NCERT Solutions for Class 9 Science Chapter 14 Natural Resources.

Notes on Matter in our Surroundings

1.  Matter- Matter is anything which occupies space and has mass is called matter. Air and water, sugar and sand, hydrogen and oxygen etc. Matter is made up of very small tiny particles. Particles of matter have space between them they attract each other.

2.  Classification- On the basis of physical properties, matter is classified as solids, liquids and gases. On the basis of chemical properties, matter is classified as elements, compounds and mixtures.

      •  Solids- Solids have strong molecular force and a definite shape and size solids can neither flow nor be compressed.

      •  Liquids- Liquids have weak intermolecular flow and large intermolecular spaces. Liquids do not have a definite shape but can flow.

      •  Gases- Gases have weak intermolecular flow, high compressibility, and no definite shape and volume.

3.  Physical properties of matter- Matter is made up of particles which are very small in size. Everything around us is made up of tiny pieces or particles. The particles of matter are constantly moving (they are in motion).The particles which make up matter are atoms and molecules.

4.  Interchange in states of matter- Matter can change its state in solid, liquid or gas depending upon the type of matter.

5.  Diffusion- The mixing of a substance with another substance due to the motion or movement of its particles is called diffusion. It is one of the properties of materials. The diffusion of one substance into another substance goes on until a uniform mixture is formed. Diffusion takes place in gases, liquids and solids.

6.  Latent heat- Latent heat is the heat energy which has to be supplied to change the state of a substance. Latent heat does not increase the temperature of a substance. But latent heat has to be supplied in order to change the state of a substance. Latent heat can be of fusion or of vaporization.

7.  Sublimation- The changing of a solid directly into vapours on heating and of vapours into solid on cooling, is known as sublimation. When these solid substances are heated, their particles move quickly and they separate completely to form vapor (or gas). Similarly when these vapor (or gas) is cooled, these particles slow down so quickly that they become fixed and form a solid.

8.  Evaporation- The process of conversion of a liquid into vapour (or gas) at its boiling point is called evaporation. Some particles in liquid always have more kinetic energy than the others. So, even when a liquid is well below its boiling point, some of its particles have enough energy to break the forces of attraction between the particles and escape from the surface of the liquid in the form of vapour. Thus the fast moving particles of a liquid are constantly escaping from the liquid to form vapor or gas. Temperature, surface area of liquid, humidity, and wind speed are fators that affect evaporation. Evaporation causes cooling effect.

9.  Effect of Change of Pressure: The physical state of matter can also be changed by increasing or decreasing the pressure to it. Gases can be liquefied by applying pressure and lowering temperature. When high pressure is applied to a gas, it gets compressed, and when in addition to it we lower its temperature, it gets converted into liquid. So, we can also say that gases can be turned into liquids by compression and cooling.

Q1.  Convert the following temperatures to the Celsius scale.

      (a)   293 K

(b)   470 K.

Ans.   (a)   293 K into °C

                     293 273 = 20°C

             (b)   470 K into °C

                     470 273 = 197°C

Q2.  Convert the following temperatures to the Kelvin scale.

      (a)   25°C

(b)   373°C.

Ans.   (a)   25°C into K

                     25 + 273 = 298 K

             (b)   373°C into K

                     373 + 273 = 646 K

Q3.  Give reason for the following observations.

      (a)   Naphthalene balls disappear with time without leaving any solid.

      (b)   We can get the smell of perfume sitting several metres away.

Ans.   (a)   Naphthalene balls disappear with time without leaving any solid, because naphthalene balls sublime and directly changes into vapour state without leaving any solid.

             (c)   We can get the smell of perfume sitting several metres away because perfume contain volatile solvent and diffuse faster and can reach people sitting several metres away.

Q4.  Arrange the following substances in increasing order of forces of attraction between the particles water, sugar, oxygen.

Ans.   Oxygen water sugar.

Q5.  What is the physical state of water at

      (a)   25°C

      (b)   0°C

      (c)   100°C

Ans.   (a)   25°C is liquid

(b)   0°C is solid or liquid

              (d)   100°C is liquid and gas

Q6.  Give two reasons to justify

      (a)   water at room temperature is a liquid.

      (b)   an iron almirah is a solid at room temperature.

Ans.   (a)   Water at room temperature is a liquid because its freezing point is 0 °C and boiling point is 100 °C.

              (c)   An iron almirah is a solid at room temperature because melting point of iron is higher than room temperature.

Q7.  Why is ice at 273 K more effective in cooling than water at the same temperature?

Ans.   Ice at 273 K will absorb heat energy or latent heat from the medium to overcome the fusion to become water. Hence the cooling effect of ice is more than the water at same temperature because water does not absorb this extra heat from the medium.

Q8.  What produces more severe burns, boiling water or steam?

Ans.   Steam at 100 °C will produce more severe burns as extra heat is hidden in it called latent heat whereas the boiling water does not have this hidden heat.

