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Science lesson plan · 5th grade (Year 6 in England) · 30 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 · 4 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: burning wood? (reversible / irreversible) → irreversiblePrompt: Could you get the starting material back?
  2. Which change is irreversible? (dissolving salt in water / an iron nail rusting / melting butter / boiling water into steam) → an iron nail rustingPrompt: Changes of state and dissolving can be reversed.
  3. Which is a sign that a new material has been made? (ice changes to water / a puddle dries up / bubbles of gas are given off when two substances mix / sugar disappears in tea) → bubbles of gas are given off when two substances mixPrompt: The other three are changes of state or dissolving.

Hook · 3 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 · 7 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 · 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. 340 g of water is frozen in a sealed tub. What is the mass of the ice, in g? → 340 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.

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. Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 248 g to 244.7 g. What mass of gas escaped, in g? → 3.3 gPrompt: Mass is not destroyed. Where did the missing mass go?
  2. In a sealed flask, 55 g of one chemical reacts with 60 g of another. What is the total mass of the products, in g? → 115 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/ 6

  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

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 220 g to 215.6 g. What mass of gas escaped, in g?

    Answerg

  3. Question 3

    In a sealed flask, 86 g of one chemical reacts with 58 g of another. What is the total mass of the products, in g?

    Answerg

  4. Question 4

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

    Answerg

  5. Question 5

    Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 247 g to 242.6 g. What mass of gas escaped, in g?

    Answerg

  6. Question 6

    In a sealed flask, 87 g of one chemical reacts with 59 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. 4.4 g

  3. 3. 144 g

  4. 4. 200 g

  5. 5. 4.4 g

  6. 6. 146 g