Materials Around Us — Tests and Measurements (2 of 3) · Learner pages

Lesson 1 · Test what can be seen through a sample

Classify actual samples as transparent, translucent or opaque using a fair viewing comparison.

Name or initials: ____________   Date: ____________

Seeing a clear shape through a material differs from merely noticing that light reaches the other side. Test the actual sample rather than memorising one label for every form of a material.

1. Check for clear detail. Place a large printed letter behind a clean transparent sample. Keep the letter, lighting, viewing distance and sample position fixed. If the letter is clearly visible, record that observation.
2. Check for a blurred view. Replace only the sample. A translucent sheet allows light through but makes the letter indistinct. The letter can become so blurred that it cannot be recognised even though light passes through.
3. Check whether light passes through. An opaque sample blocks light passing through it, so the letter cannot be seen through it. The supplied sample C transmits no light in this comparison. Absence of letter detail alone is not enough: also check whether light passes through. Do not confuse light or a view around an edge with transmission through the material.
4. Choose a use and state limits. A clear cover suits a display that must be read. A translucent cover can admit light while reducing detail. Thickness, surface treatment and layers can change what is seen; describe the tested sample.

Worked example: A learner keeps one black letter and the same lamp position. Through sheet A the edges are sharp; B transmits light but shows only a pale blurred patch; C blocks light passing through it and no letter is visible through it. The supported classification is A transparent, B translucent and C opaque under those test conditions.

1. A printed word is clearly readable through a sample. The sample is…

   1. Transparent · 2. Translucent · 3. Opaque

2. Light comes through a sheet, but a letter behind it looks blurred. It is…

   1. Opaque in every situation · 2. Always transparent · 3. Translucent

3. To compare two sheets fairly, which should stay the same?

   1. The sheet material and nothing else · 2. The letter, lighting and viewing arrangement · 3. Only the name of the learner

Discuss: Use supplied viewing observations or compare safe clean plastic, tracing paper and card. Keep the printed symbol and lighting unchanged. Do not look at the Sun or a strong light source.

Explain or demonstrate

Classify three supplied or safe actual samples. Record whether light passes through each sample and whether the word can be seen clearly; do not classify from word detail alone.

Evidence to include:

• Same viewing setup
• Light transmission and word detail both recorded
• One stated limitation

Lesson 2 · Compare how materials mix with water

Use observations to distinguish dissolving, suspended material and a separate liquid layer.

Name or initials: ____________   Date: ____________

Small solid grains becoming invisible in water does not mean the material is destroyed. Mixing behaviour depends on the substances and the conditions.

1. Predict and control the comparison. Use supplied records or an adult-supervised test with small labelled amounts of salt, sand and cooking oil, room-temperature water and unbreakable cups. Keep the water amount and stirring time alike. Never taste mixtures or test an unknown substance.
2. Distinguish dissolving from vanishing. A small amount of salt stirred into enough water no longer appears as separate grains. Record that it dissolved. The salt remains in the mixture; invisibility is not evidence of destruction.
3. Record what remains separate. Sand may move through the water when stirred, then settle; it has not dissolved. Oil may break into drops during stirring, then form a separate layer. Waiting after stirring helps distinguish these observations.
4. Generalise carefully. Some liquids mix throughout water while others separate. Some gases, including oxygen, can dissolve in water. Not everything dissolves, and adding ever more solid to a fixed amount of water need not dissolve it all.

Worked example: A supplied record uses 100 mL of water in each cup. A small salt sample leaves no visible grains after stirring; sand leaves a deposit; a little oil forms a layer after resting. These observations support different mixing behaviours. The experiment does not identify every clear liquid as water.

1. Small salt grains disappear from view after stirring into enough water. The best conclusion is…

   1. The salt was destroyed · 2. The water has no other material in it · 3. The salt dissolved and remains in the mixture

2. Sand is stirred into water and later settles. This supports…

   1. The sand changed into water · 2. Sand remained separate rather than dissolved · 3. Every settled material must be soluble

3. Why wait after stirring oil and water?

   1. Separate layers may re-form after temporary droplets · 2. Waiting always makes every liquid dissolve · 3. Waiting removes the oil from existence

Discuss: Write a prediction-observation-conclusion table from the supplied records. Add a control condition and one reason not to infer that an invisible dissolved substance has gone away.

