Ch.5: Substances in the Surroundings - Their States and Properties

Substance in the Surroundings - Their States and Properties | Class 6 | Science | Chapter 5 | Maharashtra State Board

Welcome to this educational video on the properties and states of substances. This video is designed to help you gain a deeper understanding of the various substances in our surroundings, their properties, and how they change states. In this video, we will conduct experiments to demonstrate the different states of substances, including how they change from solid to liquid and gaseous states. We will also learn about the concept of temperature and thermometers and provide examples to help you better understand how temperature affects the properties of substances. We will explore in-depth the boiling, freezing, and sublimation of substances, and we will showcase various activities that demonstrate the unique properties of different substances. Additionally, we will delve into the various properties of substances, such as their strength, conductivity, and malleability. Finally, we will conclude the video by discussing metals and their unique properties. By the end of this video, you will have a comprehensive understanding of the different substances in our environment, their properties, and how they can be transformed through changes of state. You will also have a better appreciation for the role that temperature plays in these transformations, as well as a deeper understanding of metals and their properties.

Questions & Answers

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 ( 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. Dicuss.

(a) Riya pours some water from her bottle into another bottle. Does it change the shape of the water ?

Ans. Yes, the shape of water changes 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 ?

Ans. No, the shape of the stone does not change. Stone is a solid, hence retains its shape.

3. Write the properties of these substances.

Water, glass, chalk, iron ball, sugar, salt, flour, coal, soil, pen, ink, soap.

	Substance	State	Properties
1.	Water	Liquid	Fluidity, density, solubility, transparency, thermal conductivity.
2.	Glass	Solid	Brittlness, hardness, density, transparency.
3.	Chalk	Solid	Brittlness, 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	Brittlness, hardness, density, solubility.

4. What is sublimation? Write the names of everyday substances that sublimate.

Ans. The change of a solid substance directly into a gas or vapour without first changing into liquid is called sublimation.

• Substances that sublimate: Camphor, naphthalene balls, ammonium chloride, iodine.

5. What is it made from? Why?

(a) A sickle to cut sugarcane.

Ans. A sickle is made of iron. An iron sickle is hard and malleable. When sharpened it will be able to cut the hard sugarcane.

(b) The sheets used for roofing.

Ans.

1. The sheets used for roofing are made of plastic, aluminium.

2. Plastic is hard, hence, protects against weather conditions.

3. Plastic is transparent, hence, sunlight can pass through it.

4. Aluminium is hard, light weight and durable, hence, protects against all weather conditions.

5. Malleable hence formed into thin sheets.

(c) A screwdriver.

Ans.

1. A screwdriver is made up of iron, steel, aluminium.

2. A screwdriver possesses property of hardness hence, it easily pierces a screw in piece of wood, wall, metals etc.

(d) A pair of tongs.

Ans.

1. A pair of tongs are made up of iron, steel aluminium etc. Tongs are used to lift hot, boiling utensils or vessels.

2. Tongs are hard, ductile and malleable.

3. Hence, have strong grip to hold utensils.

4. Rubbers fitted on the ends will protect from thermal conduction, from burns.

(e) Electric cables.

Ans.

1. Electric cables are metal wires (thin) wound in plastic.

2. Metal wires possess the property of hardness, ductility, electrical conductivity.

3. Plastic /rubber covering possesses the property of hardness, elasticity and are bad conductors of heat and electricity.

(f) Ornaments.

Ans.

1. They are made up of metals like gold and silver.

2. They possess the property of hardness, ductility, malleability, lustre.

(g) Pots and pans.

Ans.

1. They are used to cook food, hence metals like aluminium, steel are used.

2. They possess the property of hardness, ductility, malleability, thermal conductivity, electrical conductivity, (microwave ovens)

6. What will happen if….? And why?

(a) Nails are made of plastic.

Ans. If nails are made of plastic, they will not be able to pierce through other substances on being pushed or forced by a hammer. Plastic lacks the property of hardness.

(b) A bell is made of wood.

Ans. If a bell is made of wood it will never make a ringing sound. A wooden bell does not have the property of being sonorous. Sonority is the property of metals to produce a ringing sound.

(c) Rubber is not fitted on a pair of tongs.

