Matter Around Us

Class 6 | Science — Chemistry | Unit 3

Class 6 Unit 3 Science

Unit 3 Matter around us

Learning Objectives

• To define matter and develop an understanding on the particle nature of matter.
• To sort the objects on the basis of certain properties.
• To differentiate solids, liquids and gases based on the arrangement of their particles.
• To differentiate pure substances from mixtures.
• To identify the need for separation of mixtures.
• To suggest suitable methods for separating given samples of mixtures.
• To acquire an awareness on food adulteration and its harmful effects.

Introduction

Matter is everywhere around us. The air we breathe, water we drink and the material we use are made up of matter. Matter is defined as anything that occupies space and has mass. Matter is found in three major states: solid, liquid and gas. Do you know what is matter made of? Matter is made of atoms. Atoms are the smallest particle of matter. They are so small that you cannot see them with your eyes or even with a standard microscope. A standard sheet of paper is about millions of atoms thick. Science has come up with a technology to identify the structure of atoms by using atomic resolution Microscope (A R M) and Tunnelling Electron Microscope (T E M) which use electricity to map atoms. There is more about atoms in the later classes. But first let's learn about the three states of matter.

3.1 Physical Nature of Matter

Matter occupies space and has mass. What is its nature? Many philosophers pondered over this question and came out with ideas. Imagine that a piece of thread is cut endlessly using knife. At one point it would be like a small piece that it cannot be further cut by a knife. That small particle may contain millions of molecules and these molecules are made of atoms. Matter is made of such smallest particles 'atoms'. These atoms are extremely small even to see under a powerful microscope.

Activity 1

Take a few crystals of sugar. Observe them carefully with the help of a magnifying lens. Which of the shapes given above resemble a sugar crystal? A B C D E F

Now place a few sugar crystals into water. What happens to the sugar crystals?

A sugar crystal is also made up of molecules. When sugar dissolves in water, the sugar crystals break down and the molecules of sugar get distributed in water. This makes water sweet in taste. The sugar molecules are extremely small; that is why we are not able to see them. Small amount of matter has many millions of molecules in it (1 million = 10 lakhs).

Characteristics of the particles of matter

1. Particles of matter have a lot of space in between them. In different forms of matter this spacing will be different. Let us add a spoon full of sugar to a glass of water. Stir well. Sugar disappears completely. Where has it gone? Will the glass of water be now sweet? Water particles have space between them and sugar particles are now occupying those spaces.

2. Particles of matter attract each other. It is the force of attraction which keeps the particles together. This attractive force will be different for different forms of matter.

Grouping of Matter on the basis of Physical states

These are the three physical states of matter. Matter can be grouped into solids, liquids and gases based on the above characteristics.

3.2 Mass, Shape and Volume of Solids, Liquids and Gases

Let us first take any solid say a stone: Answer the following questions.

Do you need a container to know the shape of a stone?

A solid does not need a container. It stays as it is because its particles are tightly packed and has a definite shape.

If you move the stone from the ground to a table or place it on the shelf does it's shape change?

If you take a stone from the ground and place it on the table or shelf its shape and volume do not change.

Activity 2

Sit together in groups of three. Look at the objects given below. Are they familiar to you? Are the same or different? On what basis you can group them? Is there only one way of doing it or more ways? Discuss with your group members and note down your points.

Pencil and books are used for studying. The bucket and the comb are made of plastic while the table and ladle are made of wood. The scrub brush and broom are rough but the toy bear is soft. Light can pass through a glass of water and the spectacles but not through apple or iron box. The cow and the bird are living things while the rest are not. Water in the glass is liquid but air in the balloon is gas and the rest are solids. The feather and the paper cup can float but not the apple or the piece of stone. The rubber band can be stretched but not the comb. Though they have different properties, they are matter.

Exercise Try to fill in the following table

You can group them according to their uses, the materials with which they are made of or some other properties.

Serial number	Things that float	Things that sink
1
2
3

Try to make more such tables based on the properties discussed above. How many tables could you make? How did you classify the items in the above list as solids, liquids and gases? You should have done it based on some properties. Brick and door which are hard come under solids, things that flow come under liquids and others which are very light and can flow more freely come under gases.

