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Particulate Nature of Matter - Solid state

Grade 8CBSE

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

🔑Concepts

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Matter is composed of tiny particles which are either atoms or molecules.

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In the solid state, particles are very closely packed with negligible intermolecular spaces.

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The intermolecular force of attraction in solids is very strong, which keeps the particles in fixed positions.

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Particles in a solid do not have translational motion; they only vibrate about their fixed mean positionsmean \ positions.

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Solids possess a definite shape, distinct boundaries, and a fixed volume.

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Solids are characterized by high density and are generally incompressible due to the lack of space between particles.

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The kinetic energy of particles in a solid is the minimum compared to liquids and gases.

📐Formulae

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

Volume of a Cube(V)=a3\text{Volume of a Cube} (V) = a^3

Intermolecular Force∝1Intermolecular Space\text{Intermolecular Force} \propto \frac{1}{\text{Intermolecular Space}}

💡Examples

Problem 1:

A solid rectangular block of iron has a mass of 7800 g7800\ g and a volume of 1000 cm31000\ cm^3. Calculate its density in g/cm3g/cm^3.

Solution:

Density=7800 g1000 cm3=7.8 g/cm3\text{Density} = \frac{7800\ g}{1000\ cm^3} = 7.8\ g/cm^3

Explanation:

Density is defined as mass per unit volume. By dividing the given mass by the volume, we find the density of the iron block.

Problem 2:

Calculate the volume of a solid wooden cube if its mass is 400 g400\ g and its density is 0.8 g/cm30.8\ g/cm^3.

Solution:

V=md=4000.8=500 cm3V = \frac{m}{d} = \frac{400}{0.8} = 500\ cm^3

Explanation:

Using the rearranged density formula V=mdV = \frac{m}{d}, we substitute the given values to find the volume occupied by the solid particles.

Problem 3:

Why does a solid piece of iron not change its shape when moved from a table to a floor?

Solution:

Due to strong intermolecular forces and fixed particle positions.

Explanation:

In solids, the particles are held together by very strong forces of attraction. They are tightly packed in a rigid lattice, meaning they cannot slide over one another. Thus, the shape remains constant regardless of the container or position.

Solid state Class 8 Notes & Examples | CBSE Science