Science in Punggol study guide · Article 0012 of 20
Choose a material by matching its properties to the job. A good cooking surface and a good cooking-pot handle may need different properties, even though they belong to the same object.
An explanation should name the required function, the relevant property and how that property helps.
On this page: Begin with what the object must do · Connect a property to its effect · Compare samples fairly · Worked question: absorbing a spill
Begin with what the object must do
For a window, transparency allows light to pass through. For a towel, water absorption helps remove water from a wet surface. For a raincoat’s outer layer, resistance to water passing through helps keep the wearer dry.
These choices answer different requirements. A material that absorbs water well is useful for a towel but may be unsuitable for keeping rain away. No property is best for every purpose.
Some objects must meet several requirements. A reusable bottle may need strength, low mass and resistance to leakage. Evidence about strength alone cannot show that it meets all three.
Connect a property to its effect
Materials can differ in strength, flexibility, transparency, water absorption and their ability to conduct heat or electricity. Select the property that explains the function in the question.
A pot base should transfer thermal energy to the food. Good heat conduction helps it do that. A handle should reduce heat transfer to the user’s hand, so a poor conductor of heat may be more suitable there.
“Metal is strong” might be true for a sample, but it does not answer a question about reducing heat transfer. Use the property that explains the stated task.
Different plastics or metals can have different properties. If test results describe particular samples, use that evidence rather than assuming that every material in the same broad group behaves identically.
Compare samples fairly
To compare water absorption, use samples with the same area and similar thickness. Keep the water supply, contact time and measurement method the same. Differences in the amount of material could otherwise affect the result.
Sometimes the aim is to compare complete products, such as two towels sold in different thicknesses. That can be a useful investigation, but state that it compares the products rather than only their materials.
Decide what will be measured before testing. The volume of water absorbed answers an absorption question. It does not tell us how strong the material is or how long it will last.
Worked question: absorbing a spill
Question: Three samples with matching area and thickness are tested using the same procedure. A absorbs 2 millilitres of water, B absorbs 12 millilitres and C absorbs 5 millilitres. Which is most suitable for absorbing the spill under these conditions?
Worked explanation: Sample B is most suitable for this absorption task because it absorbs the greatest volume of water, 12 millilitres. Greater absorption helps it remove more water from the spill.
Common mistake: “B is the best material for everything.” The results establish only its performance in this absorption comparison. Strength, flexibility and durability would need separate evidence.
This is the useful link: a stated task leads to a relevant property, and a measurement supports the choice. Apply that link when explaining an unfamiliar object.
