Samacheer Kalvi Class 6 Science Solutions Term 1 Chapter 3 Matter Around Us

I. Choose the correct answer:

 

Question 1. .......... is not made of matter
(a) Gold ring
(b) iron nail
(c) light ray
(d) oil drop
Answer: (c) light ray
In simple words: Matter is anything that has mass and takes up space. A light ray is energy and does not have mass or take up space, so it is not matter.

🎯 Exam Tip: Remember that light, sound, and heat are forms of energy, not matter. Anything that can be weighed or measured for volume is matter.

 

Question 2. 200 ml of water is poured into a bowl of 400ml capacity. The volume of water now will be __________
(a) 400 ml
(b) 600 ml
(c) 200 ml
(d) 800 ml
Answer: (c) 200 ml
In simple words: The volume of the water itself does not change just because it is poured into a bigger bowl. It remains 200 ml.

🎯 Exam Tip: The volume of a liquid does not change with the size or shape of its container; only its shape changes to fit the container.

 

Question 3. Seeds from water-melon can be removed by __________ method.
(a) Hand-picking
(b) filtration
(c) magnetic separation
(d) decantation
Answer: (a) Hand-picking
In simple words: Watermelon seeds are big enough to be seen and picked out by hand from the edible fruit part. This is a simple way to separate them.

🎯 Exam Tip: Hand-picking is suitable for separating larger, visible impurities or components from a mixture, especially when they are different in size, shape, or color.

 

Question 4. Lighter impurities like dust, when mixed with rice or pulses, can be removed by __________
(a) filtration
(b) sedimentation
(c) decantation
(d) winnowing
Answer: (d) winnowing
In simple words: Winnowing uses wind or moving air to blow away lighter particles like dust and husk, leaving the heavier rice or pulses behind. It's a traditional method for cleaning grains.

🎯 Exam Tip: Winnowing is effective for separating components with a significant difference in weight when exposed to air current.

 

Question 5. __________ is essential to perform winnowing activity
(a) Rain
(b) Soil
(c) Water
(d) Air
Answer: (d) Air
In simple words: Winnowing needs air, either natural wind or air from a fan, to carry away the lighter husks and dust. Without air, the separation would not happen.

🎯 Exam Tip: The principle of winnowing relies on air currents to separate lighter particles from heavier ones. The air acts as the medium of separation.

 

Question 6. Filtration method is effective in separating __________ mixture.
(a) solid - solid
(b) solid - liquid
(c) liquid - liquid
(d) liquid - gas
Answer: (b) solid - liquid
In simple words: Filtration works by passing a liquid through a filter to catch solid particles that are mixed in it. This method helps clean the liquid or collect the solid.

🎯 Exam Tip: Filtration is a common method used to separate insoluble solid impurities from a liquid, like tea leaves from tea or sand from water.

 

Question 7. From the following __________ is not a mixture
(a) Coffee with milk
(b) lemon juice
(c) Water
(d) ice cream embedded with nuts.
Answer: (c) Water
In simple words: Water is a pure substance made of only H2O molecules, while the other options are mixtures of different things. For example, coffee with milk is a mix of coffee, milk, sugar, and water.

🎯 Exam Tip: A pure substance consists of only one type of particle (atoms or molecules), whereas a mixture contains two or more substances that are not chemically combined.

 

II. State whether the following statements are True or False. If false give the correct statement

 

Question. 1. Air is not compressible.
Answer: False. Air is Compressible.
In simple words: Air can be squeezed into a smaller space. This is why you can pump air into a tire and it gets compressed.

🎯 Exam Tip: Gases like air are highly compressible because their particles are far apart, allowing them to be pushed closer together.

 

Question. 2. Liquids have no fixed volume but have fixed shape.
Answer: False. Liquids have no fixed shape but have fixed volume.
In simple words: Liquids always take the shape of their container, so they don't have a fixed shape. However, their amount (volume) stays the same, no matter what container they are in.

🎯 Exam Tip: Remember that liquids have a definite volume, unlike gases, but their shape is indefinite and adapts to the container.

 

Question. 3. Particles in solids are free to move.
Answer: False. Particles in solids are not free to move.
In simple words: In solids, particles are tightly packed and can only vibrate in their fixed positions, not move freely. This is why solids have a fixed shape.

