JK Academy Maharashtra Board Class 6 Science Solutions Chapter 5 Substances in the Surroundings – Their States and Properties
Balbharti Maharashtra State Board Class 6 Science Solutions Chapter 5 Substances in the Surroundings – Their States and Properties Notes, Textbook Exercise Important Questions and Answers.
Maharashtra State Board Class 6 Science Solutions Chapter 5 Substances in the Surroundings – Their States and Properties
Class 6 Science Chapter 5 Substances in the Surroundings – Their States and Properties Textbook Questions and Answers
Exercise
1. In the paragraph below, write ‘solid’, ‘liquid’ or ‘gas’ in each of the brackets depending on the substance referred to just before.
On a bright sunny day, Riya and Gargi are playing with a ball ( ……..) in the park. Gargi feels thirsty. So, Riya brings tender coconut water ( ……..) for her. At the same time, a strong breeze (……….) starts blowing and it also begins to rain (……… ). They run back into the house (……. ), change their clothes ( ……) and then their mother gives them a cup (…….) of hot milk (……) to drink.
Answer:
On a bright sunny day, Riya and Gargi are playing with a ball (solid) in the park. Gargi feels thirsty. So, Riya brings tender coconut water (liquid) for her. At the same time, a strong breeze (gas) starts blowing and it also begins to rain (liquid). They run back into the house (solid), change their clothes (solid) and then their mother gives them a cup (solid) of hot milk (liquid) to drink.
2. Discuss.
(a) Riya pours some water from her bottle into another bottle. Does it change the shape of the water?
Answer: Yes, the shape of water changes and takes the shape of the new bottle, as water is in liquid state. Liquids do not have a shape of its own. They take the shape of the container.
(b) Halima picks up a small stone from the ground and puts it in the water in a dish. Does the shape of the stone change?
Answer: No, the shape of the stone does not change. As the stone is in a solid state, it retains its shape.
3. Write the properties of these substances.
Water, glass, chalk, iron ball, sugar, salt, flour, coal, soil, pen, ink, soap.
Answer:
| Substance | State | Properties |
| 1. Water | Liquid | Fluidity, density, solubility, transparency, thermal conductivity. |
| 2. Glass | Solid | Brittleness, hardness, density, transparency. |
| 3. Chalk | Solid | Brittleness, density. |
| 4. Iron ball | Solid | Hardness, density, malleability, ductility, electrical ductility, conductivity, thermal conductivity, luster, sonority. |
| 5. Sugar | Solid | Brittleness, density, solubility. |
| 6. Salt | Solid | Brittleness, density, solubility. |
| 7. Flour | Solid | Density, solubility. |
| 8. Coal | Solid | Brittleness, density, thermal conductivity. |
| 9. Soil | Solid | Brittleness, density. |
| 10. Pen | Solid | Hardness, density. |
| 11. Ink | Liquid | Fluidity, density, solubility. |
| 12. Soap | Solid | Brittleness, hardness, density, solubility. |
4. What is sublimation? Write the names of everyday substances that sublimate.
Answer: The change of a solid substance directly into a gas or vapour without first changing into a liquid is called sublimation.
Substances that sublimate are: iodine, naphthalene balls, camphor, etc.
5. What is it made from? Why?
(a) A sickle to cut sugarcane.
Answer: A sickle is made of iron because iron is hard and malleable. Iron can be given a desired shape and sharpened to make the edges very thin. This helps in holding and cutting anything easily.
(b) The sheets used for roofing.
Answer: The sheets of roofing are made of aluminum or plastic.
Aluminum is hard, light weight, malleable and durable. Plastic is hard, light weight, transparent, can be made into any shape and is durable.
(c) A screwdriver
Answer: A screwdriver is made of steel. A screwdriver is used to push or remove screws, so it has to be very hard and strong. Steel is very strong and hard as it is made of a mixture of different metals.
(d) A pair of tongs.
