CAPT REVIEW: Energy Transformations

STRAND I

Part I: States of Matter

All matter is composed of tiny particles (atoms and molecules) that are in constant motion. The amount of kinetic (motion) energy and attraction between these particles determines the state of matter of the substance- solid, liquid, or gas.

The particles in a solid

  • are close together
  • are in an rigid, orderly arrangement
  • are strongly attracted to each other
  • vibrate in a set position
  • have the least amount of energy of all three states of matter

The particles in a liquid

  • are fairly close together, but farther apart than solids
  • have some attraction to each other
  • can move and flow over each other
  • have more energy than solids, but less than gases

The particles in a gas

  • are very far apart
  • have almost no attraction to each other
  • move around very quickly in all directions
  • have the greatest amount of energy of all three states of matter

**Temperature measures the average kinetic (motion) energy of the particles in a substance.
A phase changeor change of state occurs when a substance changes from one state of matter into another. This process occurs in two ways:

  1. By adding energy to the particles in the substance
  • By adding energy (heating a substance) the particles will increase their motion.
  • If enough energy is added, the particles can overcome the attractive forces holding them together and change into another state of matter with a higher energy.
  • This occurs in melting (solid to liquid), boiling/ vaporization (liquid to gas), and sublimation (solid to gas).
  1. By removing energy from the particles in a substance
  • By removing energy (cooling a substance) the particles will decrease their motion
  • If enough energy is removed the particles will slow down and the attractive forces between particles will hold them closer together in a state of matter with lower energy.
  • This occurs in freezing (liquid to solid), condensation (gas to liquid), and deposition (gas to solid).

Part II: Forms of Energy

Energy is the ability to do work and cause change. Energy can exist is many different forms.

  • Kinetic energy- energy of motion
  • Potential energy- energy stored in an object with the potential to do work
  • Gravitational Potential energy- energy stored in an object due to its position above the ground
  • Elastic Potential energy- energy stored in an object that is stretched or compressed
  • Mechanical energy- energy associated with the motion of everyday objects (things you can see, not on an atomic level)
  • Thermal energy- energy associated with the motion of particles; related to the temperature of the substance
  • Chemical energy- energy stored in the chemical bonds of a substance such as in fuel, food, and batteries
  • Electrical energy- energy associated with the movement of electrical charges
  • Electromagnetic (radiant) energy- energy that travels in the form of waves such as visible light, radio waves, and x rays
  • Nuclear energy- energy stored in the nucleus (center) of an atom; this is the energy used to power the sun and used in Nuclear power plants

Energy Transformation

The Law of Conservation of Energy states that energy cannot be created nor destroyed. However, energy can be converted from one form to another.

Heat Transfer

Heat (thermal energy) flows from warmer objects to cooler objects. There are three methods of heat transfer- conduction, convection, and radiation.

Conduction

Transfer of heat within a material or between 2 materials that are touching each other. Particles that are in warmer objects are moving around faster than particles in cooler objects. The “hot” particles “bump” into the “cooler” objects and transfer the energy to the cooler ones warming them up.

Radiation

Transfer of thermal (heat) energy through electromagnetic waves such as heat or light.

Convection

Similar to conduction, but refers to the transfer of energy through a fluid (a liquid or a gas). The example above shows water at the bottom of the pot heating up. This water then becomes less dense as it warms and rises to the top of the pot. The cooler water at the top of the pot is then pushed down by the warm water as indicated by the arrows. This is referred to as convection current. Another example is how a wood stove fireplace can heat a room. Warm air rises through convection and creates a convection current that circulates the air in the room.

Electricity is a form of energy caused by moving electrical charges.

Static Electricity

When you rub a balloon on your hair, electrons are transferred from your hair to the balloon. Your head becomes net positively charged. The balloon has a net negative charge. The balloon is attracted to the wall.

Electric Energy

There are three characteristics of an electrical circuit- voltage (V), current (I), and resistance (R).

Voltage (or potential difference) is the amount of “push” on the electrons in the circuit. This is provided by electricity source (battery or outlet). The unit of voltage is volts.

