Energy Changes and Transfers

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Questions and Answers

How does our energy change as we walk?

Our energy changes as we walk because we convert chemical energy stored in our muscles into kinetic energy to move our body. This energy is also used to overcome friction and lift our weight.

Name as many energy stores as you can?

Gravitational (correct)
Electrostatic (correct)
Magnetic (correct)
Elastic Potential (correct)
Thermal (Internal) (correct)
Kinetic (correct)
Chemical (correct)
Nuclear (correct)

Match the different energy stores to their definitions:

Kinetic = Energy possessed by an object due to its motion Magnetic = Energy stored in the magnetic field around a magnet Elastic Potential = Energy stored in a stretched or compressed object Thermal (Internal) = Energy relating to the temperature of an object Electrostatic = Energy stored as a result of electric charges Nuclear = Energy released by processes within the nucleus of an atom Gravitational = Energy possessed by an object due to its position in a gravitational field Chemical = Energy stored in the bonds of molecules

Energy can be transferred from one store to another. This happens in ______ ways.

four Signup and view all the answers

Energy transfers::

By An Electric Current (A), By Heating (B), By A Force (C), By Waves (eg. light or sound) also called Radiation (D) Signup and view all the answers

Describe the energy changes that take place when a ball is dropped from a height.

When a ball is dropped from a height, it starts with gravitational potential energy due to its position above the ground. As the ball falls, this gravitational potential energy is converted into kinetic energy, the energy of motion. At the moment of impact, the ball's kinetic energy is transferred to the ground, causing a change in its thermal energy (heat) and generating sound. Signup and view all the answers

Where is the energy stored when the ball is high up?

Gravitational (D) Signup and view all the answers

Where is the energy stored as the ball moves faster?

Kinetic (A) Signup and view all the answers

Which pathway?

Gravitational Potential Energy Store -> Kinetic Energy Store (D) Signup and view all the answers

Does all the gravitational energy turn into kinetic energy?

No (B) Signup and view all the answers

What energy is wasted?

Some of the gravitational potential energy is wasted as heat and sound. Heat is generated due to friction between the air and the ball as it falls. Sound is produced as the ball hits the ground. Signup and view all the answers

Describe the energy changes that take place when a ball is dropped from a height. Write it as a sentence.

Energy is transferred from the gravitational energy store when the ball is high up to the kinetic energy store as the ball falls by the force of weight. Signup and view all the answers

When a stretched rubber band is released, it moves across the room. ? store ? store Which pathway?

Elastic potential energy store Kinetic energy store Elastic Potential Energy Store -> Kinetic Energy Store Signup and view all the answers

When a stretched rubber band is released, it moves across the room. Energy is transferred from the elastic potential energy store when the rubber band is released... ...to the kinetic store as the rubber band moves Elastic potential energy store Kinetic energy store By a force As a sentence?

Energy is transferred from the elastic potential energy store to the kinetic energy store as the rubber band moves. Signup and view all the answers

We can show energy transfers in a diagram: ??? ??? Challenge: what are the names of the stores and transfers?

The diagram should represent the energy transformations involving the relevant energy stores. It should illustrate the flow of energy and the specific pathways involved. The challenge is to determine the names of the stores, such as gravitational potential, and transfers, such as by wave or by force. Signup and view all the answers

What situation does this diagram represent?

The diagram represents energy transformations that occur in a specific situation, which needs to be identified based on the information provided in the diagram. Understanding the energy stores and transfers depicted in the diagram will help you understand what the situation is. Signup and view all the answers

Challenge: is this lamp efficient? Justify your answer.

The efficiency of the lamp depends on the amount of energy converted into useful light energy compared to the energy wasted as heat. A more efficient lamp converts more energy into light and less into heat. Justification requires analyzing the energy stores shown in the diagram and the proportions of energy transferred to each store. Signup and view all the answers

Where is the energy stored before the candle starts burning?

The chemical energy store (C) Signup and view all the answers

As the candle burns, the air gets warmer. Where has the energy from the chemical energy store of the candle been transferred to?

The thermal energy store of the air (B) Signup and view all the answers

How is the energy transferred from the chemical energy store of the candle, to the thermal energy store of the air?

By heating (C) Signup and view all the answers

A battery-powered drone is flown upwards at a steady speed. Which energy store increases?

Gravitational Potential (A) Signup and view all the answers

Task: Describe the changes in energy when:

A ball is thrown upwards

Water is boiled in an electric kettle

A battery-powered torch is turned on.

<ol> <li>When a ball is thrown upwards, its kinetic energy is increased as it moves upwards. However, the ball also gains gravitational potential energy due to its increasing height. As the ball reaches its peak, its kinetic energy decreases, while its gravitational potential energy reaches its maximum. Then, the ball falls back down, converting potential energy back to kinetic energy.</li> <li>When water is boiled in an electric kettle, electrical energy from the power source is transferred into thermal energy, which is used to increase water's temperature. This process continues until the water reaches its boiling point and transforms into a gaseous state (steam). The heat energy is lost to the environment as well.</li> <li>When a battery-powered torch is turned on, chemical energy stored in the battery is converted into electrical energy. This electrical energy is then transferred into light energy. In addition, some electrical energy is also converted into heat energy, which tends to be considered lost energy.</li> </ol> Signup and view all the answers

Challenge:

Where is energy stored in your muscles?

Explain using energy stores why a chocolate bar is better to eat before a race than an apple.

Describe the energy changes when you eat a chocolate bar and run a race.

<ol> <li>Energy is stored in muscles in the form of chemical energy within the muscle fibers. This energy comes from the chemical bonds of molecules like glycogen. The bonds hold potential energy, which can be released to perform work.</li> <li>A chocolate bar provides a greater concentration of chemical energy compared to an apple. It has a higher amount of carbohydrates and fats, which have a greater energy density. Your body utilizes the chemical energy stored in carbohydrates and fats to produce the energy needed to run. Therefore, a chocolate bar provides a more concentrated energy source, making it a better choice for a race.</li> <li>When you eat a chocolate bar, your digestive system breaks down the carbohydrates and fats, releasing their chemical energy. This energy is then absorbed into your bloodstream and transported to your muscles. Once the energy reaches your muscles, it is converted into chemical energy for storage within the muscle fibers. When you run, your body uses this stored chemical energy to power the contraction of muscle fibers, converting it into kinetic energy. Additionally, your body generates heat during the process, which is an example of energy loss.</li> </ol> Signup and view all the answers

Without looking back at your book, sort these into energy stores and energy transfers

This question encourages students to review the concept of energy stores and transfers without relying on their notes. It promotes memory retention and the development of a conceptual understanding of these fundamental principles. Students are expected to come up with a list of energy stores, like kinetic, potential, and thermal, and energy transfers such as heating, electrical currents, waves, and forces. Signup and view all the answers

Flashcards

What is energy?

The ability to do work or cause change.

Energy transfer

The movement of energy from one store to another.