🎯 Exam Tip: The strong intermolecular forces in solids restrict particle movement, giving solids their rigidity and definite shape.

 

Question. 4. When pulses are washed with water before cooking, the water is separated from them by the process of filtration.
Answer: False. When pulses are washed with water before cooking, the water is separated from them by the process of Decantation.
In simple words: Decantation is simply pouring off the liquid after the solids have settled at the bottom. Filtration would involve a filter paper, which is usually not used when washing pulses.

🎯 Exam Tip: Decantation is used when there's a clear separation between a liquid and settled solid particles, allowing the liquid to be carefully poured away.

 

Question. 5. Strainer is a kind of sieve which is used to separate a liquid from solid.
Answer: False. Strainer is a kind of sieve which is used to separate a solid from liquid.
In simple words: A strainer holds back the solid parts while allowing the liquid to pass through. It helps to separate insoluble solids from liquids, for example, draining pasta.

🎯 Exam Tip: A sieve or strainer always retains the solid particles while letting the liquid pass, effectively separating solid from liquid components of a mixture.

 

Question. 6. Grain and husk can be separated by winnowing.
Answer: True.
In simple words: Winnowing is a common method for separating grains from their lighter husks using wind. The wind blows the husk away, and the heavier grains fall down.

🎯 Exam Tip: This method works because grains are much heavier than husks, making it easy for air currents to lift and remove the lighter material.

 

Question. 7. Air is a pure substance.
Answer: False. Air is a mixture. (Or) Air is not a pure substance.
In simple words: Air is made up of many different gases like nitrogen, oxygen, and carbon dioxide, which are all mixed together but not chemically joined. Pure substances, like water, have only one type of molecule.

🎯 Exam Tip: Remember that mixtures can be separated by physical means, while pure substances cannot. Air can be separated into its constituent gases.

 

Question. 8. Butter from curds is separated by sedimentation.
Answer: False. Butter from curds is separated by churning.
In simple words: Churning involves rapidly mixing or shaking the curds, which causes the butterfat to clump together and separate from the liquid. Sedimentation is when heavier particles settle at the bottom.

🎯 Exam Tip: Churning is a mechanical process that applies force to separate components, especially useful for separating fats like butter from dairy products.

 

III. Match the following

 

Question 1. Match the following based on property and example.

Answer:
1. - d
2. - e
3. - b
4. - c
5. - a
In simple words: This match-up helps us understand how different materials behave based on their properties. For example, mud pots break easily, and metal pans get hot fast.

🎯 Exam Tip: When matching, look for a clear, defining property for each item. Start with the easiest ones to link, then use elimination for the rest.

 

Question 2. Match the following based on separation methods.

Answer:In simple words: This table explains various methods to separate mixtures. For example, you can hand-pick big visible pieces, use wind for lighter husks, or magnets for iron.

🎯 Exam Tip: Understand the properties of the substances in a mixture (like size, weight, magnetism) to choose the correct separation method.

 

IV. Fill in the blanks

 

Question. 1. Matter is made up of __________.
Answer: Atoms
In simple words: Everything around us, and even inside us, is built from tiny, tiny particles called atoms. They are the basic building blocks of all matter.

🎯 Exam Tip: Remember that atoms are the fundamental units of matter, and they combine to form molecules and larger structures.

 

Question. 2. In solids, the space between the particles is less than in __________.
Answer: Liquids
In simple words: Solids have very little space between their particles, making them tightly packed. Liquids have more space than solids but less than gases, allowing their particles to move around.

🎯 Exam Tip: The amount of space between particles directly influences the state of matter, affecting properties like compressibility and fluidity.

 

Question. 3. Grains can be separated from their stalks by __________.
Answer: Threshing
In simple words: Threshing is the process of beating or hitting harvested plants to remove the grains from their stalks. This step comes before winnowing.

🎯 Exam Tip: Threshing is a mechanical separation process used in agriculture to liberate grains from the inedible parts of the plant.

 

Question. 4. Chillies are removed from 'upma' by __________ method.
Answer: Hand picking
In simple words: Chillies are big enough to be easily seen and picked out of 'upma' using your hands. This is a simple and effective way to remove them.

