# Extra Questions For Class 9 Science Chapter 1 Matter in Our Surroundings

#### Very Short Answer Type Questions (One Mark Each)

Q.1. Degree Celsius and Kelvin are two units of measuring temperature. Which of these are SI and non-SI units ?

Answer Ans. Degree Celsius – Non-SI. Kelvin – SI.

Q.2. What is the SI unit of pressure ?

Q.3. Define matter.

Answer Ans. Matter may be defined as some thing that occupies space, possesses mass and offers resistance to any stress.

Q.4. Which of the following is/are a matter :
Apple, biscuit, coffee, toffee, soil, soyabean oil, cold drink, ice-cream, tooth paste, scent, dust, wind and shoe?

Answer Ans. All are various types of matter.

Q.5. Name a simplest form of matter.

Answer Ans. Element is the simplest form of matter. For example, iron.

Q.6. What is common about all things which we see around us ?

Answer Ans. All things occupy space i.e., have volume and possess mass.

Q.7. Name different states of water.

Answer Ans. Water can exist in three states of matter as: Ice (solid), water (liquid), and water vapour (gas)

Q.8. What is the common unit of measuring volume ?

Answer Ans. Common unit of measuring volume is litre (L), 1 L = dm3, 1 L = 1000 mL, 1 ml=1 cm3

Q.9. What is mL ?

Answer Ans. It is mililitre, 1 ml-1 cm3 and 1000 mL-1 litre.

Q.10. Is it correct to say that matter is particulate in nature ?

Answer Ans. Yes. It consists of particles.

Q.11. Kitchen salt (NaCl) when added to water, gets evenly distributed in it. Which characteristic of particles of matter is exhibited by this?

Answer Ans. It shows that there is enough space between the particles of matter.

Q.12. Which has more force of attraction between the particles ? Iron nail or rubber band.

Answer Ans. Rubber band can expand on stretching while iron nail cannot. Hence iron nail has more force of attraction between the particles.

Q.13. Which will have more density – a solid or a liquid ? Explain.

Answer Ans. A solid has more density than a liquid because particles are much closer to one another in a solid than in a liquid.

Q.14. Which are more energetic solids or liquids ?

Answer Ans. Liquids. The molecules in a liquid are mobile. Therefore they have more kinetic energy.

Q.15. In which physical state, water exists at (a) 100 °C (b) 0 °C ?

Answer Ans. (a) Liquid and vapour.
(b) Solid and liquid.

Q.16. Is freezing point of water and melting point of ice the same ? Say yes or no.

Q.17. What is the freezing point of water ?

Answer Ans. 0 °C or 273 K.

Q.18. What is the melting point of ice ?

Answer Ans. 0 °C or 273 K.

Q.19. The boiling point of water is 100 °C. Express this in SI units (Kelvin scale).

Answer Ans. Temperature on Kelvin scale = Temperature on Celsius scale +273= 100+273=373 K.

Q.20. The boiling point of alcohol is 78 °C. What is this temperature on Kelvin scale ?

Answer Ans. Temperature on Kelvin scale = Temperature on Celsius scale +273 = 78 +273 = 351 K.

Q.21. The Kelvin scale temperature is 0 K. What is the corresponding Celsius scale temperature ?

Answer Ans. Temperature on Celsius scale = Temperature on Kelvin scale-273=0-273-273°C.

Q.22. Why does a gas exert pressure ?

Answer Ans. Gas molecules are in a state of constant random motion. They collide with the walls of the container exerting a steady force which results in the form of pressure of the gas.

Q.23. How will you demonstrate that water vapour is present in air ?

Answer Ans. The formation of drops of water on the outside surface of the tumbler containing crushed ice confirms the presence of water vapour in air.

Q.24. Why gases are compressive but not liquids ?

Answer Ans. There is lot of empty space between the molecules in the gaseous state. On applying pressure, the molecules come closer and the is compressed.

Q.25. Which produces more severe burns : boiling water or steam at 100 °C ?

Answer Ans. Steam at 100 °C produces more severe burns because it contains greater amount of heat than the boiling water at 100 °C by an amount equal to latent heat of vaporisation.

