BC Science Connections 10 Unit 3: Energy is conserved and its transformation affects living things and the environment.

Topic 3.1: What is energy? Defining energy is difficult because it cannot be observed directly. Consider a scene like this: Energy is present in many forms here – in the air, a walk down the street, in the traffic lights, the bus, and even in a conversation. But it cannot be seen.

Before we talk about energy… In order to discuss energy, we must first define work. Work is done whenever a force makes an object move. For example: You carrying your bag to school A car’s engine making the car go forward A crane lifting a steel beam

Every machine needs fuel to operate: A car needs gas You need to eat food Energy is defined as the ability to do work. Each time work is done, energy is transferred from the object doing the work to the object being worked on. So work is also the transfer of energy.

Scientists can only investigate energy indirectly because it is invisible. They do so by observing the effects energy has on other things. They have found that energy have these 4 properties: Energy can cause change in a system There are different forms of energy, with different characteristics These forms of energy can be transferred or transformed Different physical quantities contribute to different forms of energy

Anything that is under observation can be considered as a system. Defined by the observer Everything else is considered as surroundings. Therefore, Universe = system + surroundings

Types of Energy At the simplest level, energy may be classified as either: Kinetic energy (KE): the energy of motion Potential energy (PE): the stored energy of an object as a result of its condition or its position

Types of kinetic energy: (Mechanical) *kinetic energy: energy of an object that is moving Radiant energy: energy electromagnetic waves from an energy source Thermal energy: energy of random motion of particles in a substance p. 203 Kinetic energy

Kinetic Energy (cont’d) 4) Sound energy: energy of vibrations of particles 5) Electrical kinetic energy: energy of electrons moving along a wire p. 203 Kinetic energy

Types of potential energy: 1) Gravitational potential energy: energy due to the position of an object 2) Chemical potential energy: energy stored in chemical bonds p. 204 Potential energy

Potential Energy (cont’d) 3) Elastic potential energy: energy stored in a stretched or compressed object 4) Nuclear energy: energy stored in the nucleus of an atom pp. 204 and 205 Potential energy

Potential Energy (cont’d) 5) Electrical potential energy: energy stored in batteries, separated by a positive and negative charges 6) Magnetic potential energy: energy stored in a magnetic field p. 205 Potential energy

Energy can be transferred or transformed. No matter what happens within a system, the total amount of energy present before energy is transferred or transformed is always exactly equal to the total amount of energy afterwards. In other words, energy is neither created nor destroyed. This is known as the Law of conservation of energy. When energy is transferred, it stays in the same form. When energy is transformed, it changes into a different form.

Energy Transformation Energy transformation is done in order to accomplish a task. However, no energy transformation is 100% efficient because some of the energy being transformed becomes unusable. Figure 3.5: Energy is both transformed and transferred in this image, but it is never destroyed. The result is that a useful task is carried out.

Consider this mountain biker. What type of energy does it have? When will the mountain biker have the most kinetic energy? When will it have the most potential energy?