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Science lesson plan · 5th grade (Year 6 in England) · 60 minutes

Mass before and after: sealed and open containers

Materials and their properties

CCSS NGSS.5-PS1-2England: KS2 Y5 Properties and changes of materialsEngland: KS3 Chemistry: Chemical reactions

Objective and success criteria

Students will: Mass before and after: sealed and open containers.

  • 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: Conservation of mass

Leads to: the next skill in this area.

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 (Conservation of mass). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. 120 g of water is frozen in a sealed tub. What is the mass of the ice, in g? → 120 gPrompt: Does a change of state add or remove any material?
  2. In a sealed flask, 85 g of one chemical reacts with 30 g of another. What is the total mass of the products, in g? → 115 gPrompt: In a closed container, atoms are only rearranged.
  3. Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 206 g to 204.9 g. What mass of gas escaped, in g? → 1.1 gPrompt: Mass is not destroyed. Where did the missing mass go?

Hook · 6 min

  • Pass round objects made of different materials and ask why each one was chosen.
  • Share the objective: Mass before and after: sealed and open containers. 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: 165 g of water and 15 g of salt are stirred until the salt dissolves. What is the total mass?
  • Step 1: 165 + 15 = 180
  • Step 2: So the answer is: 180 g
  • Answer: 180 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. 220 g of sand and 10 g of iron filings are mixed together. What is the total mass? → 230 gPrompt: Nothing is added or taken away.
  2. Vinegar and baking soda are mixed inside a sealed plastic bottle on a balance. They fizz and make a gas. The mass before was 174 g. What is the mass after the fizzing stops? → 174 gPrompt: Can the gas escape?

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. Vinegar and baking soda are mixed in an OPEN cup on a balance. They fizz and 2 g of gas escapes into the air. The mass before was 184 g. What does the balance show after the fizzing stops? → 182 gPrompt: Can the gas escape?
  2. 80 g of water and 50 g of salt are stirred until the salt dissolves. What is the total mass? → 130 gPrompt: Nothing is added or taken away.

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: Conservation of mass.
  • 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

  • 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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Mass before and after: sealed and open containers

Name

Date

Score/ 8

  1. Question 1

    75 g of water and 30 g of salt are stirred until the salt dissolves. What is the total mass?

    Answerg

  2. Question 2

    Vinegar and baking soda are mixed inside a sealed plastic bottle on a balance. They fizz and make a gas. The mass before was 222 g. What is the mass after the fizzing stops?

    Answerg

  3. Question 3

    A sealed flask of water is weighed, heated until some water boils into steam, then weighed again with the lid still on. What happens to the mass?

    • A. It stays the same.
    • B. It becomes zero.
    • C. It goes down.
    • D. It goes up.

  4. Question 4

    165 g of water and 15 g of salt are stirred until the salt dissolves. What is the total mass?

    Answerg

  5. Question 5

    Vinegar and baking soda are mixed in an OPEN cup on a balance. They fizz and 5 g of gas escapes into the air. The mass before was 166 g. What does the balance show after the fizzing stops?

    Answerg

  6. Question 6

    Why do scientists use a sealed container to show that mass is conserved in a reaction that makes a gas?

    • A. So the gas turns into a liquid.
    • B. So the gas cannot escape and every particle is still weighed.
    • C. Because open containers break.
    • D. So the reaction goes faster.

  7. Question 7

    A sealed bag of 300 g of ice is left until all the ice has melted. What is the mass of the bag of water now (ignore the bag)?

    Answerg

  8. Question 8

    Vinegar and baking soda are mixed in an OPEN cup on a balance. They fizz and 2 g of gas escapes into the air. The mass before was 217 g. What does the balance show after the fizzing stops?

    Answerg

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Answer key: Mass before and after: sealed and open containers

  1. 1. 105 g

  2. 2. 222 g

  3. 3. A. It stays the same.

  4. 4. 180 g

  5. 5. 161 g

  6. 6. B. So the gas cannot escape and every particle is still weighed.

  7. 7. 300 g

  8. 8. 215 g