Q.26. Arrange the following substances in increasing order of force of attraction
between the particles :
(a) Milk
(6) Salt and
(c) Oxygen

Answer Ans. Force of attraction is maximum in solids followed by liquids followed by gases. Therefore, increasing order of force of attraction is:
Oxygen < Milk < Salt

Q.27. A substance has no mass. Can we consider it as matter? [CBSE 2012]

Answer Ans. No matter always possesses a definite mass.

Q.28. If the food is being cooked in the kitchen, name the process which brings smell to us?

Answer Ans. The smell comes to us by the process of diffusion.

Q.29. Name the phenomenon by which particles of two or more substances intermix on their own.

Answer Ans. It is the phenomenon of diffusion.

Q.30. A diver is able to cut through water in a swimming pool. What property of matter does this observation show ?

Q.31. Sugar and salt when kept in different jars take the shape of the jar. Are they solid ? Justify your answer.

Answer Ans. They are solids because the shape of each individual sugar or salt crystal remains fixed.

Q.32. What determines the state of a substance ?

Answer Ans. State of a substance (solid, liquid or gas) is determined by the force of attraction between the molecules of a substance.

Q.33. Name two gases which are supplied in compressed form in homes and hospitals.

Answer Ans. LPG is supplied in homes and oxygen in hospitals in compressed form.

Q.34. State one difference between gas and vapour.

Answer Ans. Gas refers to a substance that exists as gas at room temperature. Vapour refers to the state of the substance for example water vapours or iodine vapours.

Q.35. After morning exercise, you feel cold. Explain.

Answer Ans. The sweat produced during exercise is evaporated causing cooling,

Q.36. Give the graphical representation of the temperature and time when a student heats a mixture of ice and water in a beaker.

Answer Since ice and water are in equilibrium, the temperature would be zero. When we heat the mixture, energy supplied is utilized in melting the ice and the temperature does not change till all the ice melts because of latent heat of fusion. On further heating, the temperature of the water would increase.

#### Short Answer Type Questions (Two Marks Each)

Q.1. (a) Write the full forms of (1) LPG (1) CNG.
(b) Give the main use of CNG.

Answer Ans. (a) (1) LPG stands for Liquefied Petroleum Gas.
(i) CNG is Compressed Natural Gas.
(b) CNG filled in cylinders is used as a fuel to run vehicles like cars, buses, etc.

Q.2. Define diffusion. Is it faster in winter or summer season ?

Answer Ans. The phenomenon of intermixing of particles of different types of matter, on their own, is called diffusion. The process of diffusion becomes faster with an increase in temperature due to increase in kinetic energy of moving particles. Hence, diffusion is faster in summer than in winter

Q.3. By placing finger in the running stream of water, you are not able to break
the stream of water. What do you conclude from this ?

Answer Ans. From this we conclude that:
(i) There is force of attraction between the particles of matter.
(ii) The force of attraction keeps the particles together in the matter.

Q.4. In which of the following substances, you expect strongest and in which the
weakest molecular forces : (a) Sodium chloride (b) Carbon dioxide ?

Answer Ans. (a) Sodium chloride (NaCl) being a solid has very strong molecular forces.
(b) Carbon dioxide (CO2) being a gas has the weakest molecular forces.

Q.5. What is the common name of solid carbon dioxide ? What is its use?

Answer Ans. Solid carbon dioxide is commonly known as dry ice. It is extremely cold substance. It is used to preserve perishable food like meat, poultry, ice-cream etc. These days it is also used to create stage effects.

Q.6. Name the factors affecting evaporation.

Answer Ans. Following are the factors which affect evaporation of liquids :
(i) Surface area
(ii) Temperature
(iii) Humidity
(iv) Speed of wind.

Q.7. Liquids like ether and acetone are kept in cool places. Why?

Answer Ans. Ether and acetone have low boiling temperature and are highly volatile. They are kept in cool places. If they are not kept in cool places :
(i) these liquids will evaporate very fast,
(ii) the pressure inside the bottle may increase due to which the bottle may break.