Current is a measure of the amount of electrical charge that is flowing through the circuit. The unit of current is ampere or amp.

Resistance is a measure of how hard it is for the electron to flow through the circuit. The unit of resistance is ohm.

Magnetism

The magnetic force is a force magnet exerts on another magnet or magnetic material. All magnets have two poles or ends called a north pole and a south pole. These poles will attract or repel other magnetic poles. Like poles repel and opposite poles attract. The area around a magnet where the magnetic forces interact is known as the magnetic field. Certain materials such as iron, nickel, and cobalt have strong magnetic fields. These substances can form permanent magnets. Some materials with a weak magnetic field can form temporary magnets.

Electromagnetism

Electricity and Magnetism are related in a single force known as the electromagnetic force. Moving electric charges (a current) can create a magnetic field. An electric current can be used to produce a temporary magnet known as an electromagnet. This is done by taking a current-carrying wire and coiling it around an object that can be magnetized (like an iron nail).

The strength of this electromagnet can be increased by increasing the number of coils or increasing the current in the wire.

Generation of Electricity

Generators can be turned using fossil or nuclear fuels. The heat from the fuel boils water to make steam, which expands and pushes against the blades of a turbine. The spinning turbine then turns the generator.

To the left is a diagram for the generation of electricity from a fossil fuel such as natural gas, using steam to drive the turbines.

1: The heat from the burning fuel turns water into steam in the boilers.

2: The steam drives the turbines

3: The turbines spin the generators, which produce the electricity.

4: The electricity goes to the transformers, which produce the correct voltage for transmission.

Comparing Renewable and Nonrenewable Energy Sources

Energy Source / Advantages / Disadvantages
Nonrenewable
Ex. Coal, oil, natural gas, nuclear power /
  • Cheap
  • Easy to use
/
  • Cannot be easily replaced
  • Pollution caused by burning these items- carbon dioxide, smog, greenhouse effect
  • Nuclear waste is difficult to dispose of

Renewable
Ex. Solar, wind, hydroelectric, geothermal /
  • Energy source will not run out
  • Energy source is clean and does not produce carbon dioxide
/
  • Expensive to set up
  • More research needs to be done to make it something that could be used by everyone

Practice Questions (answers are at the end)

  1. Which graph best shows the relationship between the temperature of a substance and the motion of the particles in the substance when it is heated?
  1. A burning match involves the transformation of
  2. Chemical energy to light and sound energy
  3. chemical energy to light and heat energy
  4. chemical energy to heat energy only
  5. heat energy to light energy only
  1. To demonstrate static electricity, a teacher takes an inflated rubber balloon and rubs it on her head. The rubbed balloon picks up electrons from her hair which causes her hair to have a(n)
  2. Electrical current
  3. Net positive charge
  4. Net negative charge
  5. Buildup of magnetic energy
  1. What happens to water molecules in a pool as they absorb energy?
  2. The molecules occupy less volume
  3. The molecules begin to move more slowly
  4. The kinetic energy of the atoms decreases
  5. The rate of collisions between the molecules increases
  1. What type of heat transfer is used to heat water in the recreation center pool in the question above?
  2. Conduction
  3. Convection
  4. Radiation
  5. Chemical
  1. What is the major advantage of using wind energy instead of coal or nuclear power plants?
  2. Wind is a renewable energy resource
  3. Wind is consistently available in all locations
  4. Windmills reduce the strength of severe storms
  5. One windmill can produce more energy than a nuclear power plant
  1. A student constructed an electromagnet that was capable of attractingand picking up 6 paperclips. The student wants to change theelectromagnet to pick up more than 6 paperclips. Which of the following would be the best adjustment to make to improve the electromagnet?
  2. Replace the nail with a wooden pencil
  3. Increase the number of loops around the nail from 15 to 25
  4. Decrease the current flowing through the wire from 2 amps to 1 amp
  5. Use a wire with a larger resistance
  1. Which of the following best represents the energy transfer that occurs when an incandescent light bulb is turned on?
  2. Chemical energy → thermal energy →kinetic energy
  3. Electrical energy → electromagnetic energy → chemical energy
  4. Gravitational energy → thermal energy → chemical energy
  5. Electrical energy → thermal energy → electromagnetic energy
  1. If a 9-V battery is replaced with a 12-V battery in an electrical circuit containing a light bulb, which of the following changes would you expect to occur?
  2. The resistance in the circuit will decrease
  3. The current in the circuit will increase
  4. The light bulb will become dimmer
  5. Nothing in the circuit will be affected

