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Science lesson plan · 8th grade (Year 9 in England) · 60 minutes

Group 1: the alkali metals and their trend

Atoms, elements and the periodic table

CCSS NGSS.MS-PS1-1CCSS NGSS.HS-PS1-1England: KS3 Chemistry: The periodic tableEngland: GCSE Combined Science: Atomic structure and the periodic table

Objective and success criteria

Students will: Group 1: the alkali metals and their trend.

  • 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: The periodic table: groups and periods

Leads to: the next skill in this area.

Materials: Periodic tables, Atom model kits, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 6 min

  • Quick retrieval from earlier learning (The periodic table: groups and periods). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which family does fluorine belong to? (alkali metals (group 1) / halogens (group 17, also called group 7) / noble gases (group 18, also called group 0)) → halogens (group 17, also called group 7)Prompt: Is it a soft metal, a coloured reactive non-metal, or an unreactive gas?
  2. Which family does lithium belong to? (alkali metals (group 1) / halogens (group 17, also called group 7) / noble gases (group 18, also called group 0)) → alkali metals (group 1)Prompt: Is it a soft metal, a coloured reactive non-metal, or an unreactive gas?
  3. Which family does potassium belong to? (alkali metals (group 1) / halogens (group 17, also called group 7) / noble gases (group 18, also called group 0)) → alkali metals (group 1)Prompt: Is it a soft metal, a coloured reactive non-metal, or an unreactive gas?

Hook · 6 min

  • Show the periodic table and ask what patterns students can see before anything is explained.
  • Share the objective: Group 1: the alkali metals and their trend. Read the success criteria together.

I do: model it · 12 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Complete the word equation: lithium + water → ? + hydrogen
  • Step 1: alkali metal + water → metal hydroxide + hydrogen
  • Step 2: So the answer is: lithium hydroxide
  • Answer: lithium hydroxide
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 12 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. Complete the word equation: lithium + water → ? + hydrogen → lithium hydroxidePrompt: The solution left is alkaline.
  2. Why does reactivity increase down group 1? (The atoms have more outer electrons / The atoms get smaller / The nucleus loses protons / The outer electron is further from the nucleus, so it is lost more easily) → The outer electron is further from the nucleus, so it is lost more easilyPrompt: All group 1 atoms have one outer electron.

You do: independent practice · 17 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. The alkali metals: which statement is NOT true? (Sodium is less dense than water, so it floats. / Alkali metals are found pure in nature. / Group 1 metals are soft enough to cut with a knife. / Alkali metals react with water to make alkaline solutions.) → Alkali metals are found pure in nature.Prompt: Which way does reactivity change down the group?
  2. Melting points: lithium 181 °C, sodium 98 °C, potassium 63 °C, rubidium 39 °C. Which is the best prediction for caesium? (about 200 °C / about 300 °C / about 75 °C / about 29 °C) → about 29 °CPrompt: Follow the trend down the group.

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: The periodic table: groups and periods.
  • Use concrete materials: periodic tables.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • 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-8.

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

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Group 1: the alkali metals and their trend

Name

Date

Score/ 8

  1. Question 1

    Complete the word equation: lithium + water → lithium hydroxide + ?

    Answer

  2. Question 2

    The alkali metals: which statement is NOT true?

    • A. Group 1 metals are soft enough to cut with a knife.
    • B. Lithium is the most reactive alkali metal.
    • C. Alkali metals form ions with a 1+ charge.
    • D. Sodium is less dense than water, so it floats.

  3. Question 3

    Melting points: lithium 181 °C, sodium 98 °C, potassium 63 °C, rubidium 39 °C. Which is the best prediction for caesium?

    • A. about 29 °C
    • B. about 200 °C
    • C. about 300 °C
    • D. about 75 °C

  4. Question 4

    Complete the word equation: potassium + water → potassium hydroxide + ?

    Answer

  5. Question 5

    Lithium fizzes gently in water, sodium melts into a ball and whizzes around, and potassium bursts into a lilac flame. What does this show?

    • A. Reactivity increases down group 1
    • B. Reactivity decreases down group 1
    • C. Potassium is not in group 1
    • D. All group 1 metals react the same

  6. Question 6

    Complete the word equation: potassium + water → ? + hydrogen

    Answer

  7. Question 7

    Why does reactivity increase down group 1?

    • A. The outer electron is further from the nucleus, so it is lost more easily
    • B. The atoms get smaller
    • C. The atoms have more outer electrons
    • D. The nucleus loses protons

  8. Question 8

    Complete the word equation: lithium + water → ? + hydrogen

    Answer

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Answer key: Group 1: the alkali metals and their trend

  1. 1. hydrogen

  2. 2. B. Lithium is the most reactive alkali metal.

  3. 3. A. about 29 °C

  4. 4. hydrogen

  5. 5. A. Reactivity increases down group 1

  6. 6. potassium hydroxide

  7. 7. A. The outer electron is further from the nucleus, so it is lost more easily

  8. 8. lithium hydroxide