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Science lesson plan · 5th grade (Year 6 in England) · 30 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 · 4 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. 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, 25 g of one chemical reacts with 39 g of another. What is the total mass of the products, in g? → 64 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 250 g to 247.4 g. What mass of gas escaped, in g? → 2.6 gPrompt: Mass is not destroyed. Where did the missing mass go?

Hook · 3 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 · 7 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 · 6 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. 210 g of sand and 20 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 152 g. What is the mass after the fizzing stops? → 152 gPrompt: Can the gas escape?

You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. A sealed bag of 125 g of ice is left until all the ice has melted. What is the mass of the bag of water now (ignore the bag)? → 125 gPrompt: Melting changes the state, not the amount of matter.
  2. 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 288 g. What does the balance show after the fizzing stops? → 286 gPrompt: Can the gas escape?

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/ 6

  1. Question 1

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

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

  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 289 g. What is the mass after the fizzing stops?

    Answerg

  3. Question 3

    A sealed bag of 80 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

  4. Question 4

    Rust forms on an iron nail. The rusty nail has MORE mass than the clean nail. Why?

    • A. Rust is made from nothing.
    • B. Oxygen from the air joined with the iron.
    • C. Rust is always heavier than anything.
    • D. The nail grew longer.

  5. Question 5

    Vinegar and baking soda are mixed inside a sealed plastic bottle on a balance. They fizz and make a gas. The mass before was 180 g. What is the mass after the fizzing stops?

    Answerg

  6. Question 6

    A sealed bag of 235 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

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

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

  2. 2. 289 g

  3. 3. 80 g

  4. 4. B. Oxygen from the air joined with the iron.

  5. 5. 180 g

  6. 6. 235 g