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Science lesson plan · 5th grade (Year 6 in England) · 45 minutes

Conservation of mass

Materials and their properties

CCSS NGSS.5-PS1-2CCSS NGSS.MS-PS1-5England: KS3 Chemistry: Chemical reactions

Objective and success criteria

Students will: Conservation of mass.

  • 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: Reversible and irreversible changes

Leads to: Mass before and after: sealed and open containers; Conservation of mass in reactions

Materials: A tray of everyday objects, Sorting hoops, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Reversible and irreversible changes). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is this change reversible or irreversible: boiling water into steam? (reversible / irreversible) → reversiblePrompt: Could you get the starting material back?
  2. Which change is reversible? (toasting bread / burning wood / dissolving salt in water / baking a cake) → dissolving salt in waterPrompt: Changes of state and dissolving can be reversed.
  3. How could you get salt back after dissolving it in water? (evaporate the water / burn it / freeze it / filter it) → evaporate the waterPrompt: Leave it somewhere warm and wait.

Hook · 5 min

  • Pass round objects made of different materials and ask why each one was chosen.
  • Share the objective: Conservation of mass. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: An ice cube of 120 g melts completely in a sealed bag. What is the mass of the water, in g?
  • Step 1: Mass is conserved in a change of state.
  • Step 2: So the answer is: 120 g
  • Answer: 120 g
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 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. 340 g of chocolate is melted in a bowl. What is the mass of the melted chocolate, in g? → 340 gPrompt: Does a change of state add or remove any material?
  2. In a sealed flask, 21 g of one chemical reacts with 55 g of another. What is the total mass of the products, in g? → 76 gPrompt: In a closed container, atoms are only rearranged.

You do: independent practice · 10 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 · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. An ice cube of 50 g melts completely in a sealed bag. What is the mass of the water, in g? → 50 gPrompt: Does a change of state add or remove any material?
  2. In a sealed flask, 85 g of one chemical reacts with 57 g of another. What is the total mass of the products, in g? → 142 gPrompt: In a closed container, atoms are only rearranged.

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: Reversible and irreversible changes.
  • Use concrete materials: a tray of everyday objects.
  • 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: Mass before and after: sealed and open containers; Conservation of mass in reactions.
  • 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-5.

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

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Conservation of mass

Name

Date

Score/ 8

  1. Question 1

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 210 g to 205.6 g. What mass of gas escaped, in g?

    Answerg

  2. Question 2

    In a sealed flask, 74 g of one chemical reacts with 33 g of another. What is the total mass of the products, in g?

    Answerg

  3. Question 3

    200 g of chocolate is melted in a bowl. What is the mass of the melted chocolate, in g?

    Answerg

  4. Question 4

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 163 g to 160.4 g. What mass of gas escaped, in g?

    Answerg

  5. Question 5

    In a sealed flask, 75 g of one chemical reacts with 43 g of another. What is the total mass of the products, in g?

    Answerg

  6. Question 6

    250 g of chocolate is melted in a bowl. What is the mass of the melted chocolate, in g?

    Answerg

  7. Question 7

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 203 g to 198.6 g. What mass of gas escaped, in g?

    Answerg

  8. Question 8

    In a sealed flask, 68 g of one chemical reacts with 16 g of another. What is the total mass of the products, in g?

    Answerg

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Answer key: Conservation of mass

  1. 1. 4.4 g

  2. 2. 107 g

  3. 3. 200 g

  4. 4. 2.6 g

  5. 5. 118 g

  6. 6. 250 g

  7. 7. 4.4 g

  8. 8. 84 g