🎯 Exam Tip: Hand-picking is suitable for separating larger, clearly visible components from a mixture, especially when they are distinctly different in size or shape.

 

Question. 5. The method employed to separate clay particles from water is __________.
Answer: Filtration
In simple words: Clay particles are very fine and remain suspended in water, making it cloudy. Filtration uses a filter material to catch these tiny solid particles, letting clean water pass through.

🎯 Exam Tip: Filtration is ideal for separating very small insoluble solid particles suspended in a liquid, as the filter paper allows only the liquid to pass.

 

Question. 6. Among the following items: Safety pins, pencil and rubber band, __________ will get attracted to a magnet.
Answer: Safety pins
In simple words: Safety pins are usually made of steel, which is a magnetic material. Pencils and rubber bands are not magnetic and will not be attracted.

🎯 Exam Tip: Only ferromagnetic materials like iron, nickel, cobalt, and their alloys are attracted to magnets; materials like wood, rubber, or plastic are not.

 

Question. 7. Water obtained from tube wells is usually __________ water.
Answer: Impure
In simple words: Tube well water comes from underground and often contains dissolved minerals, salts, and sometimes even microorganisms. Therefore, it is usually not pure water.

🎯 Exam Tip: Groundwater from wells or tube wells can contain various dissolved substances from the soil and rocks, making it impure and often requiring treatment for drinking.

 

V. Complete the given analogy

 

Question. 1. Solid: rigidity :: gas: __________.
Answer: Compressibility
In simple words: Just as solids are known for being rigid and hard to bend, gases are known for how easily they can be squeezed into a smaller space.

🎯 Exam Tip: Rigidity is a key property of solids, while compressibility is a defining characteristic of gases, reflecting the spacing and movement of their particles.

 

Question. 2. Large Inter-particle space: gas:: __________ : solid.
Answer: Little inter-particle space
In simple words: Gases have a lot of empty space between their particles. In contrast, solids have very little space, meaning their particles are tightly packed together.

🎯 Exam Tip: The spacing between particles is a fundamental difference between states of matter, with gases having the most space and solids the least.

 

Question. 3. Solid : definite shape :: __________ : shape of the vessel.
Answer: Liquids
In simple words: Solids keep their own shape no matter where you put them. Liquids, however, always take on the shape of the container they are in.

🎯 Exam Tip: This analogy highlights the difference in particle arrangement and intermolecular forces, which determine whether a substance has a definite shape or not.

 

Question. 4. Husk-grains: winnowing:: Sawdust-chalk piece: __________.
Answer: Sedimentation and Decantation
In simple words: Winnowing separates lighter husk from heavier grains. Similarly, for sawdust and chalk, if mixed with water, the heavier chalk will settle, and you can pour off the sawdust.

🎯 Exam Tip: This analogy connects separation methods to the physical properties (like weight and density) of the components being separated.

 

Question. 5. Murukku from hot oil: __________ :: coffee powder residue from decoction.
Answer: Hand picking; Filtration.
In simple words: Murukku can be lifted out of hot oil by hand or with tongs because it's large. Coffee powder residue is separated from liquid coffee by pouring it through a filter.

🎯 Exam Tip: Choose separation methods based on the size, state, and properties of the components. Hand-picking for large solids, filtration for fine insoluble solids.

 

Question. 6. Iron-sulphur mixture: __________ :: Mustard seeds from Urad-dhal: Rolling.
Answer: Magnetic Separation.
In simple words: An iron-sulphur mixture can be separated using a magnet because iron is magnetic. For mustard seeds and urad-dhal, if they are different in shape or size, you might use rolling or sieving to separate them.

🎯 Exam Tip: Magnetic separation is highly effective when one component of a mixture is magnetic and the other is not.

 

VI. Very short answer

 

Question 1. Define the term matter.
Answer: Matter is defined as anything that has mass and takes up space. It exists in different forms, such as solid, liquid, and gas. For example, a chair, water, and air are all forms of matter.
In simple words: Matter is anything that has weight and takes up room. You can find it as solids, liquids, or gases.

🎯 Exam Tip: The two key characteristics of matter are having mass and occupying space (volume). Keep these definitions clear for full marks.

