step 1 of 6
You have used property words to choose materials. Now follow the class's clip choice from the lesson. The clip must resist a coin scratch, lift with a magnet and not dissolve in water.
Which tests check all three needs?
Advanced Material Properties
Compare and group everyday materials based on advanced properties: hardness, solubility, transparency, electrical and thermal conductivity, and response to magnets
What a learner can do afterwards
- Define and test for at least four properties: hardness, solubility, conductivity, magnetism
- Group a set of materials based on test results for each property
- Use results to explain why certain materials are chosen for specific uses (e.g. copper for wires because it conducts electricity)
1 · Read
You know words for material properties. Now compare test results. In a scratch test, hardness means resistance to scratching. Ask an adult to choose safe scrap samples. Use the same tool and pressure on each. A true scratch is a groove, not a streak rubbed off the tool. A sample that stays unscratched resists this test better than one that scratches.
Check light by looking through a sample toward a picture. Transparent materials give a clear view. Translucent materials pass light but blur the view. Opaque materials block visible light. Clear glass is transparent; a wooden board is opaque. A magnet test cannot show whether a view will be clear.
Electrical conductivity describes how readily current flows. Thermal conductivity describes heat transfer. Copper and aluminum conduct both well. Steel also conducts heat and electricity. Iron and many steels are strongly attracted to a classroom magnet. Copper, aluminum, wood and ordinary plastic are not strongly attracted. Bring the same magnet equally close to each sample to compare attraction. A magnet result does not measure conductivity.
Solubility means ability to dissolve in a liquid. A small amount of sugar dissolves in water; sand does not. Dissolved sugar remains in the water even when its grains are invisible. Melting instead changes a solid into a liquid. Breaking into pieces or softening alone is not proof of dissolving. Compare small equal samples using the same amount and temperature of water and the same stirring time.
For an electrical test, an adult sets up a low-voltage battery, bulb and wires with a gap for the sample. Check that copper in the gap lights the bulb. Swap in each sample without changing the rest. A lit bulb shows enough current passes to light it. If copper does not light the bulb, fix the setup and repeat the sample tests. Never use sockets or appliances.
Try it together
A class needs a clip that resists a coin scratch, can be lifted by a magnet and does not dissolve in water. Under the same pressure, the coin scratches P but not Q or R. The magnet lifts R off the table but does not pull P or Q. R stays unchanged in the water test too. Choose R because its results match all three needs. These results do not show its electrical conductivity.
Choose the property before grouping samples. Two samples may belong together by their water results but differ in scratch resistance. For a group needing two properties, keep only samples that meet both conditions, then count them if asked. Record each test separately. A water test cannot establish magnetic attraction, and a magnet test cannot establish electrical conductivity.
To compare heat transfer, an adult can place equal-sized samples in warm, not hot, water. Compare temperature changes at their other ends after the same time. Keep the water temperature and length in the water the same. Do not use flames, boiling water or appliances. A material that transfers heat readily can suit a pan, whose job is to pass heat toward food.
Test properties separately under matching conditions. Group samples by the requested results, then match those results to the job.
The readings and flashcards were written for this dataset. Physical properties is a linked Khan Academy video.
More to read
Sort the records by one rule
A set of samples can make several different groups. Choose a rule before sorting.
For a group based on scratching, use the scratch records. Two samples can belong together by that rule even if a magnet pulls only one of them. Keep those magnet results for a different grouping.
Some jobs need two properties at once. Check each requirement and keep only samples that meet both. A sample meeting just one requirement does not belong in that two-property group.
Describe what happened in water
Pieces becoming smaller is not enough to show that a solid dissolved. A material may crumble or soften while solid remains.
Compare small samples with the same amount and temperature of water and the same stirring time. Record what remains. If a sample stays unchanged, say that it did not dissolve during that test.
Sugar that dissolves remains in the water. Melting is different: the material itself changes from solid to liquid. Water-solubility results do not establish magnetic attraction or scratch resistance.
Check the equipment first
An adult can prepare a low-voltage battery circuit with a bulb and a gap for a sample. Before testing samples, put copper in the gap. The bulb should light.
Replace copper with each sample without changing the other parts. A lit bulb shows enough current passes to light it. A dark bulb does not prove that absolutely no current passes.
If the copper check fails, repair the setup and repeat the affected sample tests. Never use sockets, powered appliances or damaged batteries.
Test the actual sample
Iron and many steels are strongly attracted to a classroom magnet. Nickel and cobalt also show strong magnetic responses. Copper and aluminum do not show that strong attraction.
Different steels can respond differently. Test the actual sample instead of deciding from the word metal or from its color. Use the same magnet and bring it equally close each time.
Record attraction separately from electrical and thermal conductivity. A sample's magnet result does not tell you how readily it carries current or transfers heat.
Look for a true scratch
In this lesson, a hardness comparison concerns resistance to scratching. An adult should choose safe scrap samples that may be marked without damage to useful objects.
Use the same tool and pressure on each sample. Look for a groove. A streak rubbed off the tool may look like a scratch without being one.
Report the comparison you made: one sample resisted that tool better than another. Do not use this result to claim that the sample is less flexible, insoluble or electrically insulating.
Explore more
2 · Watch
3 · Play
Take it off screen
Print a worksheetA4 with an answer key page for grown-ups. No screen, no internet.
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
Then practise
24 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.