Separation Of Substances Class 6 Science Chapter 3 Notes

Separation of Substances Class 6 Science Chapter 3 Notes are available here. These notes have been carefully prepared by our subject experts, keeping in mind the guidelines set by NCERT. They include all the important information from the chapter in a simple and organised manner, making it easier for you to understand. You can freely download these user-friendly notes in PDF format from our website CBSE Wale. By studying and practising with these notes, you can enhance your knowledge and perform well in your exams to achieve excellent marks.

Separation of Substances Class 6 Science Chapter 3 Notes

Pure Substances

Pure substances have a uniform and consistent composition, meaning that every particle within the substance is the same.
They cannot be separated into other substances by physical means.
Pure substances can exist in different states of matter: solid, liquid, or gas.
Examples of pure substances include elements and compounds.
Elements are pure substances that are made up of only one type of atom. Some examples are oxygen, gold, and carbon.
Compounds are pure substances that are composed of two or more elements chemically combined in fixed proportions. For instance, water (H2O) is a compound made up of two hydrogen atoms and one oxygen atom.
Pure substances have distinct physical and chemical properties that are unique to the substance. These properties help identify and characterise the substance.

Impure Substances

Impure substances are also referred to as mixtures because they are a combination of different substances.
Unlike pure substances, impure substances do not have a uniform composition throughout. Instead, they contain different kinds of particles mixed together.
The substances in an impure substance can be physically separated from one another using various separation techniques.

Mixture

A mixture is formed when two or more substances are combined physically, without undergoing any chemical reactions. Here are some more details about mixtures:
In a mixture, each substance retains its own individual properties. This means that the substances in a mixture do not change chemically and can be separated by physical means.
Mixtures can be made up of elements, compounds, or both.
Mixtures can be separated into their individual components using various separation techniques, as we discussed earlier.

Separation

Separation is the process of separating different substances in a mixture.
It helps us obtain pure substances from impure substances.

Need of Separation

We need separation to remove unwanted substances or extract useful substances from a mixture.
It helps us get things like pure water, pure salt, or separate different types of grains.

Principle of Separation

The principle of separation is based on the properties of substances in a mixture.
Different methods of separation use these properties to separate the substances.

Methods of Separation

There are different methods of separation used depending on the properties of the substances.
Some common methods of separation are hand picking, threshing, winnowing, sieving, filtration, churning, sedimentation, decantation, condensation, evaporation, sublimation, and magnetism.

Hand Picking

Hand picking is the easiest way to separate things.
It’s like using your hands to pick out or remove larger particles from a mixture.
For example, if you have a mixture of rice and some stones,
You can just use your hands to pick out the stones one by one.
By looking and feeling the mixture, you can easily find and remove the bigger stones.
Once you’ve taken out all the stones, you’re left with just the rice.
Hand picking is as simple as picking things up with your hands.
It’s like when you pick up toys or choose your favourite candy from a bag.
So, with hand picking, you can separate larger particles by using your hands to pick them out from the mixture.

Threshing

Threshing is the process of separating grains from the stalks of plants.
It is done by beating the plants or using a machine called a thresher.
Example: Separating grains from wheat stalks.

Separation by Winnowing

Winnowing is a way to separate lighter particles from heavier particles using wind or blowing air.
Imagine you have a mixture of grains and husk.
To separate them, you can pour the mixture from a height in front of a fan or while blowing air gently.
As you do this, the lighter husk particles will be carried away by the wind or breeze.
Meanwhile, the heavier grains will fall down and separate from the husk.
This is how winnowing works – the wind blows away the lighter particles, leaving the heavier ones behind.
It’s like when you blow on a dandelion and the lighter seeds fly away.
By using winnowing, you can easily separate lighter particles from heavier particles using wind or blowing air.

Separation by Sieving

Sieving is a way to separate different-sized particles using a sieve.
A sieve is like a special strainer with tiny holes.
Imagine you have a mixture of sand and gravel that you want to separate.
You can use a sieve, which is like a small mesh screen.
Pour the mixture onto the sieve and gently shake it.
The smaller sand particles will fall through the holes of the sieve.
But the larger gravel particles will stay on top of the sieve.
This way, you can separate the sand from the gravel.
Sieving is like using a strainer to sort things by size.
It’s similar to when you use a strainer to drain water from pasta.
So, by using a sieve, we can separate particles of different sizes, with the smaller ones passing through the sieve while the larger ones stay on top.

