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Science lesson plan · 5th grade (Year 6 in England) · 60 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 · 6 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: toasting bread? (reversible / irreversible) → irreversiblePrompt: Could you get the starting material back?
  2. Which change is reversible? (mixing vinegar and bicarbonate of soda (baking soda) / melting butter / burning wood / toasting bread) → melting butterPrompt: Changes of state and dissolving can be reversed.
  3. Why is burning a candle wick irreversible? (It can be turned back into a wick by cooling / New substances such as carbon dioxide and ash form / Nothing new is made / The wick only melts) → New substances such as carbon dioxide and ash formPrompt: What is left after burning?

Hook · 6 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 · 12 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 · 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. 250 g of chocolate is melted in a bowl. What is the mass of the melted chocolate, in g? → 250 gPrompt: Does a change of state add or remove any material?
  2. In a sealed flask, 87 g of one chemical reacts with 36 g of another. What is the total mass of the products, in g? → 123 gPrompt: In a closed container, atoms are only rearranged.

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. In a sealed flask, 67 g of one chemical reacts with 23 g of another. What is the total mass of the products, in g? → 90 gPrompt: In a closed container, atoms are only rearranged.
  2. Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 256 g to 252.7 g. What mass of gas escaped, in g? → 3.3 gPrompt: Mass is not destroyed. Where did the missing mass go?

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

    An ice cube of 75 g melts completely in a sealed bag. What is the mass of the water, in g?

    Answerg

  2. Question 2

    In a sealed flask, 58 g of one chemical reacts with 49 g of another. What is the total mass of the products, in g?

    Answerg

  3. Question 3

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 190 g to 185.6 g. What mass of gas escaped, in g?

    Answerg

  4. Question 4

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

    Answerg

  5. Question 5

    In a sealed flask, 31 g of one chemical reacts with 32 g of another. What is the total mass of the products, in g?

    Answerg

  6. Question 6

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 236 g to 234.5 g. What mass of gas escaped, in g?

    Answerg

  7. Question 7

    50 g of water is frozen in a sealed tub. What is the mass of the ice, in g?

    Answerg

  8. Question 8

    In a sealed flask, 61 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. 75 g

  2. 2. 107 g

  3. 3. 4.4 g

  4. 4. 340 g

  5. 5. 63 g

  6. 6. 1.5 g

  7. 7. 50 g

  8. 8. 77 g