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Chemistry - Properties of Materials

Grade 7IGCSE

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

🔑Concepts

The Particle Theory of Matter states that all matter is composed of tiny particles. The arrangement and energy of these particles define the state: Solid, Liquid, or Gas.

Physical properties are characteristics that can be observed without changing the substance's identity, such as density, melting pointmelting\ point, boiling pointboiling\ point, and electrical conductivity.

Density is the mass per unit volume of a substance. It is a constant for a pure substance at a given temperature and is expressed as ρ=mV\rho = \frac{m}{V}.

Metals are typically shiny (lustrouslustrous), malleablemalleable (can be hammered into sheets), ductileductile (can be drawn into wires), and are excellent conductors of heat and electricity.

Non-metals are generally brittlebrittle when solid, have lower melting pointsmelting\ points compared to metals, and act as electrical and thermal insulators.

Chemical properties describe how a substance reacts with others. For example, the reaction of Magnesium with Oxygen: 2Mg+O22MgO2Mg + O_2 \rightarrow 2MgO.

Solubility refers to the ability of a solute to dissolve in a solvent. Factors affecting solubility include temperature and the nature of the solutesolute and solventsolvent.

📐Formulae

ρ=mV\rho = \frac{m}{V}

m=ρ×Vm = \rho \times V

ho}$$

Volumerectangular prism=l×w×hVolume_{rectangular\ prism} = l \times w \times h

💡Examples

Problem 1:

A block of unknown metal has a mass of 405g405g and a volume of 150cm3150cm^3. Calculate its density and identify if it could be Aluminum (Density of Aluminum is 2.7g/cm32.7g/cm^3).

Solution:

ρ=405g150cm3=2.7g/cm3\rho = \frac{405g}{150cm^3} = 2.7g/cm^3

Explanation:

By dividing the mass (405g405g) by the volume (150cm3150cm^3), we get a density of 2.7g/cm32.7g/cm^3. Since this matches the known density of Aluminum, the metal is likely Aluminum.

Problem 2:

Describe the change in particle behavior when ice (H2O(s)H_2O(s)) is heated to become liquid water (H2O(l)H_2O(l)).

Solution:

The particles gain kinetic energykinetic\ energy, vibrate more vigorously, and eventually overcome the strong forces of attraction holding them in a fixed latticelattice.

Explanation:

In a solid, particles are in a fixed arrangement. Heating provides energy, allowing particles to slide past one another in the liquid state, though they remain close together.

Problem 3:

An object has a density of 0.8g/cm30.8g/cm^3. If it is placed in a container of water (density 1.0g/cm31.0g/cm^3), will it sink or float?

Solution:

The object will float.

Explanation:

An object floats if its density is less than the density of the fluid it is placed in. Since 0.8g/cm3<1.0g/cm30.8g/cm^3 < 1.0g/cm^3, the object is buoyant.

Properties of Materials - Revision Notes & Key Formulas | IGCSE Grade 7 Science