Substances in the Surroundings –Their States and Properties- Standard 6 - General Science - Balbharati

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Substances in the Surroundings –Their States and Properties

Exercise

Q. 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.


Q. 2 Discuss.

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

Ans. When Riya pours water from her bottle into another bottle, the shape of the water changes. This is because water is a liquid and does not have a fixed shape. It takes the shape of the container it is in. So, in the new bottle, the water will fit its shape.

(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. When Halima picks up a stone and puts it in a dish of water, the shape of the stone does not change. This is because a stone is a solid and has a fixed shape. It does not flow or take the shape of the container. It will stay the same no matter where you put it.

Q. 3 Write the properties of these substances.

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

Ans. 

1. Water
  • Fluidity: Water flows easily on a slope.
  • Solubility: Many substances like salt and sugar dissolve in water.
  • Transparency: Clean water is transparent.

2. Glass

  • Transparency: Glass is a transparent substance.
  • Brittleness: It breaks into pieces when pressure is applied.
  • Lustre: Has a shiny surface.

3. Chalk

  • Brittleness: Breaks easily into powder when pressed.
  • Hardness: Less hard, easily scratched or broken.

4. Iron Ball

  • Hardness: Very hard and strong.
  • Density: Heavier than many other substances of the same size.
  • Conductivity: Good conductor of heat and electricity.
  • Sonority: Produces a ringing sound when struck.
  • Malleability and Ductility: Can be hammered into sheets or drawn into wires.

5. Sugar

  • Solubility: Soluble in water, but not in kerosene.
  • Transparency: Crystals are slightly transparent.
  • Hardness: Can break into smaller crystals, not very hard.

6. Salt

  • Solubility: Easily dissolves in water, not in kerosene.
  • Hardness: Brittle; can break into fine particles.

7. Flour

  • Solubility: Does not dissolve in water; it mixes but remains visible.
  • Hardness: Very soft and fine.

8. Coal

  • Brittleness: Breaks into pieces when pressed.
  • Hardness: Hard but brittle.
  • Opacity: Not transparent.

9. Soil

  • Hardness: Loose and soft, can be pierced easily.
  • Solubility: Does not dissolve in water.
  • Opacity: Not transparent.

10. Pen (Plastic part)

  • Hardness: Hard and strong.
  • Transparency: Usually opaque (not see-through).
  • Elasticity: Some parts may bend slightly but don’t return to shape like rubber.

11. Ink

  • Fluidity: Flows like a liquid.
  • Solubility: Mixes with water (water-soluble ink).
  • Transparency: Colored but may allow some light to pass.

12. Soap

  • Solubility: Dissolves in water.
  • Softness: Can be pressed or shaped.
  • Transparency: Usually opaque, but some soaps may be transparent.
Q. 4 What is sublimation? Write the names of everyday substances that sublimate.

Ans.  Sublimation is the process in which a solid changes directly into a gas or vapour without first becoming a liquid.

Examples of everyday substances that sublimate:

  • Iodine

  • Camphor

  • Naphthalene balls

  • Dry ice (solid carbon dioxide)


Q. 5 What is it made from? Why?

(a) A sickle to cut sugarcane is made from iron or steel because these materials are hard, strong, and can be sharpened to cut crops easily.

(b) The sheets used for roofing are made from tin, aluminium, or asbestos because they are strong, do not rust easily, and protect against rain and sun.

(c) A screwdriver is made from steel because it is very hard and does not bend or break while turning screws.

(d) A pair of tongs is made from iron or steel as they are strong and can handle hot objects without getting damaged.

(e) Electric cables are made from copper or aluminium wires because they conduct electricity well, and are covered with plastic to prevent electric shock.

(f) Ornaments are made from gold, silver, or other shiny metals because they have a bright appearance (lustre) and can be shaped easily into beautiful designs.

(g) Pots and pans are made from stainless steel, aluminium, or copper because these materials conduct heat well and are suitable for cooking.

Q. 6 What will happen if….? And why?

(a) Nails are made of plastic.

Ans. They will bend or break easily and won’t go into wood or walls properly, because plastic is not hard or strong like metal.

(b) A bell is made of wood.

Ans. It will not make a clear ringing sound, because wood is not sonorous like metal.

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

Ans. It will be difficult to hold hot objects, and hands might get burnt, because metal conducts heat but rubber does not.

(d) A knife is made of wood.
Ans. It will not cut anything, because wood is soft and cannot have a sharp edge like metal.

(e) An axe is made of rubber.
Ans. It will not be able to cut wood or anything hard, because rubber is soft and flexible, not strong or sharp like metal.

Q.7 Who am I?

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

Ans. I am mercury, because mercury is used in thermometers to measure temperature.

(b) I make things hot or cold.
Ans. I am heat, because heat can increase or decrease the temperature of things.

(c) I have no shape whatsoever!
Ans. I am a gas, because gases do not have a fixed shape and take the shape of the container.

(d) I dissolve in water, but not in kerosene.
Ans. I am salt, because salt is soluble in water but insoluble in kerosene.

Q.8 Why does this happen?

(a) Coconut oil thickens in winter.
Ans. This happens because the temperature is low in winter, and coconut oil changes from liquid to solid form when it gets cold.

(b) Kerosene left open in a dish disappears.
Ans. This happens because kerosene evaporates slowly when kept in the open air.

(c) The fragrance of incense sticks lighted in one corner of a room spreads to the other corner.
Ans. This happens because gases spread in all directions and mix with the air.

(d) What you see in the picture.

Fig. Q.8(d)


Ans. In the picture, the yellow ball floats and the red object sinks. This happens because the yellow ball has less density than water, so it floats. The red object has more density than water, so it sinks.

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