 

Question 2. How can husk or fine dust particles be separated from rice before cooking?
Answer: Before cooking, husk or fine dust particles can be separated from rice primarily by 'Winnowing' or 'Hand-picking'. Winnowing uses wind to blow away the lighter impurities, while hand-picking removes larger, visible unwanted items. Both methods ensure the rice is clean for cooking.
In simple words: You can clean rice by blowing away the light husks with wind (winnowing) or by picking out any bigger bits by hand.

🎯 Exam Tip: Mentioning both winnowing for lighter particles and hand-picking for larger impurities shows a complete understanding of separation techniques for grains.

 

Question 3. Why do we separate mixtures?
Answer: We separate mixtures for several reasons: to remove harmful or unwanted substances, to obtain useful components, or to purify a substance for a specific use. For instance, separating stones from rice makes it safe to eat, and separating cream from milk gives butter.
In simple words: We separate mixtures to get rid of bad things, to find useful things, or to make something pure for its purpose.

🎯 Exam Tip: Focus on the practical applications of separation: removal of impurities, extraction of valuable components, and purification.

 

Question 4. Give an example for mixture and justify your answer with reason.
Answer: An example of a mixture is 22 Carat Gold. This is composed of Gold and Copper (or) Gold and Cadmium. It is a mixture because the gold and copper are simply mixed together, not chemically combined. This mixing changes the properties of pure gold, making it harder and more durable, which is useful for making jewelry.
In simple words: 22 Carat Gold is a mixture of gold and copper. They are just blended, not chemically stuck together, which makes the gold stronger for jewelry.

🎯 Exam Tip: When justifying an example of a mixture, explain that the components retain their individual properties and are not chemically bonded.

 

Question 5. Define Sedimentation.
Answer: Sedimentation is the process where heavy solid particles in a mixture of liquid and an insoluble solid settle down at the bottom due to gravity. This happens when the mixture is left undisturbed for some time. An example is sand settling at the bottom of a glass of water.
In simple words: Sedimentation is when heavy bits in a liquid drop to the bottom if left still.

🎯 Exam Tip: The key factors for sedimentation are gravity and a sufficient difference in density between the solid particles and the liquid.

 

Question 6. Give the main difference between a pure substance and an impure substance.
Answer:Pure Substance: A pure substance is made up of only one kind of particles. It cannot be separated into simpler substances by physical means. For example, distilled water is a pure substance. Impure Substance: An impure substance (or mixture) has particles of other substances mixed in it. It can be separated into its components by physical means. For example, salt water is an impure substance.
In simple words: Pure substances have only one type of particle and can't be easily split. Impure substances are mixes of different particles and can be separated easily.

🎯 Exam Tip: The key distinction lies in the type of particles and the methods of separation: pure substances have uniform composition and require chemical methods, while mixtures have varied composition and use physical methods.

 

VII. Short Answer.

 

Question 1. A rubber ball changes its shape on pressing. Can it be called a solid?
Answer: Yes, a rubber ball can still be called a solid. Solids have a definite shape and size. The rubber ball changes its shape only when we apply an external force by squeezing it. Once the force is removed, it returns to its original shape, which is a property of elastic solids.
In simple words: Yes, a rubber ball is a solid. It only changes shape when you press it, but it goes back to its normal shape when you let go.

🎯 Exam Tip: Remember that some solids are elastic and can change shape under force but return to their original form, maintaining their solid state.

 

Question 2. Why do gases not have fixed shape?
Answer: Gases do not have a fixed shape because the forces of attraction between their particles are very weak. This allows the gaseous particles to move freely and far apart from each other. As a result, gases spread out and take the full shape of any container they are put into.
In simple words: Gas particles are very loose and move all over the place because they don't stick together strongly. So, gas fills up any container it is in.

🎯 Exam Tip: The key reason for gases lacking a fixed shape is the weak intermolecular forces and the high kinetic energy of their particles, leading to free movement.