Ans. Pair of tongs are made up of metals which conduct heat and electricity. They have property of thermal conduction and electrical conduction. Rubber is a bad conductor of heat and electricity. It will not allow heat to pass to the hands/handle of the tongs, thus protecting us. If rubber is not fitted on a pair of tongs, we will not be able to lift hot objects with it.

(d) A knife is made of wood.

Ans. Wood does not have the property of malleability. Therefore, the edge of wooden knife will be blunt. Hence, we will not be able to cut anything with it.

(e) An axe is made of rubber.

Ans. If an axe is made of rubber, it will not be used to cut wood or tree. Rubber does not have the property of hardness that is required to push through to cut it.

7. Who am I?

(a) I’m found in a thermometer; I measure your temperature.

Ans. Mercury.

(b) I make things hot or cold.

Ans. Heat.

(c) I have no shape whatsoever!

Ans. Liquid, gases.

(d) I dissolve in water, but not in kerosene.

Ans. Salt.

8. Why does this happen?

(a) Coconut oil thickens in winter.

Ans. Coconut oil is in liquid state. In winter the surrounding temperature / atmospheric temperature starts decreasing. Coconut oil starts cooling or losing heat, it changes to solid state. Thus coconut oil thickens in winter.

(b) Kerosene left open in a dish disappears.

Ans. When kerosene is left open in a dish, it is exposed to surrounding temperature. As the temperature is more, kerosene starts continuously evaporating and finally disappears.

(c) The fragrance of incense sticks lighted in one corner of a room spreads to the other corner.

Ans. The fragrance of incense sticks is given out in the form of scented vapours. As vapours are in gaseous state, the gas molecules spread out in the room. The molecules of gas move very fast and there are no forces to stop them from going apart. Therefore, the fragrance of incense sticks lighted in one corner of room spreads to the other corner.

(d) What you see in the picture.

Ans. The mass of balloon is less than an apple. This difference is because of their densities. Since, an apple has greater density, it will sink to the bottom on other hand the balloon has lesser density, it will float over water surface.

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E X T R A

1. Match the columns.

​Column 'A'	Answer	Colum 'B'
Boiling water	100°C	> 35°C
Body temperature	37°C	0°C
Freezing water	0°C	< 5°C
Air (summer afternoon)	> 35°C	< 15°C
Inside fridge	< 5°C	< -18°C
Air (winter night)	< 15°C	100°C
Inside the freezer	< -18°C	37°C

2. Answer in one sentence.

(a) What is change of state of substances?

Ans. When a substance changes from one state to another, the process is called change of state of the substance.

(b) What happens when a substance gains heat?

Ans. When a substance gains heat, it changes its state i.e. from solid to liquid and liquid to gas.

(c) What happens when a substance loses heat?

Ans. When a substance loses heat, it changes its state from gaseous to liquid and liquid to solid state.

(d) How do we tell how hot or cold a substance is?

Ans. The temperature on the thermometer will tell us how hot or cold a substance is.

(e) What is condensation?

Ans. When vapour cools, it is converted into liquid again. This process is condensation.

(f) At what temperature condensation of steam takes place?

Ans. Condensation of steam takes place at 100°C.

(g) What is brittleness?

Ans. Some substances break into small pieces or particles. Such substances are said to be brittle. This property of substances is called brittleness.

(h) What is hardness?

Ans. The hardness of a substance is determined by how much resistance it offers to the substances being pushed through it.

(i) What is elasticity?

Ans. 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.

(j) What is fluidity?

Ans. Liquids flow downward on a sloping surface. This property is called fluidity.

(k) How is fluidity of any liquid determined?

Ans. Fluidity of any liquid is determined by how easily it flows.

(l) What is density?

Ans. The mass of different substances having the same volume can be different. This difference is because of the difference in their densities. Between substances of the same volume, the ones with greater density are heavier than those of lesser density.

(m) What is solubility?

Ans. The property of a substance of getting dissolved is called its solubility.

(n) What is transparency?

Ans. When we can look through a substance and see things on the other side, then that substance is said to be transparent. This property of the substances is called transparency.

(o) What are metals?

Ans. Metals are substances like copper, gold, iron, aluminium. They are found in the form of minerals deep inside the earth. Minerals from the earth’s crust are processed to obtain metals.

(p) What is malleability?

Ans. Metals can be converted into sheets by hammering. This property of metals is called malleability.

(q) What is ductility?