Q.8. Which will evaporate faster : alcohol or ether?

Answer Ans. Ether has a lower boiling temperature than alcohol. This is becuase the intermolecular forces of attraction between the molecules of ether are weaker than that of alcohol. Consequently, ether will evaporate faster than alcohol.

Q.9. Boiling point of water on hill station like Simla is lower than in Delhi. Why?

Answer Ans. Boiling point of a liquid is the temperature at which its vapour pressure becomes equal to the atmospheric pressure. The atmospheric pressure on hill stations like Simla is less than in Delhi. Hence, the vapour pressure of water becomes equal to atmospheric pressure at low temperature. So the boiling point of water is lower on mountains than in Delhi.

#### Long Answer Type Questions (Five Marks Each)

Q.1. Wet clothes dry up similarly when we spill water on the floor it dries up
after sometime. In both the cases change of state from liquid to vapour takes place
without reaching the boiling point.
(i) What is this phenomenon called ?
(ii) Explain how the change occurs at temperatures lower than the boiling
(ii) Mention three factors which determine the rate at which the change of
state from water to vapours occurs at room temperature.

Answer Ans. (i) This phenomenon is called evaporation.
(ii) Molecules of water which are moving at speed higher than the average speed leave the surface and go into the atmosphere. This is how evaporation takes place.
(iii) Factors that determine the rate of evaporation :
(a) Surface Area – Greater the surface area, greater will be the rate of evaporation.
(b) Temperature – Higher the temperature, greater will be the rate of evaporation.

Q.2. Explain the following :
(i) Fusion (ii) Kelvin (iii) Latent heat (iv) Latent heat of fusion and vaporisation (v) Atmospheric pressure.

Answer Ans. (i) Fusion : The process of melting i.e., conversion of solid into liquid state is called fusion.
(ii) Kelvin : Kelvin is the SI unit of temperature. 0 °C = 273.16 K.
For the sake of convenience 0 °C is taken equal to 273 K. Thus,
Temperature in Kelvin (K) = Temperature in Celsius (°C) + 273.
(iii) Latent heat: On heating a solid to liquid (fusion) or liquid to gas (evaporation), the heat energy is used up to overcome the force of attraction between the particles without showing any change in temperature. Since this heat energy is hidden in the bulk of the matter, it is called latent heat. The word latent means hidden.
(iv) Latent heat of fusion : The amount of heat energy needed to convert one kg (1000 g) of a solid into liquid at the atmospheric pressure at its melting point is called latent heat of fusion. Latent heat of vaporisation : The amount of heat energy needed to convert 1000 mL of water into vapours at its boiling point is called latent heat of vaporisation.
(v) Atmospheric pressure : The pressure of air in atmosphere is known as atmospheric pressure.
At sea level, the atmospheric pressure is 1 atmosphere which is called normal atmospheric pressure.
1 atmosphere = 1.01 x 105 Pascals

Q.3. (i) Why do solids have fixed shape and fixed volume ?
(ii) Why is air dense at the sea level ?
(iii) On melting of ice, there is decrease in volume instead of increase. Why?
(iv) What is the binding force between molecules if a substance is a gas under ordinary conditions of temperature and pressure ?
(v) Why are average kinetic energies of hydrogen, carbon dioxide and ethane the same at the same temperature ?

Answer Ans. (i) In solids, the particles are closely packed and their positions are fixed due to strong forces of attraction existing between them. So, solids have fixed shape. Since, the space between the particles are also fixed, the solids have fixed volume.
(ii) Air at sea level is compressed by the mass of air above it. Hence, air is more dense at sea level than at an altitude.
(iii) There are empty spaces in the packing of water molecules in ice. On heating different strings of hydrogen bonded water molecules break and water molecules come closer to each other. Hence, the volume decreases on melting of ice.
(iv) The binding force between the molecules of a gas is van der Waals force.
(v) Average kinetic energy of any gas is directly proportional to its absolute temperature. Since all the gases are at the same temperature, their average kinetic energies will also be the same.

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