 

Question 3. What method will you employ to separate cheese (paneer) from milk? Explain.
Answer: To separate cheese (paneer) from milk, the method commonly employed is 'Churning followed by Coagulation'. First, milk is curdled (coagulated) by adding an acidic substance like lemon juice, causing the milk proteins to clump together and form curds (paneer). Then, the mixture is churned or stirred, separating the solid paneer from the liquid whey. Finally, the paneer is collected, often by straining. Here are the important steps in making cheese from milk:
1. Acidification
2. Coagulation
3. Separating curds and whey
4. Salting
5. Shaping
6. Ripening
In simple words: First, you make the milk curdle by adding something sour like lemon. Then, you stir or churn it, and the solid cheese (paneer) separates from the watery part. You then strain the cheese out.

🎯 Exam Tip: Understand that cheese making involves both chemical change (coagulation) and physical separation techniques (churning, straining) to isolate the solid protein from the liquid components.

 

Question 4. Look at the picture given below and explain the method of separation illustrated.
[Image of sieving process]
Answer: The picture illustrates the 'Sieving' method of separation. This method is used to separate solid particles of different sizes. When a mixture is passed through a sieve, smaller particles pass through the holes, while larger particles are retained on the sieve. For example, this method is used to separate bran from flour or sand from gravel.
In simple words: The picture shows sieving. This is a way to separate small bits from big bits using a net with holes. Small things go through, and big things stay.

🎯 Exam Tip: Sieving is effective for separating solid mixtures where components have distinct particle sizes. Always remember to mention the size difference.

 

Question 5. How can you separate a mixture of a large number of tiny bits of paper mixed with pulses/dal?
Answer: We can separate a mixture of tiny bits of paper and pulses/dal by "Winnowing". Since paper bits are much lighter than pulses/dal, when the mixture is dropped from a height in the presence of wind or air from a fan, the lighter paper bits will be carried away by the air, while the heavier pulses/dal will fall closer and form a separate heap. This method effectively cleans the pulses.
In simple words: You can use winnowing to separate paper bits from pulses. The wind will blow away the light paper, and the heavier pulses will fall straight down.

🎯 Exam Tip: The key principle here is the difference in weight between the components. Winnowing utilizes air currents to separate lighter particles from heavier ones.

 

Question 6. What is meant by food adulteration?
Answer: Food adulteration is the process of mixing harmful and unwanted substances with foodstuffs that are bought in the market. This practice is illegal and makes the food unsafe or of lower quality, often done to increase quantity or reduce cost. For example, adding pebbles to rice is a form of adulteration.
In simple words: Food adulteration means adding bad or useless things to food we buy. It makes the food worse or even harmful.

🎯 Exam Tip: Focus on the intent (mixing harmful/unwanted substances) and the consequence (making food unsafe/lower quality) when defining food adulteration.

 

Question 7. Mr. Raghu returns home on a hot summer day and wants to have buttermilk. Mrs. Raghu has only curds. What can she do to get buttermilk? Explain.
Answer: To make buttermilk from curds, Mrs. Raghu should take half a cup of curd and add half a cup of water to it. Then, she should mix it very well, ideally by churning or whisking. This process will create a refreshing buttermilk drink. This mixing breaks down the curds and dilutes them, giving the desired consistency and taste.
In simple words: Mrs. Raghu needs to take half a cup of curd, add half a cup of water, and mix it really well. This will turn it into buttermilk.

🎯 Exam Tip: This is a simple dilution and mixing process. The key is to add water to the curd and blend them thoroughly.

 

VIII. Answer In Detail.

 

Question 1. Distinguish between properties of solid, liquid, gas. Draw a suitable diagram.
Answer: The main differences in properties between solids, liquids, and gases are:

(Note: The diagram showing particle arrangements for solids, liquids, and gases is not included as per content processing rules.)
In simple words: Solids keep their shape and size, are hard to squeeze, and their tiny parts are tightly packed. Liquids take the shape of their container, are slightly squishy, and their parts move freely. Gases have no fixed shape or size, are easy to squeeze, and their parts fly around everywhere.

🎯 Exam Tip: When distinguishing between states of matter, always focus on shape, volume, compressibility, intermolecular forces, and particle movement as key differentiating properties.