Answer: A pair of tongs are used in the kitchen, so it has to be strong, hard, rust free and durable. So it is made up of steel.
(e) Electric cables.
Answer: Electric cables are made of metals and covered with plastic. Electric cables are used to supply electricity. As metals are good conductors of electricity, ductile and durable, they are used as electric wires. If electric wires are left open, people made get shock from electric current so the wires are covered with plastic as plastic is bad conductor of electricity.
(f) Ornaments.
Answers: Ornaments are made of metals. Metals are malleable and ductile i.e. they can be drawn into sheets or wires.
(g) Pots and pans.
Ans. Pots and pans are made of mud, clay or metals. Pots and pans are used for cooking and as mud, clay and metals are good conductors of heat, they are used to make pots and pans.
6 What will happen if….? And why ?
(a) Nails are made of plastic.
Answer: Nails are used for fix things and hold things together. If nails are made of plastic, they will break while hammering.
(b) A bell is made of wood.
Ans. A bell is used to produce sound. Wood does not have the property of sonority. Therefore if a bell is made of wood it will not produce a sound.
(c) Rubber is not fitted on a pair of tongs.
Ans. Tongs are made of metal which is good conductor of heat. Rubber is a bad conductor of heat. If rubber is not fitted on a pair of tongs, then they will get heated up when they are held near the fire.
(d) A knife is made of wood.
Answer: A knife is used to cut things. It is made of metal as metal is malleable. So its edges can be sharpened. Wood is not malleable. So a knife made of wood cannot be sharpened and therefore will not be able to cut things easily.
(e) An axe is made of rubber.
Answer: An axe is used to chop wood. It has to be hard, so it is made of iron or steel. Rubber on the other hand is not hard. An axe made of rubber will not be able to chop wood.
7. Who am I?
(a) I’m found in a thermometer, I measure your temperature.
Answer: Mercury
(b) I make things hot or cold.
Answer: Temperature
(c) I have no shape whatsoever!
Answer: Liquid, Gas
(d) I dissolve in water, but not in kerosene.
Answer: Soluble substances
8. Why does this happen?
(a) Coconut oil thickens in winter.
Answer:
During winter the temperature falls. Coconut oil which is in liquid state loses heat, due to the fall in temperature and changes to solid state.
(b) Kerosene left open in a dish disappears.
Answer: Kerosene when left in the open, gains heat and so changes from liquid state to gaseous state. Therefore it disappears.
(c) The fragrance of incense sticks lighted in one corner of a room spreads to the other corner.
Answer: When incense stick is lighted, it burns and releases smoke. The smoke contains the fragrance. As smoke is in the gaseous sate it spread throughout the room, from one corner to the other.
(d) What you see in the picture. (for the picture refer the text book on page 41)
Answer: In the picture we see that the ball floats whereas the apple sinks in the water. This is because the apple has greater density, so it sinks. On the other hand the ball has less density so it floats.
Activity :
Find out how the big statues of wax are made.
Visit a jeweler’s shop and find out how ornaments are made.
Extra Textual Questions:
Can you recall?
Name the solid, liquid and gaseous states of water.
Answer: The solid, liquid and gaseous state of matter are ice, water and water vapour.
Let’s try this.
Take pieces of wax in a bowl and heat them on a candle or spirit lamp.
1. How do the pieces of wax change?
Answer: The solid pieces of wax change to liquid state.
2. What was the initial state of wax?
Answer: The initial state of wax was solid state.
3. What did it get converted into?
Answer: The solid pieces of wax change to liquid state.
Now keep the same bowl in cold water. What happens?
Answer: The liquid wax changes to solid state.
Can you tell?
Read this list of substances : Spirit, camphor, petrol, ghee, coconut oil, naphthalene balls, ammonium chloride (navsagar).
1. Which ones freeze in winter?
Answer: ghee and coconut oil freezes in winter.