Ans. Metals can be stretched and drawn into thin wires. This property of metals is called ductility.

(r) Name some ductile metals.

Ans. Metals like silver, gold, platinum can be drawn into fine wires.

(s) What is electrical conduction?

Ans. Electricity flows through metals. All metals are conductors of electricity to a greater or lesser extent.

(t) What is thermal conductivity?

Ans. Metals allow heat to flow through them. This property is called thermal conductivity

(u) What is lustre?

Ans. The typical shine or characteristic colour by which metal can be identified is called lustre.

(v) What is sonority of metals?

Ans. Metals produce a ringing sound. This property is called the sonority of metals.

3. Give scientific reasons for following.

(a) Metals are used to make musical instruments.

Ans. Metals possess the property of being sonorous, i.e. produce a ringing sound. Hence, they are used to make musical instruments.

(b) Ornaments are made up of metals.

Ans. Metals have the property of being malleable, ductile, lustrous. Hence, ornaments are made up of metals.

(c) Why should we not put our hand or finger in the water to judge the hotness of water?

Ans. We should never put our hand or finger in the water to judge how hot it is because that is not an accurate measure. Besides if the substance is very hot, we could get scalded.

4. Can you tell ?

(a) Why are electric boards fitted on the wall made of plastic or wood?

Ans. Plastic or wood are bad conductors of heat and electricity. Electric boards are made up of plastic or wood. So that while touching we will not get electric shock.

(b) How can we change the volume of a gas?

Ans. On changing the pressure on a gas in a closed container we can change its volume.

(c) The handle of cooker is made of plastic. Why?

Ans. Cooker is made of metal. When food is cooked in it, it gets heated and the whole of its body becomes hot due to thermal conductivity. Hence with the plastic handle we can easily lift the hot cooker as plastic is a bad conductor of heat.

5. List properties.

(a) List properties of solids

Ans. Solids have its own shape i.e. Retains shape, no matter how it is kept. Solids have definite volume. e.g. Sand when poured on a flat surface form a heap.

(b) List properties of liquids.

Ans. Liquid does not have a shape of its own. Takes the shape of the container. A liquid has a specific volume i.e. occupies definite portion of a container. Liquids. e.g. water, milk, kerosene.

(c) List properties of gases.

Ans. Gases does not have a shape of its own. Occupies all the available space. Does not have a definite volume. e.g. Air.

(d) List various uses of changes in physical state.

Ans. Candles are made by melting paraffin wax.

Solid carbon-dioxide (dry ice) is used to make ice-cream and to keep it frozen.

Liquid nitrogen is used in animal husbandry.

Sand (silica) is melted to make glass.

Metals like gold and silver are melted to make ornaments.

Iron is melted to make tools.

(e) List properties of substances.

Ans. The properties of substances are:

• Brittleness

• Hardness

• Elasticity

• Fluidity

• Density

• Solubility

• Transparency

(f) List properties of metals.

Ans. The properties of metals are:

• Malleability

• Ductility

• Electrical conductivity

• Thermal conductivity

• Lustre

• Sonority

6. Explain.

(a) Explain with example how liquids take the shape of the surface.

Ans. Liquids have a specific volume. They occupy definite portion of a container. Liquids spreads on a flat surface on pouring. Liquids flow downwards along a slope.

(b) Explain. Boiling point and condensation point of water are one and the same.

Ans. Water boils at 100°C. i.e. boiling point of water is 100°C. Condensation of steam also takes place at 100° C. Thus, boiling point and condensation point of water are one and the same.

(c) Explain Ebullition.

Ans. As the water gets heated, its temperature increases and it evaporates at a faster and faster rate. When water kept on a stove attains a particular temperature or level of heat, then evaporation takes place in all parts of the body of water. Then we see water bubbles rising at a faster and faster rate to the surface and steam mixing in the air. This is called boiling of water or Ebullition.

(d) Freezing point of water.

Ans. Water kept in a fridge or on ice becomes cooler and cooler i.e. its temperature falls. At a certain temperature water does not cool further but starts freezing and forms ice. The temperature at which this happens is called the freezing point of water (0°C).

(e) Freezing point and melting point of water are same.

Ans. The temperature at which water does not get any cooler but starts freezing and forming ice is 0°C. When ice gets heat, it starts melting or changes into liquid state at 0°C. Thus, freezing point and melting point of water are one and the same.

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