 

Question 2. Using a 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.
Answer: To separate a mixture of chalk powder, mustard oil, water, and coins, we can follow these steps:
1. **Magnetic Separation (for Coins):** First, use a magnet to attract and remove the coins, as they are metallic and magnetic. This will separate the coins from the rest of the mixture.
2. **Sedimentation and Decantation (for Chalk Powder and Water):** Next, allow the remaining mixture of chalk powder, mustard oil, and water to stand undisturbed. The heavier chalk powder will settle at the bottom (sedimentation). After it settles, carefully pour off the mustard oil and water mixture from the settled chalk powder (decantation).
3. **Separating Funnel (for Mustard Oil and Water):** Transfer the mixture of mustard oil and water into a separating funnel. Since oil and water do not mix and have different densities, they will form two separate layers. Mustard oil, being lighter, will form the upper layer, and water will form the lower layer. Open the tap of the separating funnel to drain the lower water layer first, then collect the mustard oil from the upper layer separately.
(Note: A flowchart depicting these steps would visually represent the sequence of separations.)
In simple words: First, use a magnet to take out the coins. Then, let the chalk settle at the bottom and pour out the oil and water. Finally, use a special funnel to separate the oil from the water, as they form layers.

🎯 Exam Tip: When separating multiple components, identify the distinct properties of each (magnetic, density, solubility) and apply methods in a logical sequence from easiest to most complex.

 

HOTS

 

Question 1. 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.
Answer: The groundnuts can be separated from urad-dhal by the 'Hand-picking' method. This is because groundnuts and urad-dhal usually differ in size, shape, and color, making them easily distinguishable to the eye. Malar's mother can simply pick out the groundnuts by hand from the mixture.
In simple words: Malar's mother can separate the groundnuts from urad-dhal by hand-picking because they look different in size and color.

🎯 Exam Tip: Hand-picking is the simplest and most effective method for separating visually distinct solid components from a mixture, especially when the quantities are manageable.

 

Question 2. 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?
Answer:
1. Yes, the contents in the glass form a mixture.
2. This is because it is made up of two or more ingredients (water, tamarind juice, and sugar) that are physically combined and can be separated. They retain their individual properties when mixed.
3. This mixture will be both sweet and sour. Tamarind juice is naturally sour, and sugar is sweet. When mixed, both tastes will be present in the solution.
In simple words: Yes, it's a mixture because water, tamarind, and sugar are just mixed together, not chemically changed. The drink will taste both sweet from the sugar and sour from the tamarind.

🎯 Exam Tip: Remember that in a mixture, the original properties of the components are retained. So, if you mix something sweet and something sour, the mixture will taste both sweet and sour.

 

Question 3. Justify your answer. An arrangement of particles in three different phases of matter is shown above.
[Image of particles in FIG 1 (gas), FIG 2 (liquid), FIG 3 (solid)]
(a) Which state is represented by fig. 1?
Answer: Figure 1 represents a gas.
In simple words: The particles in Figure 1 are spread far apart and move randomly, which is how gas particles behave.

🎯 Exam Tip: In diagrams of states of matter, look for the spacing and arrangement of particles. Widely spaced and random particles indicate a gas.

 

(b) In which will be the interparticle attraction maximum?
Answer: Inter particle attraction is maximum in solids (fig. 3)
In simple words: In Figure 3, the particles are very close and orderly, showing strong attraction, which is typical for solids.

🎯 Exam Tip: Strong interparticle attraction means particles are held tightly together, resulting in a definite shape and volume, characteristic of solids.

 

(c) Which one of them cannot be contained in an open vessel?
Answer: A gas (fig. 1) cannot be contained in an open vessel.
In simple words: Gas particles move freely and fill any space, so they would escape from an open container.

🎯 Exam Tip: Gases have no definite volume and spread out to fill their container, which means they cannot be kept in an open vessel.

 

(d) Which one can take the shape of its container?
Answer: Liquid (fig.2) can take the shape of its container.
In simple words: The particles in Figure 2 can move around each other, allowing the liquid to flow and fit the shape of its container.

🎯 Exam Tip: Liquids have indefinite shapes because their particles can slide past one another, enabling them to conform to the shape of any container they are in.

 

Samacheer Kalvi 6th Science Matter Around Us Additional Important Questions and Answers

 

I. Choose The Correct Answer

 

Question 1. Which of the following are homogeneous in nature?
(i) ice
(ii) wood
(iii) soil
(iv) Air
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (iii) and (iv)
Answer: (c) (i) and (iv)
In simple words: Ice is pure water in solid form, and air is a uniform mixture of gases. Both have the same composition throughout.

