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      Lesson details

      Learning outcome

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

      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.

      Teacher tip

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

      Licence

      This content is © Oak National Academy Limited (2026), 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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      Prior knowledge starter quiz

      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

      To help you plan your 8 science lesson on: Heating and cooling, download all teaching resources for free and adapt to suit your pupils' needs...