Class 6 Science Chapter 2 ‘Sorting Materials Into Groups’ Notes by Sciक्षक

Before starting with Class 6 Science Chapter 2 i.e. ‘Sorting Materials Into Groups’, I am hoping that you have completed the 1st chapter. If not, then you can go through its Notes and NCERT Exercise Solutions whose links have been provided below. ⤵️

Table of Content

Introduction

To understand this chapter thoroughly we have to first learn about the sensory organs and various characteristics that can be perceived with them.

Sensory Organs and Observable Traits or Characteristics

The name ‘sense organs‘ has its meaning inherent to itself. They are the organs through which we sense our surroundings. There are mainly 5 sense organs that we all have.

1. Eyes
2. Ears
3. Nose
4. Tongue
5. Skin

The various observable traits that can be perceived through our sense organs are:

Now that we have gotten ourselves familiar with this concept let’s dive into the chapter.

What is sorting?

It means grouping things together on the basis of their common characteristics or traits.

e.g. students of class 6 sit together in one classroom because they all are class 6 students and class 7 students sit together likewise.

Objects Around Us

We are surrounded by a vast variety of objects and human beings. In the last chapter, we have learned about the variety of food items that we consume. If you look around in your classroom you will be able to list a whole lot of things e.g. walls, paint, classmates, school dress, backpack, notebooks, chalk, teacher, duster, fans, lights, etc.

Now you will be able to sort them out on the basis of different traits like color, shape, length, texture, etc.

An object can be made up of only one kind of material e.g. chalk or different kinds of materials as well e.g. your pencil (wood, graphite, etc.)

One material can be used for making different kinds of objects. For example, from paper, we can make notebooks, cups, fans, caps, carry bags, etc.

Now that we have learned this much about objects and materials.

Let’s play a small game-

Game: Name any 10 objects that can made from plastic.

What is an object?

An object is something physical (perceivable through our sense organs) that is made from material(s) and has a specific use.

e.g. Block of raw iron as a material is useless for you as a student but once it is moulded into a chair it is useful for you. So, here the object is the Chair and the material is Iron.

But, what decides which material should be used for making any given object?

Properties of Materials

Before answering the last question, first answer this simple question.

Que: Can we make a frying pan with paper instead of iron?

We can’t because a frying pan made with paper will catch fire when it comes in contact with a stove fire and burn itself rather than cooking food.

So, we choose a material(s) to make a particular object depending on its properties and the purpose for which the object will be used.

So, in the above example, the purpose of our object (frying pan) is to fry something or to heat something, and the properties that the material(s) should have are good heat conduction, not getting burned by fire itself, etc.

Some of the common characteristics possessed by various materials are-

1. Appearance

It means how something looks or seems to appear.

Appearance includes characteristics like color, shape, size, lustre, etc.

Collect some samples of different materials that you use in your daily life as a student e.g. pen, pencil, rubber, pencil sharpener, notebooks, ruler (plastic or metallic), divider, paper pin, bench, table, etc. Now, look at them clearly under sunlight.

You will notice some materials shine in light while some don’t.

Materials that usually shine in light are metals.

You can take an iron nail and if it is corroded or rusted then rub it with sandpaper and you will see a shiny iron surface once you have cleaned its surface with sandpaper or cut it into two halves.

Some metals lose their shine or lustre and appear dull, because of the action of water (moisture) and air, this is known as the corrosion of metal.

2. Hardness

Collect a few objects like iron nails, sponges, rubber, etc., and try to pinch or compress them with your hands. You will observe that some objects get easily compressed while some don’t.

You will observe that materials that can be compressed can be easily scratched as well.

So, the materials which can be easily scratched and compressed are called soft.

And, the materials which are difficult to scratch and compress are called hard.

3. Solubility

Is the ability of a substance to dissolve in water.

Substances that get completely dissolved in water are called soluble. e.g. sugar, salt, vinegar, etc.

Substances that do not mix with water and do not dissolve even after stirring are called insoluble. e.g. chalk powder, sawdust, dust, dirt, oil, etc.

Insoluble liquids like coconut oil, kerosene, etc. form a layer over water.

Some gases are also soluble in water as well e.g. oxygen dissolved in water is used by animals and plants living in the water. Carbon dioxide gas is dissolved in water in carbonated drinks like Coca-Cola, Pepsi, etc.

4. Density

It is the mass in kilograms of 1000 m3 of the substances. In simple words, it means the mass of equal volume of substances.

Explanation: I) Take an empty 1L bottle and fill it with water, then weigh it and note down its mass/weight.

II) Now empty the bottle again, dry it and fill it with sand this time, weigh it and note down the measurement.

III) This time empty the bottle and fill it with oil (mustard oil), weigh it, and note down its measurement.

Now, take a large clean beaker and fill it half with water. Then, add the sand that we weighed and oil into it, stir it, and let it settle.

You will notice that sand has settled into the bottom of the beaker and oil is floating over the water.

Why is it happening?

Some substances float on water, whereas some sink.

Substances whose density is less than water will float. And substances whose density is more than water will sink.

That is why oil is floating on water and sand sunk into the bottom.

5. Transparency

It is the ability of an object to let the light pass through itself.

Activity: I) Take a notebook, page, glass, and torch.

II) Switch on the torch put the notebook in front of its glass and see whether the light is passing through the notebook. and repeat the same for a page and a glass.

Substances that allow light to pass through them completely are called transparent.

Substances that don’t allow light to pass through them are called opaque.

Substances that partially allow the light to pass through them are called translucent.

Fun Fact: No object is 100% transparent.

Conclusion

Sorting of materials and objects into groups makes it convenient to study their properties and also observe any patterns in these properties. We do sorting for convenience in our daily life as well.

References & Credits

• Class 6 Science NCERT Textbook.
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