Q9.  Name A, B, C, D, E and F in the following diagram showing change in its state

Ans.   A → Liquefication/melting/fusion

              B → Vapourisation/evaporation

              C → Condensation

              D → Solidification

              E → Sublimation

              F → Sublimation

1.  CO2 can be easily liquified and even solidified because

      (a)   It has weak forces of attraction

      (b)   It has comparatively more force of attraction than other gases

      (c)   It has more intermolecular space

      (d)   It is present in atmosphere.

2.  Which of the following has heighest kinetic energy?

      (a)   Particles of ice at 0 °C

(b)   Particles of water at 0 °C

      (c)   Particles of water at 100 °C

(d) Particles of steam at 100 °C

3.  Bose-Einstein Condensate have

      (a)   Very low kinetic energy

(b)   Low kinetic energy

      (c)   High kinetic energy

(d)   Highest kinetic energy.

4.  Which of the following is most suitable for summer?

      (a)   Cotton

(b)   Nylon

(c)   Polyester

(d)   Silk.

5.  Which of the following is incorrect about plasma?

      (a)   Fluorescent tube and neon sign bulbs consist of plasma.

      (b)   The gas gets ionised when electrical energy flows through it.

      (c)   It consists of super-energetic and super-excited particles.

      (d)   The plasma glows with colour which does not depend upon nature of gas.

6.  The colour of vapours formed on sublimation of iodine solid is

      (a)   Purple (violet)

      (b)   Colourless

      (c)   Yellow

      (d)   Orange

7.  Under which of the following conditions we can boil water at room temperature?

      (a)   At low pressure

(b)   At high pressure

      (c)   At very high pressure

(d)   At atmospheric pressure

8.  Which of the following is not endothermic process?

      (a)   Fusion

(b)   Vapourisation

      (c)   Temperature

(d)   Insoluble heavy impurities

9.  Which of the following does not affect rate of evaporation?

      (a)   Wind speed

(b)   Surface area

      (c)   Temperature

(d)   Insoluble heavy impurities

10.  Kinetic energy of molecules is directly proportional to

         (a)   Temperature

(b)   Pressure

         (c)   Both (a) and (b)

(d)   Atmospheric pressure

1. (b)	2. (d)	3. (a)	4. (a)
5. (d)	6. (a)	7. (a)	8. (c)
9. (d)	10. (a)

HIGHER ORDER THINKING QUESTIONS
Matter in Our Surroundings

1.  Which of the following is heaviest metal?

      Pb, As, Al, Ni

2.  Which of the following has highest melting point?

      Ni, Fe, Pt, W.

3.  Which property of cotton makes it suitable for use as clothing in summer?

4.  Name the synthetic fibre which resembles wool in its properties.

5.  Which material is used for making CDs?

6.  Why is rayon called artificial silk?

7.  What is used for coating non-stick kitchen wares?

8.  Which gas is used as referigerant in fridge and in air conditioner?

9.  Why do gold, silver and platinum occur in free state?

Answers.

1.  Pb

2.  W

3.  It absorbs moisture

4.  Acrylic

5.  Polycarbonate

6.  It is prepared from cotton but has shine like silk

7.  Teflon

8.  Freon

9.  Freon

Class IX Science
Sample Paper for Matter in Our Surroundings

1.  Why do we see water droplets collected on the outer surface of a glass container, containing ice?

2.  Explain why solids have fixed shape but liquids and gases do not have fixed shape.

3.  Why is it advisable to use pressure cooker at higher altitudes?

4.  What are fluids?

5.  Why is water liquid at room temperature?

6.  Cotton is solid but it floats on water. Why?

7.  Why are solids generally denser than liquids and gases?

8.  Name the factors that affect evaporation.

9.  How is the high compressibility property of gas useful to us?

10.  With the help of an example, explain how diffusion of gases in water is essential?

11.  On a hot sunny day, why do people sprinkle water on the roof or open ground?

12.  Why to people perspire a lot on a hot humid day?

13.  A balloon when kept in sun, bursts after some time. Why?

14.  Pressure and temperature determine the state of a substance. Explain this in detail.

15.  Explain giving examples the various factors on which rate of evaporation depends.

Class 9th – Science Test 1
Lesson 1- Matter in our surroundings

Time- 60 Minutes

MM- 30

1.  Camphor disappears without leaving any residue. Explain?                                                                                      (2)

2.  Why do we feel cool when we touch a piece of ice?                                                                                                        (2)

3.  What is Latent Heat of Fusion?                                                                                                                                                (2.5)

4.  Define latent heat of Vaporization?                                                                                                                                        (2.5)

5.  How can you show that evaporation causes cooling?                                                                                                       (3)

6.  How can you justify that table is a solid?                                                                                                                             (3)

7.  Arrange the following in decreasing order of force of attraction: Water, Salt, Oxygen, and give reasons.             (3)

8.  What are the characteristics of matter?                                                                                                                                             (3)

9.  The smell of hot sizzling food reaches you several meters away, but to smell the cold food you have to go close. Why?                    (3)

10.  After rains, the rain drops dry away easily- on a sunny day or on a cloudy day? Give reasons.                    (3)

11.  How can matter change its state?                                                                                                                                                        (3)