The properties of materials

Sensory properties are perceived through the senses. Describe the colour, lustre and texture of three objects in your classroom (the desk, a ruler, the whiteboard) and explain which sense you use to identify each of those properties.

Classify these properties into mechanical, thermal, electrical or sensory: hardness, thermal conductivity, lustre, elasticity, electrical conductivity, colour. Then give an example of an object in which each one is the key property.

The figure shows a hardness scale with several materials ordered from softest to hardest, but one of them has lost its name, as shown in the diagram.

Which material that you know could fill the gap? Reason your answer by comparing it with its neighbours on the scale, and then place two other materials on the scale: your fingernail and diamond.

A copper coin scratches plaster, but does not scratch steel; a fingernail scratches plaster, but does not scratch the coin. Order these four materials from least to most hard and explain what simple test you have used to order them (the "scratch test").

Glass is very hard (it hardly scratches at all), but it breaks if dropped on the floor. Explain the difference between hardness and brittleness using this example, and name another hard and brittle material, as well as one that is soft but hard to break.

Classify these materials into electrical conductors and insulators: copper, plastic, dry wood, steel, rubber. Explain why this property determines which material goes inside and which goes outside a cable.

Cooking pots are made of metal, but the handle is usually made of wood or plastic. Explain this using thermal conductivity and reason what would happen with a pot made of a single piece of steel, handle included.

An electrical cable is copper on the inside and plastic on the outside. Explain what property each layer provides and reason what could happen if the cable gets stripped and the copper is exposed.

Match each property with its definition: (a) hardness, (b) elasticity, (c) electrical conductivity, (d) density. Definitions: 1. ability to regain shape after being deformed; 2. resistance to being scratched or worn away; 3. ease of allowing electrical current to pass through; 4. ratio between the mass of a material and the volume it occupies.

True or false? Justify each answer: (a) copper is a good electrical conductor; (b) rubber is a very hard material; (c) a piece of steel weighs more than a piece of cork of the same size because it is denser; (d) glass is an elastic material.

A cork cube and a steel cube of the same size do not weigh the same. Explain which property accounts for this, reason why cork floats in water and steel sinks, and what the density of water has to do with it.

The school wants to buy new chairs for the classroom. Prioritise the three most important properties (strength, light weight so they can be moved easily, ease of cleaning, comfort, etc.), choose one material for the frame and another for the seat, and explain which materials you rule out and why.

A copper saucepan with a wooden handle costs considerably more than one made entirely of steel. Analyse which properties explain this design (copper spreads heat very evenly, wood hardly heats up) and reason whether the extra cost is worth it for cooking on a low heat.

You are going to choose the material for a reusable bottle: stainless steel, hard plastic or glass. Create a decision matrix with four criteria (weight, drop resistance, hygiene and taste, price), score each material from 1 to 3, and draw a reasoned conclusion from your table.

You can do it on paper and send a photo with your answer.