Activity 3

Malar was asked to group some items based on their physical states. The table she made is given below. Do you agree with her? Correct the table if you do not agree and submit it to your teacher. (Work in a group of two.)

Solids	Liquids	Gases
Chalk piece	Water	Wind

Items given: Steam, Rain, Lemon, Air in a balloon, Stone, Lemon juice, River, Air, Smoke, Brick, Table, door

3.3 Diffusion

Let us place a book on a table. Let it not be disturbed. Observe for five minutes. Now take a glass of water and add a drop of ink carefully at the centre. Do not shake or stir. Now light an incense stick and keep it in one corner of the room.

Exercise Let us answer the following questions

• Did the book move?

• Did the ink particles move and spread itself in the water? How long did it take for complete mixing?

• Did you get the smell of the incense stick from where you are standing?

• How fast did you get the smell? How did the smell reach you?

We may conclude that the particles of gases and liquids can move easily and quickly. This tendency of particles to spread out in order to occupy the available space is called diffusion. Solids are tightly packed and they do not diffuse like liquids or gases. Hence ink and smoke spread easily while book stays on the table.

Particles in different states

Particles in a Solid: In solid, the particles are tightly packed with very little space between them. Example. Stone

Particles in a Liquid: Particles in liquids are arranged in a random or irregular way and the space between the particles is greater than that is in solids. Example. Water

Particles in a Gas: The particles in the gases are arranged far apart. They move freely. Example. Air

Activity 4

Let us take two sachets of juice. In both the sachets, it is written 100ml. Let us empty two sachets and pour the juice into the following glasses.

Does its shape change?

A liquid needs a container and it takes the shape of a container because the particles slide over one another and keep moving.

Does its volume change when it is poured into a big glass as well as a small one?

The amount of juice is the same in both glasses. How will you find out whether the volume has changed or not?

The volume of a liquid remains the same whether it is kept in a large container or a small one but its shape changes.

Activity 5

Lift an uninflated cycle tube. Inflate it and now lift it again. Is there a change in the weight? Can we say that air has mass? We can say that air is also a matter. Though we cannot see it, it occupies space and also has mass. Let us try to know more about matter.

Test yourself

1. Name an object which is brittle and transparent .

2. Name an object which can be stretched .

3. Name two objects which can be bent .

3.4 Compressibility of gases compared to liquids and solids

Let us take three identical syringes. Close the nozzles tightly with a cork. After removing the plunger first let us fill it with fine chalk powder. Try to press plunger down. What do you observe? Now let us fill the second one with water. Press the plunger down. What do you observe? Let us now draw the piston back to suck air into the third one. Press the plunger down. What do you observe? Is it easy or hard to press? Record your observations and share among the group members.

Exercise Record your observations

Syringe with	Observation
Chalk powder
Water
Air

You would have observed that the plunger moved freely in syringe with air than in water. It was difficult to press the liquids and the piston hardly moved in chalk powder. Thus, we can conclude that gases are highly compressible as compared to liquids and solids.

Think to learn

Liquefaction of gases' is the process by which substances in their gaseous state are converted to the liquid state. When the pressure on a gas is increased, its molecules come closer together, and the temperature is reduced. This removes enough energy to make it change from the gaseous state to the liquid state.

Lets summarize

Serial number	Solids	Liquids	Gas
1	Solids have definite shape and volume	Liquids have no definite shape. Liquids attain the shape of the vessel in which they are kept.	Gases have neither a definite shape nor a definite volume.
2	Solids are incompressible	Liquids can compressible to a small extent.	Gases are highly compressible
3	There is little space between solid particles. Particles are tightly packed or arranged.	Liquid particles have a greater space between them. Particles are not tightly packed or arranged. They are free to move.	The space between gas particles is the greatest. Particles are very loosely packed or arranged.
4	Solid particles attract each other very strongly.	The force of attraction between liquid particles is less than solid particles.	The force of attraction is least between gaseous particles.
5	Particles of solid cannot move freely.	These particles move freely.	Gaseous particles are in a continuous, random motion.