Explain or demonstrate

Use three mixing records to classify outcomes and separate the observations from conclusions.

Evidence to include:

• A prediction for each known material
• Observed grains or layers described
• Conclusion limited to the recorded conditions

Lesson 3 · Measure and compare mass

Read mass values, subtract a container mass and avoid judging mass from size alone.

Name or initials: ____________   Date: ____________

Mass describes how much matter an object contains. Use a suitable balance and report a number with a mass unit. The SI unit of mass is the kilogram (kg).

1. Select a measurement. An appearance-based prediction is a starting idea, not a reading. Use supplied balance data or a suitable classroom balance on a stable surface. Record the unit as well as the number.
2. Account for the holder. The model empty cup reads 20 g. With the sample added, the same cup reads 95 g. The larger reading includes both cup and sample.
3. Calculate the sample mass. Subtract the empty-cup reading: 95 g − 20 g = 75 g. Check by adding back: 75 g + 20 g = 95 g. Use the same holder, or measure each holder separately.
4. Compare mass without assuming size. Equal volumes of two different materials can have different masses. Compare actual readings. In this grade, keep mass in g or kg distinct from volume in mL or L.

Worked example: A tray alone is 40 g. The tray with beads is 165 g, so the beads have mass 125 g. A second set of the same visible volume reads 190 g including the same tray, giving 150 g. The second sample has greater mass; equal visible volume did not force equal mass.

1. A cup is 15 g empty and 85 g with a sample. What is the sample mass?

   1. 85 g · 2. 70 g · 3. 100 g

2. Which unit is the SI unit of mass?

   1. kg · 2. mL · 3. cm

3. Two samples occupy equal volumes. Their masses…

   1. Must always be equal · 2. Must both be zero · 3. Can differ because the materials can differ

Discuss: Make a two-row table with empty-container and filled-container readings. Calculate sample masses, show an addition check and explain why comparing the totals alone can be unfair if the containers differ.

Explain or demonstrate

For supplied pairs of empty and full readings, calculate two sample masses and justify the comparison.

Evidence to include:

• Number and unit on each reading
• Correct subtraction per holder
• Comparison based on sample masses

Final check · Set 1

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

1. A display cover must let people read the notice behind it. Which tested property is needed?

   Softness alone / Dull colour alone / Transparency

2. Why is “every glass sample is transparent” too strong?

   All glass samples have the same surface / Surface treatment such as frosting can blur the view / Glass can never transmit light

3. An undissolved grain sinks. What does sinking alone tell you?

   It cannot have mass / It moved downward; solubility needs separate evidence / It must be soluble

4. Which statement about gases in water is correct?

   Some gases, such as oxygen, can dissolve / No gas can ever dissolve / Every gas dissolves without limit

5. Convert 2 kg to grams.

   2000 g / 200 g / 20 g

6. A 30 g container with a sample reads 120 g. Which check verifies the sample calculation?

   120 g + 30 g = 90 g / 90 g − 30 g = 120 g / 90 g + 30 g = 120 g

Final check · Set 2

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

1. A learner sees a letter around a card’s edge. Does this prove the card is transparent?

   No; the view must pass through the card / Yes; any visible letter proves transparency / Yes; every card is transparent

2. A single sheet is translucent; a thick stack blocks the view. What is a sound record?

   Erase one observation because all layers must match / Conclude no materials admit light / Classify each tested arrangement separately

3. To compare two solids, which change would make interpretation harder?

   Labelling both cups clearly / Recording both observations / Using very different water amounts and stirring times

4. A cup of water has dissolved some sugar. Must any extra amount dissolve?

   No; dissolved sugar is no longer matter / No; a fixed amount of water need not dissolve unlimited sugar / Yes; dissolution has no limit

5. Two filled containers have different empty masses. What is a fair way to compare their contents?

   Assume all containers have mass 0 g / Subtract each container’s own empty mass / Compare only the container colours

6. A big foam block and small metal piece are compared by sight. Which claim is justified without mass readings?

   Their masses still need evidence / The bigger item must have more mass / The smaller item must have no mass