is matter around us pure- chapter 2, pure substance and mixtures

NATURE OF MATTER-SCIENCE- CBSE-STUDY MATERIAL- PART-1-IS MATTER AROUND US PURE CLASS 9

is matter around us pure class 9

In our daily life, we come across different types of substances and we are considering some among them as pure substances. Are they actually pure? 

What are the conditions for a substance to be pure? 

We can classify matter into two types based on its chemical composition.

1.Pure substances

2.Mixtures

PURE SUBSTANCE - Substances that consist of a single type of particles are said to be pure.

Example- A piece of gold is said to be pure if it contains only gold particles in it.

gold nugget

MIXTURES - substances that contain more than one substance mixed in any proportion. Mixtures are not having any fixed composition.

 Mixtures can be separated into pure substances by using separation techniques.

Example- Solution of salt and water, oil in water

oil in water

TYPES OF PURE SUBSTANCES 

Pure substances can be classified into two types based on their chemical composition:

1. Element

2. Compounds

ELEMENT- Elements are pure substances that can not be broken down into simpler substances by chemical reactions.

Example- Iron, Oxygen, Hydrogen, Mercury, Gold.

All the known elements are arranged in a table called the periodic table in which the symbol and its basic information are given.

periodic table

Elements can be classified into three:

• metals
• non-metals
• metalloids

METALS- Iron, Copper, Gold, Silver, Mercury, Sodium, Magnesium.

SILVER & GOLD

Properties of metals:

• Metals are lustrous
• They conduct electricity and heat
• They are malleable
• They are ductile
• They are sonorous
• They have mostly silvery-grey or golden yellow color.
• Most of the metals are solids, except Mercury(liquid).

NON-METALS- Hydrogen, Oxygen, Nitrogen, Carbon, Sulphur, Chlorine, etc.

Bromine is a liquid non-metal.

SULFUR

Properties of non-metals:

• Non-metals are non-lustrous
• They are not malleable
• They are not ductile
• They are poor conductors of electricity and heat
• They display different types of colors
• They are non-sonorous

COMPOUND- These are substances in which two or more elements combined in a fixed proportion.

Example- Water ((H2O), Carbon dioxide (CO2), Iron sulfide (FeS)

• Elements of different elements can combine to form compounds.
• The substance formed is entirely different in its properties.
• The new substance formed has a fixed composition.
• The constituents present in a compound can be separated by chemical or electrochemical methods.

TYPES OF MIXTURES

Based on the nature of the components that form a mixture, there are two types of mixtures. They are:

• Homogeneous mixtures
• Heterogeneous mixtures

 Homogeneous mixtures- A mixture that has a uniform composition throughout.

Example- Sugar in water, salt in water, copper sulfate in water.

HOMOGENEOUS SOLUTION

Heterogeneous mixtures -A mixture that has a non- uniform composition. It has physically distinct particles.

Example - a mixture of sand and salt, the mixture of oil and water, the mixture of salt and iron filings.

MIXTURE OF SEEDS

SOLUTION

Solute + Solvent = Solution

The component of the solution which dissolves the other component in it is called the solvent.

The component that is dissolved in the solvent is called the solute.

In tincture iodine, iodine is the solute that is dissolved in solvent alcohol. In soda, carbon dioxide is the solute and water is the solvent.

A solution is a mixture of two or more components. We come across different types of solutions in our life like lemonade, soda, salt solution, etc. 

By mixing the three states of matter solid, liquid, or gas in different proportions, a solution can be made. 

There are solid-solid solutions like alloys in which different metals or one metal with a non-metal is mixed.

We can classify solutions into three types:

• True solution
• Colloids
• Suspension

PROPERTIES OF A TRUE SOLUTION

• It is a homogeneous mixture.
• The particle size is less than 1 nanometer in diameter.
• Particles in a solution can not be seen by naked eyes.
• They do not show the Tyndall effect-do not scatter a beam of light passing through the solution.
• Particles can not be separated by filtration.
• The solution is stable- the particles do not settle down.

Example - salt solution, copper sulfate solution.

True solution

PROPERTIES OF A COLLOIDS

• A colloid is a heterogeneous mixture.
• The particle size is 1-100 nanometer in diameter.
• Particles in the solution can not be seen by naked eyes.
• They show Tyndall effect-
• particles are big enough to scatter a beam of light passing through the solution and make the path visible.
• It is stable- the particles do not settle down when left undisturbed.
• Particles can not be separated by filtration. But can be separated by centrifugation.

Examples of colloids- Milk, fog, smoke, foam, jelly.

Milk- colloid

The main types of colloids are aerosol, foam, emulsion, sol, gel, and solid sol.

Like solute and solvent, the components in a colloid are called a dispersed phase and a dispersion medium.

The dispersed particles in a colloid are called the dispersed phase and the component in which the dispersed phase is suspended is called the dispersion medium.

Example- in fog, water particles are dispersed phase and the air is the dispersion medium.

Fog- colloid

TYNDALL EFFECT

It is the process of scattering of a beam of light by the small particles like colloidal particles. 

The Tyndall effect can be observed when a beam of light enters a room through a window or small hole, where dust particles present in air scatters light.

 

Similar is the case with the beam of sunlight in a canopy. In the forest, tiny droplets of water in the mist acts as the colloidal particles in the air.

Mist-Tyndall effect

PROPERTIES OF SUSPENSION

• The particle size is more than 100 nm.
• It is a heterogeneous mixture.
• The particles can be seen by our naked eye.
• The particles can scatter a beam of light passing through it and make its path visible. But when particles settle down, it cannot scatter light and can not show the Tyndall effect.
• It is unstable- particles settle down.
• Can be separated by filtration.

Example- Chalk powder in water, sand, and water