Is Matter Around Us Pure Class 9 Notes Science - Chapter 2
What Are Is Matter Around Us Pure?
Anything that cannot be broken into further particles by applying any physical processes is called a Substance. Matter can be classified into two types of substances – Pure substances and Mixture
Types of Pure Substances
- Cannot be broken down to simpler substances. For example, copper , oxygen , iron , hydrogen , mercury , etc.
- Have fixed composition, can be broken down into elements by chemical or electrochemical reactions. For example, water , methane , sugar , salt , etc.
When different substances are combined with each other a mixture is formed. For Example, Lemonade is a mixture of three substances, Lemon Juice, Sugar and Water.
Types of Mixtures
• Homogeneous Mixture: A mixture having a uniform composition throughout is called a homogeneous mixtures or solutions.
• We cannot separate the components of the mixture through physical processes.
Example: Petrol , Vinegar and Soft drinks.
• Heterogeneous mixture: A mixture which contain physically distinct parts and have non-uniform composition is called a heterogeneous mixtures.
• We can separate the components through physical processes.
Example: Mixtures of sodium chloride and iron filings, salt and sulphur, oil and water, and paint.
• Particles of matter attract each other.
A solution is a homogeneous mixture of two or more substances.
Solvent: The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent.
Solute: The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.
Example: A solution of sugar in water is a solid in liquid solution. In this solution, sugar is the solute and water is the solvent.
Properties of a Solution
• A solution is a homogeneous mixture.
• Due to very small particle size, they do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.
• The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.
Types of Solution
• Dilute Solution: A solution in which the concentration of the solute is much less than that of the solvent.
• Concentrated Solution: A solution with a large amount of solvent is called a Concentrated Solution.
• Saturated Solution: When no more solute can be dissolved in a solution at a given temperature, it is called a saturated solution.
• Unsaturated Solution: If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.
• Solubility: The amount of the solute present in the saturated solution at this temperature is called its solubility.
Concentration of a Solution
The concentration of a solution is the amount of solute present in a given amount (mass or volume) of solution, or the amount of solute dissolved in a given mass or volume of solvent.
Concentration of solution = Amount of solute/Amount of solution
Amount of solution = Amount of solute + Amount of solvent
Ways of Expressing the Concentration of a Solution
• Percent by Mass = (Mass of solute / Mass of solution) × 100
• Percent by Volume = (Volume of solute / Volume of solution) × 100
• Molarity (M) = Number of moles of solute / Volume of Solution in litres
• Normality (N) = Number of mole equivalents/ volume of solution in litres
A colloidal solution or a colloid is a heterogenous solution of two or more substances.
• Dispersed Phase: The solute-like component or the dispersed particles in a colloid form the dispersed phase.
• Dispersion Medium: The component in which the dispersed phase is suspended is known as the dispersing medium.
Properties of a Colloids
• A colloid is a heterogeneous mixture.
• The size of particles of a colloid is very small.
• Colloids are big enough to scatter a beam of light passing through it and make its path visible. This is called Tyndall Effect.
• A colloid is quite stable.
• A special technique of separation known as centrifugation can be used to separate the colloidal particles.
Types of Colloids
On the basis of dispersed phase and dispersion medium
|Dispersed phase||Dispersing Medium||Type||Example|
|Liquid||Gas||Aerosol||Fog, mist, clouds|
|Solid||Gas||Aerosol||Automobile exhaust, smoke|
|Liquid||Liquid||Emulsion||Milk, Face cream|
|Solid||Liquid||Sol||Milk of magnesia, mud|
|Gas||Solid||Foam||Foam, rubber, pumice, sponge|
|Liquid||Solid||Gel||Cheese, butter, jelly|
|Solid||Solid||Solid Sol||Coloured gemstone, milky glass|
A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium.
Properties of a Suspension
• Suspension is a heterogeneous mixture.
• The particles of a suspension can be seen by the naked eye.
• The particles of a suspension scatter a beam of light passing through it and make its path visible.
• A suspension is unstable.
Physical And Chemical Changes
These changes occur without a change in composition and no change in the chemical nature of the substance. Example: conversion of ice to water or water vapour.
These changes occur without a change in composition and no change in the chemical nature of the substance. Example: Burning