Separation by Filtration

Filtration is a method we use to separate solid particles from a liquid using a filter.
A filter is like a sieve or a mesh that allows liquids to pass through but traps the solid particles.
Here’s how filtration works:
Imagine you have a cup of tea with tea leaves floating in it.
If you want to drink the tea without the leaves, you can use a tea strainer or a filter.
Pour the tea through the strainer or filter, and something interesting happens!
The liquid part of the tea, which is the tea itself, passes through the tiny holes or pores of the strainer.
But the solid tea leaves, which are the particles we want to separate, get trapped by the strainer.
As a result, you get a clear cup of tea without any tea leaves in it.
Filtration is like using a special sieve to separate the solid particles from the liquid.
It’s similar to how we sift flour to remove lumps or use a colander to drain pasta.
So, by using filtration, we can separate solid particles from a liquid by passing the liquid through a filter while trapping the solids.

Separation by Churning

Churning is a way to make butter from cream.
Cream is a thick liquid that has fat in it called butterfat.
To separate the butterfat from the cream, we need to shake it a lot.
Imagine pouring cream into a jar with a tight lid.
Shake the jar up and down or back and forth really hard.
As you shake the cream, something cool happens!
The fat in the cream sticks together and forms solid butter.
The butter clumps together and separates from the liquid part of the cream called buttermilk.
Then, you can pour out the buttermilk and rinse the butter to remove any leftover liquid.
What you have left is tasty homemade butter!
Churning is like giving the cream a good shake, and it helps separate the butter from the liquid cream.
So, by shaking cream really hard, we can separate the fat in it and make butter.

Separation by Sedimentation

Sedimentation helps us separate solid particles from a liquid.
When there are heavier particles in a liquid, they sink down to the bottom because of gravity.
Imagine you have muddy water with dirt in it.
If you leave the mixture alone, the dirt particles will slowly go down to the bottom of the container.
This is because the dirt is heavier than the water, so it settles down.
Once the dirt has settled, you can carefully pour off the clean water without disturbing the settled dirt.
It’s like when sand settles to the bottom of a jar of water.
By letting the heavier particles sink, we can separate them from the liquid.
So, sedimentation is a simple way to separate solid particles by letting them settle down while the liquid can be poured off.

Separation by Condensation

Condensation is when a gas or vapour turns into a liquid by getting cool.
Imagine taking a hot shower and noticing the steam on the bathroom mirror.
The steam is water vapour, which is a gas.
When the steam touches the cold mirror, it cools down and becomes water droplets.
It’s like the vapour turns into liquid water again.
This is called condensation because the vapour condenses or changes back into a liquid.
Similarly, we can use condensation to separate a gas or vapour from a liquid.
By cooling the gas or vapour, it turns into a liquid, and we can collect it separately.
So, condensation helps us separate a gas or vapour from a liquid by making it cool down and turn back into a liquid.

Separation by Decantation

Decantation is a way to separate a liquid from solid particles by pouring off the liquid carefully.
Imagine you have a glass of water with sand settled at the bottom.
To remove the water without disturbing the sand, tilt the glass slowly and pour the water out gently.
Make sure to pour it slowly so that the sand stays at the bottom.
By doing this, you can separate the water from the sand using decantation.
It’s like pouring water from a glass without stirring up the settled sand.
It’s similar to pouring juice from a carton while being careful not to let the pulp come out.
So, by using decantation, we can separate a liquid from solid particles by pouring off the liquid carefully, leaving the solid particles behind.

Separation by Evaporation

Evaporation is a process that allows us to separate a liquid from solid particles by heating it until it changes into a gas or vapour.
When a liquid is heated, its molecules gain energy and become more active.
Eventually, some of the liquid molecules at the surface gain enough energy to escape into the air as gas or vapour.
As these liquid molecules escape, the liquid slowly dries up and eventually evaporates completely.
Here’s an example of how evaporation can be used to separate a liquid from solid particles:
Imagine you have a wet towel that you want to dry.
If you leave the towel out in the sun, the heat from the sun will increase the temperature of the water in the towel.
As a result, the water molecules in the towel gain energy and start to evaporate.
Over time, the liquid water evaporates into the air, leaving behind the solid particles, such as dirt or salt, that were mixed with the water.
This happens because the water molecules can escape into the air as vapour, while the solid particles remain behind.
Evaporation is a natural process that occurs when a liquid is heated, and it is commonly used to separate liquids from solid particles.
So, by using evaporation, we can separate a liquid from solid particles by heating it until it turns into a gas or vapour, leaving behind the solid particles.

