New
New
Year 8

Heating and cooling

I can explain why some changes of state are exothermic and some are endothermic.

New
New
Year 8

Heating and cooling

I can explain why some changes of state are exothermic and some are endothermic.

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Lesson details

Key learning points

  1. Heating transfers energy into a substance and can cause it to melt, evaporate or boil.
  2. Melting, evaporation and boiling are endothermic.
  3. As it cools, a substance transfers energy into the surroundings by heating and it may condense or freeze.
  4. Condensing and freezing are exothermic.

Keywords

  • Endothermic - When a substance transfers energy in from the surroundings, e.g. melting, boiling and evaporating.

  • Exothermic - When a substance transfers energy out to the surroundings by heating, e.g. condensing and freezing.

Common misconception

Energy can appear and disappear.

Remind students about the conservation of energy.

Show a demonstration of stearic acid cooling taking temperature at regular time intervals.
Teacher tip

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
What is the state of water at room temperature (about 20°C)?
Solid
Correct answer: Liquid
Gas
Q2.
Which of these is not a characteristic of a solid state substance?
Fixed shape
Cannot be compressed
Correct answer: Flows easily
Particles in fixed positions
Q3.
Water will melt at ℃?
Correct Answer: 0, zero
Q4.
In what state does water evaporate ?
Solid
Correct answer: Liquid
Gas
Q5.
What happens to the volume of a substance when it condenses?
Increases
Correct answer: Decreases
Stays the same
Becomes zero
Q6.
How does the energy of particles compare between a block of ice at -10°C and a glass of water at 20°C?
Correct answer: Higher in the glass of water
Higher in the block of ice
The same in both
Impossible to determine

6 Questions

Q1.
What type of process is boiling?
Correct answer: Endothermic
Exothermic
Both
Neither
Q2.
When energy is transferred out from a substance to its surroundings, this process is termed...
Correct Answer: exothermic, exo-thermic, exo thermic
Q3.
Which thermometer shows the temperature at which water is in the liquid state?
An image in a quiz
a
b
Correct answer: c
Q4.
Evaporation is an endothermic process because energy is transferred from the surroundings into the substance.
Correct answer: true
false
Q5.
Match the statements below to what is happening in terms of energy, particle movement and particle arrangement as a substance is heated over time.
An image in a quiz
Correct Answer:Between A and B,particles are in fixed positions, and vibrate more

particles are in fixed positions, and vibrate more

Correct Answer:Between B and C,particles becoming randomly arranged and can move

particles becoming randomly arranged and can move

Correct Answer:Between C and D,particles in liquid state move past each other and faster

particles in liquid state move past each other and faster

Correct Answer:Between D and E,energy used to overcome liquid particle attractive forces

energy used to overcome liquid particle attractive forces

Correct Answer:Between E and F,particles in gas state use energy to move faster

particles in gas state use energy to move faster

Q6.
Starting in the liquid state, if a substance's particles increase in energy while its temperature remains constant, what change is happening? Give a one-word answer.
Correct Answer: boiling
Q5 UYSEG