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Particulate Nature of Matter - How Particles Move in Different States of Matter

Grade 8CBSE

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

🔑Concepts

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Matter is composed of tiny particles that are in a state of continuous motion. This is known as the Kinetic Theory of Matter.

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Particles possess Kinetic Energy (K.E.K.E.) due to their motion. The magnitude of this energy determines the state of matter.

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In the Solid State, particles are tightly packed with very strong intermolecular forces. They do not move from their positions but only vibrate about their mean positions.

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In the Liquid State, particles have more space between them compared to solids. They move randomly within the bulk of the liquid and can slide over each other, allowing liquids to flow.

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In the Gaseous State, particles have maximum intermolecular space and negligible intermolecular forces. They move randomly at very high speeds (vv) in all directions.

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Diffusion is the process of intermixing of particles of two different types of matter on their own. The rate of diffusion is fastest in gases and slowest in solids.

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The Kinetic Energy of particles is directly proportional to the absolute temperature (TT). As temperature increases, particles move faster: K.E.∝TK.E. \propto T.

📐Formulae

K.E.=12mv2K.E. = \frac{1}{2}mv^2

Density(ρ)=Mass(m)Volume(V)\text{Density} (\rho) = \frac{\text{Mass} (m)}{\text{Volume} (V)}

T(K)=T(∘C)+273.15T(K) = T(^{\circ}C) + 273.15

💡Examples

Problem 1:

Why does the smell of hot sizzling food reach you several meters away, but to get the smell from cold food you have to go close?

Solution:

At higher temperatures, the particles of the aroma of food possess higher Kinetic Energy (K.E.K.E.). This increases the rate of diffusion into the air. Since K.E.∝TK.E. \propto T, the particles move much faster at higher temperatures, covering larger distances quickly.

Explanation:

This demonstrates the relationship between temperature and the velocity of particles in the gaseous state.

Problem 2:

A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Solution:

This observation shows that particles of matter have spaces between them and that the intermolecular forces of attraction in water (liquid) are not strong enough to hold the particles in a fixed position, unlike solids.

Explanation:

The ability to move through a substance depends on the strength of the forces between its particles and the available space (VspaceV_{space}).

Problem 3:

Calculate the density of a gas if a mass of 500 g500\text{ g} occupies a volume of 250 cm3250\text{ cm}^3.

Solution:

ρ=mVρ=500250ρ=2 g/cm3\begin{array}{r} \rho = \frac{m}{V} \\ \rho = \frac{500}{250} \\ \rho = 2\text{ g/cm}^3 \end{array}

Explanation:

Density measures how closely particles are packed within a given volume.