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Std 6 General Science · Chapter 6

6. Properties of Substances

Complete solutions to the Exercises. Maharashtra State Board (Balbharati), Grade Six General Science.

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About the chapter

Every substance has some properties. This chapter tells us about the states of matter: solid, liquid and gas. We learn about mass, volume and density. We also learn how light passes through different substances.

Key points

  • The particles of a solid are held tightly. A solid has a fixed shape.
  • A liquid takes the shape of its container.
  • A gas spreads and fills all the space available.
  • A substance can change its state on heating or cooling.
  • Density = Mass ÷ Volume.
  • Oil floats on water because its density is less than that of water.

Words to remember

  • mass – the quantity of matter in an object
  • volume – the space taken up by an object
  • transparent – a substance that lets light pass through fully
  • translucent – a substance that lets light pass through partly
  • opaque – a substance that does not let light pass through

Exercises

1Choose the correct option and complete the sentences.

(a) Ice is the solid state of water.

(b) When light rays fall on an opaque substance, light does not pass through.

(c) Oil floats on water; this means the density of oil is less than water.

2Which of the following statements represent the solid and gaseous states respectively?

Solid state: (a) Particles are very close to each other and hold each other tightly.

Gaseous state: (c) Particles scatter everywhere in the available space.

Solid stateLiquid stateGas stateheld tightly in fixed placesloosely bound, they flowfree, they fill the spaceThe substance stays the same — only the hold between its particles changes. This is called a change of state.

Arrangement of particles in solid, liquid and gas.

3Observe the relationship in the first pair and complete the second pair.

(a) Glass : Transparent substance :: Butter paper : Translucent substance

(b) Solid : Has a specific shape :: Liquid : takes the shape of the container

4Stand close to the mirror and look at your face. Now exhale onto the mirror. What difference do you see? What could be the reason for it?

Observation: The mirror becomes misty and the face is not seen clearly. After a while, it becomes clear again.

Reason:

  1. Our breath contains water vapour.
  2. The mirror is cooler than our breath.
  3. The vapour turns into tiny water drops on the mirror.
  4. These drops make the mirror misty.
  5. Later the drops evaporate and the mirror becomes clear.
5There are two boxes of the same size. One is filled with stones and the other with small pieces of sponge. Without opening the boxes, how will you identify which box contains what?
  1. Lift both the boxes.
  2. The heavier box contains stones.
  3. The lighter box contains sponge.
  4. Both boxes have the same volume.
  5. But stone has more density than sponge.

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6Identify the group in which all the substances are in the liquid state.
  • (a) Stone, water, smoke
  • (b) Milk, oil, sherbet  — correct
  • (c) Air, iron, steam
7From the following, which are transparent and which are translucent? Make two separate lists. Piece of glass, butter paper, notebook-cardboard, plastic sheet, sandpaper, oiled paper.

Transparent: Piece of glass, plastic sheet

Translucent: Butter paper, oiled paper

Notebook-cardboard and sandpaper are opaque.

8Onion fritters (Kanda-bhaji) are being made in the neighbour’s house and you came to know this without going there. What is the connection between this and the states of matter?
  1. While frying, some particles of onion and oil turn into gas.
  2. Gas particles are free and spread in all directions.
  3. They travel through the air and reach our nose.
  4. So we smell the bhaji from far away.
9If a liquid has a volume of 3 ml and a mass of 7.5 grams, what will be its density?
Density = Mass ÷ Volume
= 7.5 g ÷ 3 cm³
= 2.5 g/cm³

The density of the liquid is 2.5 g/cm³.

10A different type of glass is used for windows in newly constructed buildings. From outside during the day these look like coloured mirrors and objects inside cannot be seen, but those inside can see outside. What should these glasses be called: Transparent, Opaque or Translucent?

This glass is transparent.

  1. Light passes through it. So people inside can see outside clearly.
  2. It has a shiny coating that reflects bright sunlight.
  3. So from outside, it looks like a mirror during the day.
11A thin dark film is stuck to car windows. What happens due to this?
  • (a) The glass becomes more transparent.
  • (b) The glass becomes opaque.
  • (c) The glass becomes translucent  — correct

The film lets only a little light pass through.

12Which one will have a greater volume, 1 kg cotton or 1 kg of iron?

1 kg of cotton will have the greater volume.

  1. Both have the same mass.
  2. Cotton has very low density.
  3. So cotton takes up much more space than iron.
13If 1 kg of cotton and 1 kg of iron are placed in the two pans of a balance scale, which pan will go down?

Neither pan will go down. Both have the same mass of 1 kg. So the balance stays level.

14Several measuring instruments are shown in the picture. Make two separate groups of instruments that measure volume and mass. Which of these instruments must be transparent and why?

Measure volume: Measuring cylinder, syringe

Measure mass: Pan balance, beam balance, spring balance, weighing scale

Must be transparent: the measuring cylinder and the syringe. We must see the liquid level inside to read the volume.

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