2. Which liquid have you seen change into a vapour?
Answer: Spirit and petrol change into vapour.
3. Which solids directly change into the gaseous state?
Answer: camphor, naphthalene balls and ammonium chloride (navsagar) change to its gaseous state.
What do we learn from this?
Answer: The state of a substance changes if it is heated or cooled. Every substance in our surroundings, is found in either the solid, liquid, or gaseous state.
Can you tell?
Does water change into vapour the moment we place the vessel on a stove?
Answer: No.
Does water kept in fridge change at once into ice?
Answer: No.
How do we tell how hot or cold a substance is?
Answer: We can tell how hot or cold a substance is by touching it or measuring its temperature with a thremometre.
Let’s try this.
Take some sand in a crucible. Put a few iodine crystals on it. Place the crucible on a tripod to heat it. Block the stem of the funnel with a cotton plug and place it inverted over the crucible. Light the burner and heat the mixture in the crucible. Observe the changes.
Why does this happen?
Answer: Iodine crystals do not melt on heating but change directly to the gaseous state. When the fumes of iodine hit the walls of the funnel they cool to form solid crystals of iodine and stick to the funnel walls. Thus, on heating, iodine does not melt and change to a liquid but directly changes to the gaseous state. The change of a solid substance directly into a gas or vapour without first changing into a liquid is called sublimation.
Use your brain power!
On opening a box of camphor, its smell spreads all around.
Why does this happen?
Answer: Camphor is a sublimate substance. Sublimate substances directly change from the solid to gas or vapour on absorbing heat. Thus as soon as the box of camphor is opened, camphor changes to vapour and spreads in the room.
What will happen if pressure is applied on substances like chalk, brick, alum, glass or a rajgira wadi ?
Answer: These substances break into small pieces or particles. Such substances are said to be brittle. This property of substances is called brittleness.
Take an iron nail. Try to pierce a cardboard sheet, wet mud and a piece of wood using the nail. What happens? The nail easily pierces wet mud, but not the piece of wood. It can pierce the cardboard sheet with some effort. Why does this happen?
Answer: The hardness of a substance is determined by how much resistance it offers to the substances being pushed through it.
Which is the hardest known substance?
Answer: Diamond is the hardest known material.
Stretch a rubber band and let it go or apply pressure on a piece of sponge and release it. What do you see?
Answer: The rubber band and the sponge go back to their original shape. Some substances change their shape when a force is applied on them but return to their original shape and size when the force is removed. This property is called elasticity.
If two blocks of the same size, one wooden and the other of iron, are weighed in a balance, how would they compare?
Answer: The mass of different substances having the same volume can be different. This difference is because of the difference in their densities.
Take a glass of water. Add some salt, fine sand and sugar to it and try to dissolve them. Repeat this, replacing water with kerosene. What do you observe?
Answer: Some solid substances dissolve in a particular liquid. If a solid does not dissolve in a liquid, it is said to be insoluble in that liquid e.g. salt is soluble in water, but insoluble in kerosene. The property of a substance of getting dissolved, is called its solubility.
Let’s try this.
Take a piece of copper or aluminum wire or a small nail. Hammer it repeatedly. What do you observe?
Answer: On hammering repeatedly, the wire becomes flat, i.e., it forms a thin sheet. Metals can be converted into sheets by hammering. This property of metals is called malleability.
Can you tell?
1. Why are the electric boards fitted on the wall made of plastic or wood?
Answer: Plastic and wood are bad conductors of electricity. Therefore the electric boards fitted on the walls are made of plastic or wood so that the electric current does not pass and the person touching the switch does not get an electric shock.
2. The handle of a cooker is made of plastic. Why?
Answer: The body of the cooker is made of metal. Metal is a good conductor of heat. When the cooker is placed on the stove, the whole body of the cooker gets heated. Plastic is a bad conductor of heat. Therefore the handle of the cooker is made of plastic so that the person can hold it without getting burnt.