Separation by Sublimation

Sublimation is a unique process that allows us to separate a solid from a mixture by heating it.
Normally, when we heat a solid, it melts and changes into a liquid. But in sublimation, something different happens.
When a solid undergoes sublimation, it changes directly from a solid to a gas without becoming a liquid in between.
This means the solid turns into vapour without going through the liquid stage.
Here’s an example of how sublimation can be used to separate a solid from a mixture:
Let’s consider a mixture that contains iodine crystals and some other substances.
By heating the mixture gently, the iodine crystals will start to sublimate.
As they heat up, they change directly from solid to vapour without becoming a liquid.
The vaporised iodine can be collected separately, leaving behind the other substances in the mixture.
Once the vapour cools down, it can condense back into solid iodine.
Sublimation is a useful method for separating solids that have the property of sublimation from other substances that do not sublimate.
So, by using sublimation, we can separate the solid component of a mixture by heating it and collecting the vapour.

Separation by Magnet

Magnetism is a special property that some substances have.
It allows us to separate magnetic substances from non-magnetic substances using a magnet.
Magnetic substances are materials that are attracted to a magnet, like iron or steel.
Non-magnetic substances are materials that are not attracted to a magnet, like plastic or wood.
Here’s an example of how we can use a magnet to separate a mixture:
Let’s say we have a mixture of iron nails and other non-magnetic objects like plastic beads.
By moving a magnet over the mixture, the iron nails will be attracted to the magnet and stick to it.
We can lift the magnet, and the iron nails will come along, while the non-magnetic objects will stay behind.
This separation works because the magnetic force pulls the iron nails towards the magnet.
It’s like a magnet “catching” the nails while leaving the other objects behind.
So, using a magnet is a handy way to separate magnetic substances from a mixture of materials that are not magnetic.

Solutions

Solutions are special mixtures where one substance completely dissolves in another substance.
When we mix two things together to make a solution, one of them is called the solute, and the other is called the solvent.
The solute is the substance that dissolves, and the solvent is the substance that does the dissolving.
For example, let’s think about making saltwater by mixing salt and water.
In this case, salt is the solute because it’s the substance that dissolves.
Water is the solvent because it’s the substance that does the dissolving.
When we stir the salt in water, the salt particles spread out and mix with the water particles until they can’t be seen anymore.
The result is a solution called saltwater, where the salt is dissolved in the water.
Solutions can be made with many different substances, not just salt and water.
So, remember, a solution is a mixture where one substance (solute) dissolves completely in another substance (solvent).

Saturated Solution

Sometimes when we make a solution, we can reach a point where no more solute can dissolve.
This is called a saturated solution.
Imagine you’re making a cup of tea and you add sugar to it.
As you stir the tea, the sugar dissolves and mixes with the tea.
But if you keep adding more and more sugar and stirring, there comes a point where the tea can’t dissolve any more sugar.
This means the solution is saturated, and any extra sugar you add won’t dissolve.
Instead, it will settle at the bottom of the cup.
It’s like when you pour water into a glass until it’s completely full, and if you keep pouring, the water will spill over.
So, a saturated solution is when no more solute can dissolve at a given temperature, and any excess solute settles at the bottom.

Unsaturated Solutions

Sometimes we want to mix things together to make a solution.
An unsaturated solution is when we can still add more of something to the solution.
For example, let’s think about making a cup of tea with sugar.
When we add a small amount of sugar to the hot tea and stir it, the sugar dissolves completely.
This means the tea is an unsaturated solution because we can still add more sugar if we want.
If we keep adding sugar and stirring, eventually the tea might become saturated, which means no more sugar can dissolve in it.
It’s like a sponge that can soak up more water until it can’t hold any more.
So, remember, in an unsaturated solution, more solute (like sugar) can still dissolve at a given temperature.