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Chemistry - Testing and comparing materials for specific uses

Grade 4Cambridge (IGCSE)

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Materials are chosen for specific uses based on their physical properties such as hardness, flexibility, transparency, and pHpH levels.

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A 'Fair Test' is a scientific investigation where only one variable (the independent variable) is changed, while all others are kept constant to ensure valid results.

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Thermal conductivity measures how well heat, represented as QQ, moves through a material. Metals like Copper (CuCu) are good conductors, while wood and plastic are insulators.

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Electrical conductivity is the ability of a material to allow an electric current to flow. Materials like Aluminum (AlAl) are used in wiring due to high conductivity.

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Solubility is the property of a solid (solute), such as Salt (NaClNaCl), to dissolve in a liquid (solvent), such as Water (H2OH_2O).

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Absorbency is the ability of a material to soak up liquid. For example, a sponge is more absorbent than a plastic sheet because it can hold more volume VV of water.

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Magnetism is a property where certain materials, like Iron (FeFe), are attracted to magnets.

📐Formulae

Density=MassVolume\text{Density} = \frac{\text{Mass}}{\text{Volume}}

Total Mass=Mass of Solute+Mass of Solvent\text{Total Mass} = \text{Mass of Solute} + \text{Mass of Solvent}

ΔT=Tfinal−Tinitial\Delta T = T_{final} - T_{initial}

💡Examples

Problem 1:

An engineer needs to select a material for a bridge. They test three materials by applying a force FF until the material breaks. Material A breaks at 100 N100\,N, Material B at 500 N500\,N, and Material C at 250 N250\,N. Which material is the strongest?

Solution:

Material B is the strongest.

Explanation:

Strength is the ability to withstand an applied force FF without breaking. Since Material B supported the highest force (500 N500\,N), it is the most suitable for a bridge.

Problem 2:

A student tests the solubility of Sugar (C12H22O11C_{12}H_{22}O_{11}) in water at different temperatures. At 20∘C20^\circ C, 200 g200\,g dissolves. At 50∘C50^\circ C, 260 g260\,g dissolves. What is the change in mass Δm\Delta m dissolved?

Solution:

Δm=60 g\Delta m = 60\,g

Explanation:

Using the subtraction of mass, 260 g−200 g=60 g260\,g - 200\,g = 60\,g. This shows that increasing the temperature increases the solubility of the solute.

Problem 3:

Which material would be best for a frying pan handle to prevent heat from reaching the hand: Copper (CuCu), Iron (FeFe), or Wood?

Solution:

Wood

Explanation:

Metals like CuCu and FeFe have high thermal conductivity, meaning heat QQ travels through them quickly. Wood is a thermal insulator and will keep the handle cool.