3.5 Pure Substances and Mixtures

In shops, we find products which are sold with label 100% pure! For common people pure means unadulterated, does not contain any cheap or harmful additives. Are they really pure substances as they claim to be? For a Chemist the word 'pure' means something else! A pure substance is made up of only one kind of particles. Pure substances may be elements or compounds. An element is made up of same kind of atoms. A molecule consists of two or more atoms. Compound is the substance formed by the chemical combination of two or more elements. Mixture is a physical combination of two are more substances.

Let us consider the following examples. We all eat snacks. Can you identify and mention a few things that are present in a mixture or fruit mixture? You are able to identify the ingredients in them from their colours, appearance or taste. We mix rice, dal, salt, chillies, pepper, ghee and other ingredients to make pongal. Pongal is also an example for mixture. Why do we call these as mixtures? Because they are made of two or more ingredients or components that are physically separable.

Explore

Can we always see the different components of the mixture with our naked eyes? Let us compare the vegetable salad and soda water. In vegetable salad the individual vegetable can be separated physically. In soda water we can neither see nor separate the components physically.

Exercise Try it yourself

Identify the mixture given in the table below. Write 'yes' for a mixture and 'no' if it is not a mixture. You may also write 'I do not know' and later discuss with your teacher.

Mixture	Yes or No
Borewell water
Copper wire
Sugar cube
Salt Solution

Air is a mixture because it contains oxygen, nitrogen, carbon dioxide, water vapour, noble gases and other gases. Milk is also a mixture. It contains water, fat, protein etc. Lemon juice is a mixture. Some of us like to have it with less sugar; while others like to have it with more sugar. But either way, it is still lemon juice - prepared from lemon extract, water and sugar and is a mixture though the amount of sugar added is different. Same way even if we add extra water or lemon extract it will still be a mixture. A mixture need not have a fixed proportion of components.

Key Points about Mixtures

• A mixture is an impure substance and contains more than one kind of particles.

• In the mixture the components are mixed in any proportion.

A mixture can be a physical combination of two or more elements. Example: 22 carat gold which is composed of gold and copper or gold and cadmium.

It can be a physical combination of two or more compounds. Example: Aerated drink which is composed of carbon dioxide, water, sweetening and colouring agents.

It can be a physical combination of an element and a compound. Example: Tincture of iodine is composed of Iodine in alcohol.

3.6 Separation of Mixtures

Are all mixtures used as they are? Or is there a need for separating the components? Materials we use in our day- to-day life are got from different sources and are very often combined with other substances. Mixtures like coffee and ice cream are taken as such. There is no need for separation of this substances. Metals occur in the form of ores under the earth's crust. But if we want to use a pure metal, we need to adopt a laborious process of extraction to separate the useful metal from the ore. what is meant by separation? The process by which the components of mixture are isolated and removed from each other to get pure substance is called separation.

When and why do we need to separate mixtures?

• When we need to remove impurities or harmful components from the mixtures. Example. Stones from rice.

• When the useful component has to be separated from other components. Example. Petrol from petroleum.

• When a substance has to be obtained in highly pure form. Example. Gold from gold mines.

Let us visit Selvi's Family

It is 7 am and Selvi's family is busy. At home, in the kitchen, Selvi's mother is making tea for the family and her grandmother is separating butter from curds. Her father and uncle are out in the field collecting paddy after harvesting. Selvi is helping her mother to cook rice and is separating stones from the rice. Selvi's little brother Balu is fascinated by a piece of magnet that was given by his friend and is playing outside in the sand with it.

Exercise List the activities

Can you list out in your note book, the different activities that Selvi's family members are engaged in?

Let us explore the different separating methods involved in the above activities and also learn about a few other methods. The choice of the method of separation depends upon the properties of the components of the mixture. The separation method may be based on the particle's size, shape or physical state – solids, liquids or gases.

Filtering

Selvi's mother used a strainer to remove the tea leaves to get the clear liquid. Larger sized particles of tea leaves will be retained by the strainer while the clear liquid will pass through. This is called filtering. Will you discard the tea leaves after straining? Can you suggest a good way of using them?

Sieving

A sieve is similar to a strainer. Sieving is used when we have to separate solid particles of different sizes. Example: bran from flour, sand from gravel etc. Wire mesh as a strainer sieve is used to separate gravel from sand at a construction site.

Activity 6

Think and find, is it a good idea to separate bran from flour?

