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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 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?
  2. Which family does helium belong to? (alkali metals (group 1) / halogens (group 17, also called group 7) / noble gases (group 18, also called group 0)) → noble gases (group 18, also called group 0)Prompt: Is it a soft metal, a coloured reactive non-metal, or an unreactive gas?
  3. Which family does chlorine 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?

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: sodium + water → sodium hydroxide + ? → hydrogenPrompt: The gas formed burns with a squeaky pop.
  2. Why are alkali metals stored under oil? (to stop them reacting with oxygen and water vapour in the air / because they are liquids / to make them shiny / to keep them warm) → to stop them reacting with oxygen and water vapour in the airPrompt: What happens to a freshly cut piece of sodium in air?

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? (Lithium is the most reactive alkali metal. / Alkali metals form ions with a 1+ charge. / Alkali metals react with water to make alkaline solutions. / Sodium is less dense than water, so it floats.) → Lithium is the most reactive alkali metal.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 29 °C / about 200 °C / about 75 °C / about 300 °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: potassium + water → potassium hydroxide + ?

    Answer

  2. Question 2

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

  3. Question 3

    The alkali metals: which statement is NOT true?

    • A. Lithium is the most reactive alkali metal.
    • B. Alkali metals form ions with a 1+ charge.
    • C. Sodium is less dense than water, so it floats.
    • D. Alkali metals react with water to make alkaline solutions.

  4. Question 4

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

    Answer

  5. Question 5

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

    Answer

  6. Question 6

    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

  7. Question 7

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

    Answer

  8. Question 8

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

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

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

  1. 1. hydrogen

  2. 2. C. Reactivity increases down group 1

  3. 3. A. Lithium is the most reactive alkali metal.

  4. 4. hydrogen

  5. 5. potassium hydroxide

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

  7. 7. hydrogen

  8. 8. C. about 29 °C