nucleus of an atom is the source of nuclear energy. Nuclear energy is the energy released when an atom’s nucleus is split. Nuclear energy is also released when light weight nuclei collide at high speeds and fuse. Nuclear energy is the most concentrated form of energy. Nuclear energy is what powers the sun.

Energy Conversions Energy can be transferred from one object to another or changed from one form to another. Changes in the forms of energy are called energy conversions.

Kinetic-Potential Energy Conversions One of the most common energy conversions involves the changing of potential energy (PE) to kinetic energy (KE) or kinetic energy to potential energy. Ex. Pulling a bow, or throwing a ball up in the air.

Other Conversions All forms of energy can be converted into other forms of energy. Ex. Green plants convert solar energy into chemical energy Heat engine coverts heat into mechanical energy

Conservation of Energy Scientists have found that energy is converted from one form to another with no net loss. The law of conservation of energy states, “that energy can neither be created nor destroyed by ordinary means.” The law of conservation of energy is one of the fundamentals of science.

Albert Einstein Einstein showed that even the tiniest mass can form a tremendous amount of energy. He found that mass and energy can be converted into one another. Einstein showed that if matter is destroyed, energy is created & if energy is destroyed, matter is created. The relationship was summed up in a simple equation: E = mc2