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.
- Is this change reversible or irreversible: melting butter? (reversible / irreversible) → reversiblePrompt: Could you get the starting material back?
- Which change is reversible? (freezing water into ice / toasting bread / baking a cake / mixing vinegar and bicarbonate of soda (baking soda)) → freezing water into icePrompt: Changes of state and dissolving can be reversed.
- Melted candle wax sets hard again when it cools. This change is… (irreversible / burning / reversible / a chemical reaction) → reversiblePrompt: Is it still wax?
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.
- 50 g of chocolate is melted in a bowl. What is the mass of the melted chocolate, in g? → 50 gPrompt: Does a change of state add or remove any material?
- In a sealed flask, 79 g of one chemical reacts with 45 g of another. What is the total mass of the products, in g? → 124 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.
- Vinegar and bicarbonate of soda (baking soda) react in an open beaker. The mass falls from 222 g to 219.8 g. What mass of gas escaped, in g? → 2.2 gPrompt: Mass is not destroyed. Where did the missing mass go?
- In a sealed flask, 72 g of one chemical reacts with 18 g of another. What is the total mass of the products, in g? → 90 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