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Particulate Nature of Matter - Liquid state

Grade 8CBSE

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

🔑Concepts

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Liquids have a definite volume but no definite shape; they take the shape of the container they are placed in.

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The intermolecular forces of attraction in liquids are weaker than in solids but stronger than in gases.

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Particles in a liquid have more kinetic energy than those in solids, allowing them to slide past each other, which is why liquids possess the property of fluidity.

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The intermolecular spaces in liquids are slightly larger than in solids, making them slightly more compressible than solids, though still considered incompressible for most practical purposes.

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The rate of diffusion in liquids is higher than in solids because particles move freely; for example, KMnO4KMnO_4 crystals dissolving in water.

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Density of liquids is generally lower than solids: Density=MassVolume\text{Density} = \frac{\text{Mass}}{\text{Volume}}.

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Evaporation is a surface phenomenon where liquid particles gain enough kinetic energy to overcome intermolecular forces and change into vapor at temperatures below the boiling point.

📐Formulae

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

T(K)=T(∘C)+273T(K) = T(^{\circ}C) + 273

Rate of Diffusion∝Temperature\text{Rate of Diffusion} \propto \text{Temperature}

💡Examples

Problem 1:

A liquid occupies a volume of 250 cm3250\text{ cm}^3 and has a mass of 200 g200\text{ g}. Calculate the density of the liquid.

Solution:

ρ=200 g250 cm3=0.8 g/cm3\rho = \frac{200\text{ g}}{250\text{ cm}^3} = 0.8\text{ g/cm}^3

Explanation:

Density is the ratio of mass to volume. By dividing the mass (200 g200\text{ g}) by the volume (250 cm3250\text{ cm}^3), we find the density is 0.8 g/cm30.8\text{ g/cm}^3.

Problem 2:

Convert the boiling point of water, 100∘C100^{\circ}C, into the Kelvin scale.

Solution:

T(K)=100+273=373 KT(K) = 100 + 273 = 373\text{ K}

Explanation:

To convert Celsius to Kelvin, we add 273273 to the temperature in Celsius.

Problem 3:

The mass of a beaker filled with water is 545 g545\text{ g}. If the mass of the empty beaker is 125 g125\text{ g}, find the mass of the water using vertical subtraction.

Solution:

545−125420\begin{array}{r} 545 \\ - 125 \\ \hline 420 \end{array}

Explanation:

To find the mass of the liquid, subtract the mass of the container (empty beaker) from the total mass (beaker + liquid). The mass of the water is 420 g420\text{ g}.

Liquid state Class 8 Notes & Examples | CBSE Science