🎯 Exam Tip: Homogeneous means uniform in composition and properties throughout. Ice is pure H2O, and air is a uniform mixture of gases.

 

Question 2. A standard sheet of paper is about __________ atoms thick.
(a) Thousands
(b) Crores
(c) Lakhs
(d) Million
Answer: (c) Lakhs
In simple words: Even though a sheet of paper feels thin, it is actually many hundreds of thousands of atoms thick, showing how incredibly small atoms are.

🎯 Exam Tip: This question highlights the incredibly small scale of atoms and how many are needed to form even a seemingly thin object.

 

Question 3. Which among the following is not a matter?
(a) Electron
(b) Blood
(c) Moonrock
(d) Humidity
Answer: (a) Electron
In simple words: Matter is anything that has mass and takes up space. An electron has mass, but it is a fundamental particle, not a substance in the common sense of matter.

🎯 Exam Tip: Remember that matter is typically defined as having both mass and volume. While electrons have mass, their nature is subatomic and different from everyday matter like blood or moonrock.

 

Question 4. One dot that you make with your pen has more than lakh molecules.
(a) One
(b) Two
(c) Four
(d) Three
Answer: (b) Two
In simple words: Even a tiny dot made by a pen contains an incredibly large number of molecules, more than two lakh (200,000) of them. This shows how tiny molecules are.

🎯 Exam Tip: Questions about the number of particles emphasize the extremely small size of atoms and molecules. Always think about how many tiny units make up even a small visible object.

 

Question 5. Pure rava, when adulterated with wheat flour, is separated by
(a) Sieving
(b) Filtration
(c) Winnowing
(d) Threshing
Answer: (a) Sieving
In simple words: Sieving is the best way to separate rava and wheat flour because they have different particle sizes. The smaller flour particles pass through the sieve, while the larger rava particles stay behind.

🎯 Exam Tip: Sieving is a common method for separating solid mixtures where the components have noticeable differences in their particle sizes. It's often used in kitchens and construction sites.

II. Match the following

 

Question 1. Match the following.
Answer:

In simple words: This table matches different mixtures with the best ways to separate them. For example, you evaporate salt from water, filter tea leaves, use a magnet for iron, and churn butter from curds.

🎯 Exam Tip: When matching, look for key properties of the substances involved. For instance, if one component is magnetic, magnetic separation is the obvious choice. If one evaporates, that's key.

III. Fill in the blanks

 

Question 1. .......... particles are tightly packed into a definite shape.
Answer: Solid
In simple words: In a solid, the particles are very close together and hold a fixed position, which gives solids their definite shape.

🎯 Exam Tip: Remember the arrangement of particles in different states of matter: tightly packed in solids, close but mobile in liquids, and far apart in gases.

 

Question 2. The tendency of particles to spread out in order to occupy the available space is ..........
Answer: diffusion
In simple words: Diffusion is when particles naturally spread out from a crowded area to a less crowded area until they are evenly mixed throughout the space.

🎯 Exam Tip: Diffusion is a spontaneous process where particles move from a region of higher concentration to a region of lower concentration, often observable with gases and liquids.

 

Question 3. The purest form of gold is denoted by ..........
Answer: 24 carat
In simple words: Gold is measured in carats, and 24 carat gold means it is 100% pure gold with no other metals mixed in.

🎯 Exam Tip: Understanding carats is important for jewelry. 24 carat is pure gold, while lower carat values like 22K or 18K mean other metals are mixed in for strength or color.

 

Question 4. Milk is a ..........
Answer: mixture
In simple words: Milk is not a single pure substance; it is a mixture of water, fats, proteins, and other small particles.

🎯 Exam Tip: Classifying common substances as pure substances or mixtures is a fundamental concept. Pure substances have only one type of particle, while mixtures have two or more.

 

Question 5. The principle of .......... is used in washing machines.
Answer: centrifugation
In simple words: Washing machines use centrifugation to spin clothes very fast, pushing the water out of the fabric due to a strong outward force.