Churning

When very fine insoluble solids have to be separated from a liquid as in butter from curd, churning is performed. The mixture is churned vigorously when solid butter will be collected on the sides of the vessel. Both butter and butter milk obtained after churning are useful and can be consumed.

Do You Know?

In washing machines water is squeezed out from clothes and they are dried. This method is called centrifugation.

Threshing

When we pluck flowers from plants, we are separating the flowers from their stalks. Can we do the same for food grains like rice and wheat? It is not possible because the grains are small in size and also the quantity is very large. Farmers separate grains from their stalks by beating them hard. The grains are separated from their stalks. This is called Threshing.

Winnowing

Rice, wheat and other food grains are covered with husk which cannot be eaten by us. Husk is very light and gets easily blown away by a breeze or wind. The method used for removing husk from grain is called winnowing. This is done by dropping the mixture slowly from a height in the presence of wind. Lighter solids that is husks will be carried by wind and will be collected in a separate heap while heavier solids that is grains will fall closer and form a separate heap.

Do You Know?

Rice husk also called chaff is the hard coating or protective covering on a seed or grains. It protects the seed during the growing season. Husk can be used as building material, fertilizer, insulation material and fuel.

Handpicking

How do we separate a stone from rice? If the stones are visible different from the grain, they can be easily picked and separated by hand. This is called handpicking. But if the stones look very similar to the rice grains it is difficult to separate.

Magnetic Separation

In a mixture containing iron, the magnetic property of iron can be used to separate it from non- magnetic substances by using a magnet. Substances that are attracted to a magnet are called magnetic substances. Separating solids using a magnet is called magnetic separation.

Sedimentation

Rice and pulses are often mixed with very fine straw, husk or dust particles which have to be removed before cooking. Are you familiar with the way this is done at home? To remove these particles rice or pulses are washed in water. The lighter impurities float while heavier rice grains sink to the bottom. This is called sedimentation. The water with the impurities is carefully poured down leaving clean rice at the bottom. This is called decantation.

Separating mud from muddy water

Muddy water is a mixture of very fine particles of soil in water. What will happen if muddy water is left undisturbed for some time? Mud being heavy will settle down at the bottom of the beaker and will form the sediment. Water forms the top layer and is called the supernatant liquid. The settling down of heavier components of a mixture when allowed to remain undisturbed for some time is called sedimentation.

Decantation

This process is done after sedimentation. The supernatant liquid is slowly poured out from the container without disturbing the sediment. The part that settles down the bottom of the liquid is called sediment. The water that is obtained after decantation is called the decantate. The process of separating liquid above the sediment is called decantation. But even after decantation the water is not completely free from fine soil particles. How can we remove this? We can do this by filtration. Do you think a strainer or a cloth can filter theses very fine particles? Do it by yourself and find out.

Filtration

We use filter papers to remove the finer impurities. A filter paper has very fine pores much smaller than soil particles. Let us see how to use the filter paper. Take a piece of filter paper. Fold it to make a cone (see figure). Slowly pour the muddy water over the filter paper. On filtration clear water (filtrate) flows down the funnel and mud settles as residue on the filter paper. The method of separating insoluble component (sand, mud etc.) from a mixture using a filter paper is called filtration. The liquid which passes through the filter and comes down is called filtrate and the insoluble component left behind on the filter paper is called residue.

More to know

Combination of methods are used sometimes for complete separation. If the mixture of sand and salt in water has to be separated several methods like sedimentation, decantation, filtration, evaporation and condensation are used.

Activity 7

Group Activity – Students are divided into four groups Each group should suggest a method to separate mixtures and also give reasons why they used a particular method and what property of the components forms the basis for separation. Examples should be drawn from day-to-day life. After the group presents its method to the rest of the class, the whole class will discuss and analyse if the suggested method will work and then make a note of it in the table given below.

Separation Method	Example	Basis For Separation

3.7 Food Adulteration

Sometimes, things that we buy in the market are mixed with harmful and unwanted substances. It is called adulteration. Food can also get adulterated due to carelessness or lack of proper handling. We must be careful about the common adulterants in our consumable goods especially in food. Any adulterated food when consumed will be harmful and can be a health hazard. An adulterated substance will not indicate the true properties of the original substance. For example, used tea leaves are sometimes used as adulterants in tea. Turmeric powder is adulterated with a bright yellow chemical which is poisonous to us.

