Chapter 7: Energy & Energy Transformations Week 1 Chapter 7: Energy & Energy Transformations

Other Forms of Energy March 28

Today’s Objectives Students will be able to: Explain how kinetic and potential energy relate to other forms of energy. Describe how work can be done by different forms of energy.

Bellringer So far we have been using the words kinetic and potential to talk about energy. Are there other types of energy? Which ones have you heard of?

Law of Conservation of Energy March 29

Today’s Objectives Students will be able to: Explain the law of conservation of energy in their own words. Describe how friction affects energy.

Bellringer Rub your hands together quickly. Stop rubbing and immediately shake hands with another student. Bellringer questions: What type of energy did you demonstrate? Where did this energy come from?

Changes Between Forms of Energy What did the items represent? When you exchanged an item, was that item gone forever? How did this activity demonstrate how energy is transferred?

The Law of Conservation of Energy According to the law of conservation of energy, energy can be transformed from one form into another or transferred from one region to another, but energy cannot be created or destroyed. What type of energy were you using when you were rubbing your hands together earlier? What happened to that energy?

Friction Friction is a force that resists the sliding of one surface over another. There is always some friction between any surfaces that are in contact with each other. Friction can cause some work done to change to thermal energy. For example, as you pedal a bicycle, you do work and transfer energy to the bicycle. When you apply brakes on a bicycle, the bicycle’s mechanical energy is not destroyed.

The first three bars are filled in The first three bars are filled in. On the back of your worksheet, fill the bars for the next two images according to how much of each energy you think would be involved.

Friction Because of friction, between moving parts of a bicycle, some of the work you do changes to thermal energy. When you apply brakes on a bicycle, the bicycle’s mechanical energy is not destroyed. The bicycle’s mechanical energy is transformed into thermal energy. The total amount of energy remains the same.

In groups of two, think of an example that demonstrates the law of conservation of energy using three forms of energy that we learned about yesterday.

Thermal Energy March 31 and April 1

Today’s Objectives Students will be able to: Describe the transfer of thermal energy. Identify a transfer of thermal energy as conduction, convection, or radiation. Calculate the rate of temperature change.

Bellringer #3: Mixing Water Melinda filled two glasses of equal size half-full with water. The water in one glass was 50 degrees Celsius. The water in the other glass was 10 degrees Celsius. She poured one glass into the other, stirred the liquid, and measured the temperature of the full glass of water. What do you think the temperature of the full glass would be after the water was mixed? Select a prediction and explain your reasoning. A. 20 degrees Celsius B. 30 degrees Celsius C. 40 degrees Celsius D. 50 degrees Celsius E. 60 degrees Celsius

Bellringer #4 Select an answer and explain your reasoning.

Heat What is heat? Recall: What is thermal energy? How is it different from thermal energy? Heat is thermal energy moving from a region of higher temperature to a region of lower temperature. Objects contain thermal energy, not heat. Heat is the transfer of thermal energy to the air or another object. NOT destroyed. Thermal energy is caused by the random motion of particles in an object. It is the sum of kinetic and potential energies of these particles. Heat is the transfer of thermal energy .

Temperature The movement of thermal energy causes changes in temperature. Can an object with a low temperature have thermal energy? Identify the areas of warmer and cooler temperatures in the image. Two objects in contact with each other at the same temperature are said to be in thermal equilibrium. Thermal energy is transferred from high temperature to low temperature until thermal equilibrium is reached. 1. Yes, all matter contains moving particles that have kinetic energy. 2. Warmer: soup, cooler: air around soup

Conduction Thermal energy can be transferred by different processes. Conduction is the transfer of thermal energy due to collisions between particles in matter. How would you know when thermal energy is being transferred by conduction? When faster-moving particles collide with nearby particles at slower speeds, thermal energy is transferred. Conduction occurs in solids, liquids, and gases. Solids are better thermal conductors than liquids and gases. A material in which thermal energy moves quickly is called a thermal conductor. Most metals are excellent thermal conductors. 1. Direct contact

Convection Convection is the transfer of thermal energy by the movement of particles from one part of a material to another. What state of matter does convection occur in? Convection occurs in liquids and gases. What initiates the convection process? Convection begins when part of a liquid or gas becomes warmer than the rest of it. Why does warm water rise to the surface? The cooler, denser liquid or gas falls, pushing the warmer, less dense liquid or gas to the top. How is convection different from conduction? 4. Energy is transferred by the mass movement of molecules

Radiation Radiation is the transfer of thermal energy from one object to another by electromagnetic waves. Radiation transfers thermal energy through matter or through space, where no matter exists. How is transfer of thermal energy by radiation different from convection and conduction? Thermal energy transfer by radiation occurs between objects that are not in contact. Does an object have to give off visible light in order to radiate heat? All objects give off electromagnetic waves, but most are not visible. Extremely hot objects emit visible light. Electromagnetic waves carry energy and radiation transfers this thermal energy from objects at higher temperatures to objects at lower temperatures. Radiation occurs by EM waves and does not require particles.

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