🎯 Exam Tip: Centrifugation is a separation method that uses rapid spinning to separate components of a mixture based on their density. Heavier particles move further from the center.

IV. Very short answer.

 

Question 1. Name the two microscopes which are used to identify the structure of the atom.
Answer:
1. SEM – Scanning Electron Microscope
2. TEM – Tunnelling Electron Microscope
In simple words: To see the tiny parts of an atom, scientists use special powerful microscopes called Scanning Electron Microscopes (SEM) and Tunnelling Electron Microscopes (TEM).

🎯 Exam Tip: Electron microscopes like SEM and TEM use beams of electrons instead of light to create images of very small objects, allowing us to see atomic structures.

 

Question 2. What type of matter glass is?
Answer: Glass appears to be a solid, but it is actually a very slow-moving liquid. This unique property makes it behave differently over long periods.
In simple words: Glass looks like a solid, but it's really a very thick, slow-moving liquid. Over many years, it can flow a tiny bit.

🎯 Exam Tip: Glass is often called an "amorphous solid" or a "supercooled liquid." This means its particles are arranged randomly like a liquid, but it has the rigidity of a solid at room temperature.

 

Question 3. Give two examples of diffusion.
Answer:
1. The spread of a drop of ink in a glass of water.
2. The spread of the smell from an incense stick.
In simple words: Diffusion happens when things mix by themselves, like when ink spreads in water or the smell of incense fills a room.

🎯 Exam Tip: Remember that diffusion is faster in gases than in liquids because gas particles move more freely and are farther apart.

 

Question 4. Mention the method of separation of Bran from flour. Explain.
Answer: Bran is separated from flour using 'sieving'. This method works because solid particles of different sizes can be easily separated by shaking them through a sieve.
In simple words: We separate bran from flour by sieving, which means shaking it through a mesh. The fine flour goes through, and the larger bran bits stay on top.

🎯 Exam Tip: Sieving is effective for separating solid mixtures where the components have different particle sizes, allowing smaller particles to pass through the mesh while larger ones are retained.

 

Question 5. Define the term 'Liquefaction of gases'.
Answer: Liquefaction of gases is the process where substances in their gaseous state are converted into a liquid state. This usually happens by cooling the gas or increasing its pressure.
In simple words: Liquefaction of gases means turning a gas into a liquid, like turning steam into water.

🎯 Exam Tip: Gases can be liquefied by either decreasing their temperature (cooling them down) or increasing the pressure on them, or both, which brings their particles closer together.

V. Answer in detail

 

Question 1. What are the similarities between a gas and a liquid?
Answer:
1. Neither a gas nor a liquid has a definite shape; they both take the shape of their container.
2. The particles of gases and liquids can move freely past each other, a movement known as diffusion. This allows them to mix easily.
3. Liquids can evaporate into gases, and gases can condense back into liquids, showing a reversible change of state.
4. Both gases and liquids have some degree of compressibility, meaning their volume can be slightly reduced by applying pressure, though gases are far more compressible.
In simple words: Both gases and liquids do not have their own shape, they flow and fill containers, their particles can move around, and they can change into each other (gas to liquid, liquid to gas).

🎯 Exam Tip: Focus on the lack of fixed shape and the mobility of particles when comparing liquids and gases. These are key characteristics that distinguish them from solids.

 

Question 2. How do decantation and filtration differ and which is faster?
Answer: Decantation involves carefully pouring out the liquid from a mixture after the solid particles have settled at the bottom. Filtration, on the other hand, involves passing the mixture through a filter medium (like filter paper) that traps the solid particles while allowing the liquid to pass through. Decantation is generally faster if the solid settles quickly, but it may not separate all the fine particles. Filtration can be slower, especially for very fine particles, but it usually provides a more complete and cleaner separation of solids from liquids. Normally, filtration gives a better separation than decantation, resulting in a purer liquid.
In simple words: Decantation is just pouring off the clear liquid after solids sink, which is fast but might leave some bits. Filtration uses a filter to catch all the solids, making the liquid very clean, but it can take more time.

🎯 Exam Tip: When choosing between decantation and filtration, consider the size of the solid particles and the desired purity of the liquid. Decantation is for larger, fast-settling particles, while filtration is for finer separation.