Do you know?

In most houses people use commercial water filter to remove not only the impurities but also to kill the harmful germs in water using UV rays. Reverse Osmosis (RO) is a process of removing impurities from water to make it potable.

Activity 8

Collect and share information on common adulterants and their detection in food stuff in the class. Watch the youtube video: 10 simple tricks to find adulterated food. https://www.youtube.com/watch?v=XLiWunnudY

Points to Remember

• Matter is anything that has mass and occupies space.
• All matter is made up of extremely small particles called atoms.
• Matter is classified into solids, liquids and gases on the basis of two important factors. a. The way the particles are arranged b. The way the particles attract each other.
• Difference between the properties of solids, liquids and gases is due to the difference in the arrangement of the particles and the nature of the attractive forces between them.
• A pure substance can be an element or a compound and it can be made up of only one kind of particles.
• A mixture is an impure substance containing two or more components physically mixed in any proportion.
• Separation of mixtures is done 1. to remove harmful components. 2. to obtain the useful components. 3. to obtain a substance in a highly pure form
• Different separation methods are adopted depending on the properties of the components.
• Handpicking – Particles reasonably large in size to be recognised can be picked by handpicking.
• Winnowing – Adopted to separate lighter solids from heavier ones.
• Magnetic separation – Separating magnetic substances from non-magnetic substances.
• Sedimentation – Settling down of suspended, insoluble and heavy solid particles (used to separate solid – liquid mixtures).
• Decantation - Process of pouring out the clear supernatant liquid without disturbing the sediment.
• Filtration – Process of separating insoluble solid particles (residue) from a liquid (filtrate) by using a filter paper.
• Adulteration – Making things impure by the addition of a foreign or inferior substance.

EVALUATION

Exercise 1. Choose the correct answer

1. _____ is not made of matter.

a. gold ring b. Iron nail c. Light ray d. Oil drop

2. 200 ml of water is poured into a bowl of 400 ml capacity. The volume of water will be _____

a. 400 ml b. 600 ml c. 200 ml d. 800 ml

3. Seeds from water-melon can be removed by _____

a. hand-picking b. filtration c. magnetic separation d. decantation

4. Lighter impurities like dust when mixed with rice or pulses can be removed by _____

a. filtration b. sedimentation c. decantation d. winnowing

5. _____ is essential to perform winnowing activity.

a. Rain b. Soil c. Water d. Air

6. Filtration method is effective in separating _____ mixture.

a. solid-solid b. solid-liquid c. liquid-liquid d. liquid-gas

7. Among the following _____ is not a mixture.

a. coffee with milk b. lemon juice c. water d. ice cream embedded with nuts Exercise II. Fill in the blanks

1. Matter is made up of

2. In solids, the space between the particles is less than in

3. Grains can be separated from their stalks by

4. Chillies are removed from 'Upma' by method.

5. The method employed to separate clay particles from water is

6. Water obtained from tube wells is usually water.

7. Which among the following will get attracted to by magnet? (safety pins, pencil and rubber band)

Exercise III. State True or False. If false, correct the statement 1. Air is not compressible. 2. Liquids have no fixed volume but have fixed shape. 3. Particles in solids are free to move. 4. When pulses are washed with water before cooking, water is separated from them by filtration. 5. Strainer is a kind of sieve which is used to separate a liquid from solid. 6. Grain and husk can be separated by winnowing. 7. Air is a pure substance. 8. Butter from curd is separated by sedimentation. Exercise IV. Complete the given analogy

1. Solid: Rigidity: Gas: .

2. Large Inter-particle space: Gas: : solid.

3. Solid: Definite shape: : Shape of the vessel.

4. Husk-Grains: Winnowing: Sawdust- Chalk piece:

5. Murukku from hot oil: : Coffee powder residue from decoction:

6. Iron-sulphur mixture: : Mustard seeds from Urad-dhal:

Exercise 5. Match the following

a)

Property	Example
Breaks easily (Brittle)
Bends readily
Can be stretched easily
Gets compressed easily
Gets heated readily

Options: Metal pan, Rubber band, Cotton wool, Mud pot, Plastic wire

b)

