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Science lesson plan · 7th grade (Year 8 in England) · 30 minutes

Melting and boiling points

States of matter

CCSS NGSS.MS-PS1-4England: KS3 Chemistry: The particulate nature of matterEngland: KS4 Combined Science: Particle model of matter

Objective and success criteria

Students will: Melting and boiling points.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Temperatures of water changing state; The particle model

Leads to: Specific heat capacity and latent heat

Materials: Ice, water and a kettle (teacher demo), Particle diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Temperatures of water changing state; The particle model). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which state is described: particles with lots of empty space between them? (solid / liquid / gas) → gasPrompt: How close are the particles, and how do they move?
  2. Water in a pan starts at 19 °C. By how many degrees must it warm up to reach its boiling point? → 81 °CPrompt: At what temperature does water boil?
  3. Which state is described: particles packed in a regular pattern? (solid / liquid / gas) → solidPrompt: How close are the particles, and how do they move?

Hook · 3 min

  • Show an ice cube melting and a kettle steaming and ask what is the same and what is different.
  • Share the objective: Melting and boiling points. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Nitrogen melts at −210 °C and boils at −196 °C. What state is it in at −218 °C?
  • Step 1: −218 < −210
  • Step 2: So the answer is: solid
  • Answer: solid
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Copper melts at 1085 °C and boils at 2562 °C. What state is it in at 1824 °C? (solid / liquid / gas) → liquidPrompt: Is the temperature below the melting point, between the two, or above the boiling point?
  2. Iron melts at 1538 °C and boils at 2862 °C. Over how many degrees is it a liquid? → 1324 °CPrompt: It is a liquid between its melting point and its boiling point.

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Ethanol melts at −114 °C and boils at 78 °C. What state is it in at 113 °C? (solid / liquid / gas) → gasPrompt: Is the temperature below the melting point, between the two, or above the boiling point?
  2. Ethanol melts at −114 °C and boils at 78 °C. Over how many degrees is it a liquid? → 192 °CPrompt: It is a liquid between its melting point and its boiling point.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Temperatures of water changing state.
  • Use concrete materials: ice, water and a kettle (teacher demo).
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Specific heat capacity and latent heat.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-7.

Free lesson plan from eurekami.com/lesson-plan-builder

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Melting and boiling points

Name

Date

Score/ 6

  1. Question 1

    Which of these substances is a liquid at room temperature (20 °C)? oxygen: melts −218 °C, boils −183 °C sulfur: melts 115 °C, boils 445 °C iron: melts 1538 °C, boils 2862 °C bromine: melts −7 °C, boils 59 °C

    • A. oxygen
    • B. bromine
    • C. sulfur
    • D. iron

  2. Question 2

    Iron melts at 1538 °C and boils at 2862 °C. What state is it in at 2911 °C?

    • A. solid
    • B. liquid
    • C. gas

  3. Question 3

    Oxygen melts at −218 °C and boils at −183 °C. Over how many degrees is it a liquid?

    Answer°C

  4. Question 4

    Which of these substances is a liquid at room temperature (20 °C)? iron: melts 1538 °C, boils 2862 °C bromine: melts −7 °C, boils 59 °C copper: melts 1085 °C, boils 2562 °C sulfur: melts 115 °C, boils 445 °C

    • A. bromine
    • B. iron
    • C. sulfur
    • D. copper

  5. Question 5

    Sulfur melts at 115 °C and boils at 445 °C. What state is it in at 280 °C?

    • A. solid
    • B. liquid
    • C. gas

  6. Question 6

    Bromine melts at −7 °C and boils at 59 °C. Over how many degrees is it a liquid?

    Answer°C

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Answer key: Melting and boiling points

  1. 1. B. bromine

  2. 2. C. gas

  3. 3. 35 °C

  4. 4. A. bromine

  5. 5. B. liquid

  6. 6. 66 °C