Energy Transformations, Conservation & Dissipation — Practice · Grade 6 Science

Chapter: Energy, Heat & Thermal Design

What this practice covers

By the end of Energy Transformations, Conservation & Dissipation you should be able to:

8 questions, written answer and multiple choice, each with a worked explanation.

Vocabulary used: conservation of energy, dissipation, evidence, system boundary, uncertainty.

Problem 1

Does stopping mean all energy vanished?
Answer and explanation

No. The energy formerly associated with the motion is transferred or redistributed into other changes and surroundings.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 2

Why is the cup alone not a closed energy account?
Answer and explanation

Energy crosses its boundary to the surroundings. The total account must include that transfer or a larger system.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 3

Could thermal output be useful in a different device?
Answer and explanation

Yes. Usefulness depends on the intended function; conservation is not a judgment about whether the output is desirable.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 4

Can the missing 10 J be declared destroyed?
Answer and explanation

No. Check omitted pathways, stored changes, and measurement uncertainty. The record is incomplete under its stated account.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 5

Develop a complete response: Calculate each light fraction and explain a limited recommendation for reading. Include relevant evidence and one method or model limit.
Answer and explanation

A gives 24 ÷ 120 = 20% as visible light and 96 J in thermal pathways. B gives 30% as visible light and 84 J in thermal pathways. B has a larger modeled light fraction for this purpose, but brightness at the page, price, lifetime, and actual measurements would also matter. Both conserve the stated input energy.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 6

Apply the unit independently: A bicycle slows with friction. What larger system would make the account clearer? Give a reason and a relevant qualification.
Answer and explanation

Include the bicycle, contact surfaces, and surrounding air, or list their energy exchanges. Reduced kinetic energy can become thermal changes and sound without being destroyed.

Compare the scientific meaning and reasoning after an independent attempt. A different accurate supported response can be correct; human review is required.

Problem 7

Which statement correctly uses conservation of energy in Energy Transformations, Conservation & Dissipation?
  1. One illustrative result establishes every real condition and needs no further evidence.
  2. Energy that is less useful has been destroyed.
  3. Conservation means every individual object must keep the same energy.
  4. conservation of energy: Energy remains accounted for across a complete system and its transfers.
Answer and explanation

conservation of energy: Energy remains accounted for across a complete system and its transfers.

Energy remains accounted for across a complete system and its transfers. A gives 24 ÷ 120 = 20% as visible light and 96 J in thermal pathways. B gives 30% as visible light and 84 J in thermal pathways. B has a larger modeled light fraction for this purpose, but brightness at the page, price, lifetime, and actual measurements would also matter. Both conserve the stated input energy.

Problem 8

Which statement correctly uses dissipation in Energy Transformations, Conservation & Dissipation?
  1. dissipation: Energy spreading into less readily useful forms or surroundings for the chosen purpose.
  2. Energy that is less useful has been destroyed.
  3. Conservation means every individual object must keep the same energy.
  4. One illustrative result establishes every real condition and needs no further evidence.
Answer and explanation

dissipation: Energy spreading into less readily useful forms or surroundings for the chosen purpose.

Energy spreading into less readily useful forms or surroundings for the chosen purpose. A gives 24 ÷ 120 = 20% as visible light and 96 J in thermal pathways. B gives 30% as visible light and 84 J in thermal pathways. B has a larger modeled light fraction for this purpose, but brightness at the page, price, lifetime, and actual measurements would also matter. Both conserve the stated input energy.

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