A	B	C
1. Separation of visible undesirable components	Water mixed with chalk powder
2. Separation of heavier and lighter components	Sand and water
3. Separation of insoluble impurities	Iron impurities
4. Separation of magnetic components from non-magnetic components	Rice and stone
5. Separation of solids from liquids	Husk and paddy

Options: Magnetic Separation, Decantation, Filtration, Hand-picking, Winnowing

Exercise VI. Answer very briefly

1. Define the term matter.

2. How can husk or fine dust particles be separated from rice before cooking?

3. Why do we separate mixtures?

4. Give an example for mixture and justify your answer with reason.

5. Define - Sedimentation.

6. Give the main difference between a pure substance and an impure substance.

Exercise VII. Answer briefly

1. A rubber ball changes its shape on pressing. Can it be called a solid?

2. Why do gases not have fixed shape?

3. What method will you employ to separate cheese (paneer) from milk? Explain.

4. Look at the picture given below and explain the method of separation illustrated.

5. How can you separate a large quantity of tiny bits of paper mixed with pulses or dal?

6. What is meant by food adulteration?

7. Mr. Raghu returns home on a hot summer day and wants to have buttermilk. Mrs. Raghu has only curd. What can she do to get buttermilk? Explain

Exercise VIII. Higher Order Thinking Questions

1. Distinguish the properties of solid, liquid and gas. Draw a suitable diagram.

2. Using suitable apparatus from your laboratory separate the mixture of chalk powder, mustard oil, water and coins. Draw a flow chart to show the separation process.

3. Justify your answer. Arrangement of particles in three different phases of matter is shown above.

a) Which state is represented by Figure 1?

b) In which state will the inter particle attraction be maximum?

c) Which one of them cannot be contained in an open vessel?

d) Which one can take the shape of its container?

4. Malar's mother was preparing to cook dinner. She accidentally mixed ground nuts with urad-dhal. Suggest a suitable method to separate the two substances so that Malar can have ground nuts to eat.

5. In a glass containing some water, tamarind juice and sugar is added and stirred well. Is this a mixture? Can you tell why? Will this solution be sweet or sour or both sweet and sour?

Exercise IX. Life Skills - Debate

1. Debate on 'Food adulteration and detection'

Exercise 10. Field Trip

1. Visit a nearby paddy field and rice mill and note down the different separating techniques used there. Is technology replacing some traditional practices?

Watch youtube video in the given link https://www.youtube.com/watch?v=9Djc5ZVUyUw https://www.youtube.com/watch?v=DJGRJ4qL4-A

Exercise XI. Sequence Type

1. Write the sequence of steps you would use for making tea. (Use the words: mixture, dissolve, filtrate and residue).

Exercise XII. Topic enrichment – Project

1. Make a fruit or vegetable salad. Give reasons why you think it is a mixture.

2. Connect with sports

Air is not a pure substance. It helps us in many ways from breathing to playing. Balloon sports are a very popular sport. Hot air is lighter than cool air. So, the balloons filled with hot air rise up. Find out more about hot air balloons.

ICT Corner

Types of matter

Step 1: To learn more about the matter around us type Science Kids in the Google browser and select games Go inside and select matter. Now the following logo can you drag will appear on the screen. Then click ok.

Step 2: Three divided columns will appear on the screen. The first section is for solid and the second section is for liquid and the third one is for gas. Now when we press this symbol, at the bottom items will appear at the bottom. We have to drag them to their respective column.

Types of matter URL: http://www.sciencekids.co.nz/gamesactivities/gases.html

Pictures are indicative only

📝 Summary

1. Matter is defined as anything that occupies space and has mass, and is found everywhere around us in the air we breathe, water we drink, and materials we use.
2. Matter is made of atoms, which are the smallest particles of matter that are so small they cannot be seen with eyes or even with a standard microscope.
3. Matter exists in three major states: solid, liquid and gas, which can be differentiated based on the arrangement and spacing of their particles.
4. Particles of matter have space between them and attract each other through forces of attraction, with the spacing and attractive forces varying in different forms of matter.
5. Solids have tightly packed particles with definite shape and volume that do not change when moved from one place to another, and do not need a container to maintain their shape.