Answers:

1. A

2. B

3. B

4. D

5. B

6. A

7. B

8. D

9. B

Name ______Date ______Period ______

INTRODUCTION QUESTIONS:

  1. What are fossil fuels? Give 3 examples.

______

  1. What are alternative sources of energy?

______

  1. What is the difference between renewable and nonrenewable resources?

______

  1. Why do we need to seek out alternative forms of energy?

______

BACKGROUND:

Most people in the United States use an electric stove or a natural gas stove to cook their food. This is not the case in much of the world. Approximately 50% of the people on Earth cook using fire from burning wood.

One alternative to cooking with wood is using solar cookers. These devices use energy from the sun to cook food without producing any pollution. While there are many designs for solar cookers, a simple solar cooker can be made from everyday materials.

SCENARIO:

A group of students conducted an experiment to determine how the design of a solar cooker affected the temperature of water. The procedure and data collected from different groups in the class is found below.

Question 1:

Student A made his solar cooker from a cardboard box with four flaps. The flaps of the box were angled up at a 45º angle and covered in aluminum foil. A plastic, uncovered container holding 150 mL of water was covered in black paint and placed in the center of the box. The student measured the initial temperature of the water, and after a 15 minute period of sun exposure, he measured the final temperature as well.

Student B also made a solar cooker from the same size cardboard box, but he angled his four flaps at a 90º angle and covered them in black paint. He placed the same size plastic, uncovered container holding 150 mL of water covered in black paint in the center of the box. He also measured the initial temperature of the water and after a 15 minute period of sun exposure, he measured the final temperature as well.

  1. Describe the similarities and differences between the two student’s solar cooker designs.

______

  1. Student A and B compared their results, can they draw a valid conclusion based on the results they obtained? Explain.

______

Question 2:

Student C’s procedure is shown below.

  1. Obtain a cardboard box with four flaps.
  2. Cover the four flaps with foil.
  3. Cover the bottom of the box with black paper.
  4. Place a glass beaker with 100 mL of water in the bottom of the box.
  5. Measure the initial temperature of the water.
  6. Place the solar cooker under a heat lamp for 30 minutes.
  7. Measure the final temperature of the water.
  8. Repeat steps 3-7 replacing the black paper with white, green, red, and no paper.
  1. Identify the independent and dependent variables of the experiment.

______

  1. What is the purpose of running a trial with no paper covering the bottom of the box? Explain your answer.

______

Question 3:

Student D (from Ecuador- near the equator) and Student E (from Canada- north of the United States) conducted an experiment to determine the effect of the angle of the panels of their solar cooker. Both students obtained the same standard solar cooker. Each student conducted their experiment on October 1st at noon and left their solar cooker out on a sunny day for 30 minutes. A graph of each student’s data is found below:

  1. Based on the data, which angle is the most effective to use to raise the temperature of water? Support your answer using data from the graph.

______

  1. Explain why the data from student D and student E differs.

______

Question 4:

The source of energy for California’s electricity has varied from 1975 to 2005. The graph below represents the use of petroleum, biomass, and wind energy in California from this time period.

  1. Describe the trends of the three sources of energy used in California over the past 30 years.

______

  1. What type of energy source (renewable or nonrenewable) was California most dependent on in 1985?

______

  1. Do you believe that California’s changing dependence on energy sources as shown on the graph will have a positive or negative impact? Support your answer with specific examples.

______

  1. What do you predict will happen to the use of biomass over the next 10 years? Explain your answer.

______

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