Law of Conserv. of Energy
Energy Transformations
Potential & Kinetic Energy
Thermal Energy
Other
100
Which statement is true according to the law of conservation of energy?
a. energy can be created
b. energy can be destroyed
c. energy can change forms
c. energy can change forms
Energy CANNOT be created or destroyed; energy CAN change forms (ex. electrical to heat)
100
What type of energy transformation takes place in hydroelectric power plants?
mechanical energy (of the moving water which moves a turbine) transforms into electrical energy.
100
Olivia is working to design a soccer ball that conserves all of its kinetic and potential energy. She drops the ball to the ground from a height of 2 meters. If it really works, how high should the ball bounce?
EXACTLY 2 meters. (We are assuming no air friction or resistance. Yeah, that's a big assumption.)
100
What happens to the kinetic energy of Mrs. Hansel's coffee when she adds an ice cube to cool it down?
Some of the kinetic energy of the coffee particles is transferred to the ice cube.
100
Why does the tile floor feel colder than the rug?
Both objects are the same temperature, but the tile floor is a good heat conductor as it moves heat rapidly away from the skin, which is warmer than air temperature. The rug is a good heat insulator (poor heat conductor) in that it impedes the flow of heat and so feels comparatively warm.
200
What happens to the total energy in a closed (or isolated) system?
The total energy is conserved (meaning it does not change.)
The energy into the system = energy out of the system.
200
There is chemical energy in the food you eat.
How much of the energy is transformed into heat, other chemical forms in your body, used to help you move, or leftover as waste or fat?
ALL of the chemical energy is transformed.
(Remember energy cannot be created or destroyed.)
200
You are at a science museum and see a pendulum in the center of the foyer. The weight of the pendulum is hanging from the middle of the ceiling by a rope. It is a children's museum so you assume you are allowed to touch the weight. While your dad is not watching you lift the weight to your height of 1.6 meters. If the kinetic and potential energy of the pendulum weight is completely conserved, what should its height be when it swings back to you?
The weight will return to the same height it was released which was 1.6 meters.
200
Maalik is doing an experiment to see how much temperature change occurs when three different substances are heated. Between the three conditions, he must control (keep the same) all of the following EXCEPT:
a. the temperature of the room
b. the amount of heat energy added to each
c. the mass of each substance
d. the type of substance
d. the type of substance
200
Which takes more thermal energy to heat:
sand or water?
It takes more thermal energy to heat water. That is why though the sun's radiant energy hits each at the same time, the water takes longer than the sand to heat up.
300
What does the term “conservation” mean in regards to energy?
Energy is not created or destroyed, the same amount is always present in some form.
300
Paul pushes a Red Bull derby car, giving it kinetic energy. When this happens, what happens to the amount of energy in Paul's arm?
Paul's arm lost energy.
300
A car is in motion when the driver applies the brakes, causing the car to stop. What happened to the kinetic energy of the moving car?
The kinetic energy was transferred to another form such as heat (when the brake pad touches the brake disc, friction between the two generates heat)
300
What is the relationship between the desired temperature increase of a substance and how much heat energy is needed?
The greater the desired temperature increase, the more heat energy you need to put into the system.
300
A can of soda with at room temperature (23 C) is placed in a refrigerator with a lower temperature. Which direction will heat energy flow?
The heat energy will flow from the soda to the refrigerator air. (warmer to cooler)
400
A parked car begins to move when the driver presses the accelerator. How is energy conserved in this situation?
The energy of the car's fuel (potential chemical energy) is changed or transferred to kinetic energy (mechanical energy).
400
What factor(s) affect the amount of energy needed to increase the temperature of a material?
mass, specific heat (or type of substance) and final temperature
400
A student is holding a pumpkin at a height of 2 meters. The pumpkin has 50 joules of potential energy and 0 joules of kinetic energy.
The pumpkin is released from that height. How much potential and kinetic energy does the pumpkin have right before it hits the ground?
The pumpkin will have 50 joules of kinetic energy and 0 joules of potential energy.
400
If a substance is measured as having a change in heat energy of -10 joules, what does that mean?
Heat energy was released into the environment. (That's what the negative number means; added energy is positive.)
400
Which substance would likely require the least amount of heat energy to raise the temperature by 20 degrees Celsius?
a. metal
b. plastic
c. wood
d. paper
a. metal (because it has better thermal conductivity and can conduct heat faster)
500
When Macy kicked a soccer ball, the ball gained energy and Macy lost energy. The amount of energy the soccer ball gained is _____________ the amount of energy that Macy lost.
equal to
500
Emma is heating three pots of water on the stove. Each pot is the same size, material, and is set to the same heating level. Each pot has a different amount of water. Which pan of water will take the least energy to bring to a boil?
The pot with the smallest amount of water will take the least amount of energy to boil.
500
Mrs. Hansel lifts up her coffee cup and places it on the front demonstration table. The cup gained gravitational potential energy. Where did this energy come from?
The energy the cup now has (gravitational potential energy) came from the work Mrs. Hansel put into the cup lifting it onto the table.
500
What unit is used to measure transferred heat energy?
Joules (J) or calories
500
The ____________ the mass of a substance the ___________ energy is needed to raise the substance’s temperature.
a. higher, more
b. higher, less
c. lower, more
a. The higher the mass of a substance the more energy is needed to raise the substance's temperature.