Materials Around Us — Volume, Matter and Design (3 of 3) · Answer guide

Lesson 1 · Distinguish volume from capacity

Read a simple volume scale, distinguish contents from container capacity and convert litres to millilitres.

1. A 500 mL capacity bottle contains 200 mL. What is the water volume?

   Answer: 200 mL. Capacity tells what it can hold, while the current contents are 200 mL.

2. A scale has marks at 100, 150 and 200 mL. Each interval represents…

   Answer: 50 mL. Subtract adjacent labels: 150 − 100 = 50 mL.

3. The same water is poured into a wider container without spilling. Its volume…

   Answer: Stays the same although its height can change. Changing the container changes the shape of the same water, not its amount.

Discuss: Sketch two differently shaped containers holding the same stated volume. Explain why their water heights can differ, then write a capacity-and-contents pair with units.

Teaching note: A tall water level does not always mean a larger volume: the container’s width and shape also matter. A 1 L capacity bottle need not currently contain 1 L. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

A 1000 mL container holds 420 mL. Another 180 mL is added without spilling. Calculate the contents and unused capacity, then explain why a new container could show a different water height.

Evidence to include:

• Contents found by addition
• Unused capacity found by subtraction
• Shape distinguished from volume

Review guide:

• 1 point: 600 mL contents
• 1 point: 400 mL capacity remains
• 1 point: wider shape can give a lower water height without changing volume

Example response: 420 + 180 = 600 mL of water. The unused capacity is 1000 − 600 = 400 mL. A wider container could hold this same water at a lower height.

Lesson 2 · Use evidence that air is matter

Explain matter using mass and occupied space, including materials that cannot easily be seen.

1. Which definition matches matter in this lesson?

   Answer: Anything that has mass and occupies space. Both mass and occupied space are needed; matter includes gases.

2. Why can clear air still be matter?

   Answer: It occupies space and has mass even though it is invisible. Visibility is not part of the definition of matter.

3. The same rigid container reads 350.0 g and then 350.4 g after more air is added. The increase is…

   Answer: 0.4 g. Subtract the first reading from the second: 350.4 − 350.0 = 0.4 g.

Discuss: Write an evidence sentence using “mass” and “space” to explain why clear air is matter. Add one sentence describing a limit of the dots-and-container model.

Teaching note: Invisible does not mean absent or massless. More air can occupy the same fixed container volume; do not claim that every increase in mass must increase an object’s outer size. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Interpret the supplied rigid-container data: 620.0 g before and 620.5 g after adding air, with all other contributions unchanged. State the mass change and a model limitation. Do not carry out a pressure experiment.

Evidence to include:

• Mass change calculated
• Air linked to mass and occupied space
• Dots described as a model

Review guide:

• 1 point: 0.5 g increase
• 1 point: air is matter for both stated reasons
• 1 point: no literal dot count or home pressure test

Example response: The increase is 0.5 g. The added air has mass and occupies space inside the container, so it is matter. The dots illustrate air but cannot tell me its real particle count.

Lesson 3 · Choose materials using evidence

Combine several properties to choose a material, test a claim fairly and explain reuse choices.

1. The supplied clear plastic sample is stiff, transparent and resists splashes. Which requirement does transparency address?

   Answer: The display contents must be visible. Transparency supports seeing the contents through the cover.

2. Why compare all three design criteria?

   Answer: A sample can meet one need and fail another. A multi-criterion decision considers several independent needs.

3. In a bounce comparison intended to investigate ball material, what should be held the same?

   Answer: Drop height, surface and release method. Keeping other influences stable helps interpret the effect of the ball being compared.

Discuss: Plan a small useful item from clean intact leftover material. Name two requirements, compare two candidates with evidence, draw the design, and record one change after feedback. Use a drawing or a teacher-approved no-cut assembly.

Teaching note: No single property makes a material best for every task. “Plastic” is a broad material category; its samples can differ in stiffness, transparency and local recycling options. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Create a drawing of a small useful item from a clean intact leftover material. State two requirements, compare two candidates, justify one choice and revise one feature after feedback.

Evidence to include:

• Two measurable or observable requirements
• Candidate comparison with evidence
• One recorded revision

Review guide:

• 1 point: criteria stated
• 1 point: material choice supported by observations
• 1 point: feedback produces an explained revision

Example response: For a label holder I need stiffness and a clear view. The tested transparent sheet meets both needs better than the cloth sample. Feedback shows the label slips, so I fold a lower lip in my drawing and explain how it supports the paper.

Final check · Set 1

Try one set after the lessons. Use the other set after reviewing any errors.

1. Convert 1 L 250 mL to millilitres.

   1250 mL. One litre is 1000 mL; adding 250 gives 1250 mL.

2. An 800 mL jug contains 350 mL. After adding 200 mL without spilling, how much capacity remains?

   250 mL. The contents become 550 mL, leaving 800 − 550 = 250 mL.

3. A drawing uses six dots to represent some air. What is justified?

   The dots are a simplified representation, not literal particle counts. A model symbol has only the meaning stated for it. No literal particle count or dot mass is supplied.

4. More air is added to the same rigid container. Which observation can occur?

   Mass increases while the container’s outside volume stays the same. A rigid container fixes its outside size; more enclosed air can increase mass within that space.

5. Why repeat a classroom comparison when practical?

   To check whether the observations are consistent. Repeated observations help reveal variation or unusual readings. They do not guarantee identical results.

6. The display now needs to hide its contents. What should the team do?

   Revise the criteria and reconsider the material. Changing the purpose changes what counts as a suitable property.

Final check · Set 2

Try one set after the lessons. Use the other set after reviewing any errors.

1. Which is the SI unit of volume?

   m³. The cubic metre is the SI volume unit. A centimetre alone measures length.

2. For a real water measuring cylinder, which reading method is appropriate?

   Cylinder upright and level; read the bottom of the curved water surface at eye level. A stable level cylinder and eye-level view reduce reading errors. The drawing’s flat surface is a simplification.

3. A supplied same-container comparison changes from 480.0 g to 480.3 g. What supports the conclusion that added air has mass?

   Only the air amount changes, and total mass increases by 0.3 g. Holding other contributions unchanged links the mass increase to the added air.

4. Which statement correctly distinguishes transparency from matter?

   A transparent material can still have mass and occupy space. Transparency describes a view through a sample; matter concerns mass and occupied space.

5. A package is labelled plastic. What does this alone establish about local recycling?

   Local acceptance still needs checking. Different plastics, coatings and local collection systems can have different requirements.

6. Which improvement plan produces interpretable feedback?

   Change one design feature, then compare with the same requirements. Documented criteria and a focused change help connect feedback to an improvement.