Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Materials have physical properties that make them suitable for specific tasks. These include hardness, flexibility, transparency, and conductivity.
Hardness is a measure of how easily a material can be scratched or dented. Diamond is one of the hardest known natural materials.
Flexibility is the ability of a material to bend without breaking. Materials like rubber are highly flexible, whereas glass is brittle.
Waterproof materials do not allow to pass through them or soak into them. Materials that soak up are called absorbent.
Transparency describes how much light passes through a material: transparent (all light), translucent (some light), or opaque (no light).
Thermal Conductivity refers to how well heat moves through a material. Metals are good conductors, while wood and plastic are thermal insulators.
Electrical Conductivity is the ability of a material to allow electricity to flow. Metals like copper are used in wiring because they conduct electricity well.
📐Formulae
💡Examples
Problem 1:
Why is an umbrella canopy made of nylon or plastic rather than cotton or paper?
Solution:
Nylon and plastic are waterproof and flexible.
Explanation:
An umbrella must be waterproof to prevent from passing through to the person underneath. It must also be flexible so it can be folded and unfolded without snapping.
Problem 2:
Why are electrical wires usually made of copper but covered in a layer of plastic?
Solution:
Copper is a conductor, while plastic is an insulator.
Explanation:
Copper allows the flow of electricity, while the plastic coating acts as an insulator to prevent the electricity from traveling to or human skin, which could cause a shock.
Problem 3:
Which material property makes glass suitable for windows, and which property makes it a poor choice for a football?
Solution:
Suitability: Transparency; Poor choice: Brittleness (Low flexibility/strength).
Explanation:
Glass is transparent, allowing light to enter a room. However, it is brittle and breaks easily under impact, making it unsuitable for a high-impact object like a ball.