NCERT Exemplar Solution Class 9 Science Chapter 1
NCERT Exemplar Solution Class 9 Science Chapter 1 Matter In Our Surroundings all Questions Answer Solution. NCERT Exemplar Class 9 Science Chapter 1 Solution PDF.
NCERT Exemplar Solution Class 9 Science Chapter 1: Overview
NCERT Exemplar Solution Class 9 Science Chapter 1 |
|
Board | NCERT |
Topic | Exemplar Problem Solution |
Class | 9 |
Subject | Science |
Chapter | 1 |
Chapter Name | Matter In Our Surroundings |
NCERT Exemplar Solution Class 9 Science Chapter 1 Matter In Our Surroundings
1) Which one of the following sets of phenomenon would increase on raising the temperature?
a) Diffusion, evaporation, compression of gases
b) Evaporation, compression of gases, solubility
c) Evaporation, diffusion, expansion of gases
d) Evaporation, solubility, diffusion, compression of gases.
Answer:- c) Evaporation, diffusion, expansion of gases
Evaporation, diffusion and expansion of gases all the three phenomenon increases with increased temperature. While the other sets containing some other Phenomenon does not increase with rise in temperature.
Evaporation is dependent over the temperature to change from solid to liquid as temperature increases the rate of evaporation increase.
Diffusion occurs when particles of matter intermix with each other these happens for to increase in temperature.
Expansion of gases contains moving of molecules. These moves faster on increasing the temperature.
2) Seemavisited a Natural Gas Compressing Unit and found that the gas can be liquefied under specific conditions of temperature and pressure. While sharing her experience with friends she got confused. Help her to identify the correct set of conditions
a) Low temperature, low pressure
b) High temperature, low pressure
c) Low temperature, high pressure
d) High temperature, high pressure
Answer:- c) Low temperature, high pressure
Low temperature and high pressure is needed to compress the gas and to convert it into liquid. Gas particles has lots of spaces between them. When pressure is applied over it the particles gets closer and form the liquid. During these process lots of heat is produced which is need to cool down. These cooling lowers the temperature and help to liquefy it.
3) The property to flow is unique to fluids. Which one of the following statements is correct?
a) Only gases behave like fluids
b) Gases and solids behave like fluids
c) Gases and liquids behave like fluids
d) Only liquids are fluids
Answer:- c) Gases and liquids behave like fluids.
The gaps between the molecules of liquid and gaseous is large as compared to solid. The less intermolecular force of attraction between the particles in liquid and solid is responsible for the flow of gaseous and liquids and it behaves like fluids.
4) During summer, water kept in an earthen pot becomes cool because of the phenomenon of
a) Diffusion
b) Transpiration
c) Osmosis
d) Evaporation
Answer:- d) Evaporation
In the summer season temperature is high and due to these the water is evaporated through the pores of the earthen pot which reduces the temperature of the pot and cools down the water after some time.
Transpiration occurs in plants.
Osmosis and diffusion does not occur in the earthen pot. As it contains the movement of particles from one concentration to another.
5) A few substances are arranged in the increasing order of ‘forces of attraction’ between their particles . Which one of the following represents a correct arrangement?
a) Water , air, wind
b) Air, sugar, oil
c) Oxygen, water , sugar
d) Salt, juice, air
Answer:- c) Oxygen, water , sugar
Oxygen is a gas which has very less intermolecular force of attraction between their molecules.
Water is an liquid and it has less intermolecular force attraction between their molecules but higher than gaseous.
Sugar is a Solid which has the highest intermolecular force of attraction than the liquid and gaseous.
Therefore the correct increasing order of the intermolecular force of attraction is oxygen, water and sugar.
6) On converting 25°C, 38°C and 66°C to Kelvin scale, the correct sequence of temperature will be
a) 298 k, 311 K and 339 K
b) 298 K , 300 K and 338 K
c) 273 K, 278 K, and 543 K
d) 298 K, 320 K, and 338 K
Answer:- a) 298 k, 311k, and 339 k
For converting the given temperature into kelvin we have to add 273 to each temperature and we get the answer 298k, 311 k, and 339 k respectively.
7) Choose the correct statement of the following
a) Conversion of solid into vapours without Passing through the liquid state is called sublimation.
b) Conversion of vapours into solid without Passing through the liquid state is called vaporisation.
c) Conversion of vapours into solid without Passing through the liquid state is called freezing.
d) Conversion of solid into liquid is called sublimation.
Answer:- a) conversion of solid into vapours without Passing through the liquid state is called sublimation.
Vaporisation is the process which liquid gets converted into gaseous.
Freezing is the conversion of liquid into solid at its freezing point.
Sublimation is the process in which solid is directly converted into vapours without going through liquid state.
8) The boiling points of diethyl ether, acetone, and n-butyl alcohol are 35°C, 56° C and 118°C respectively. Which one of the following correctly represents their boiling points in Kelvin scale ?
a) 306 K, 329 K , 391 K
b) 308 K, 329 K, 392 K
c) 308 K, 329 K, 391 K
d) 329 K, 392 K, 308 K
Answer:- c) 308 K, 329 K, 391 K
For getting the boiling temperature into Celsius we have to add 273 in each given temperature. Then we will get the answer boiling points 308 k, 329 k and 391 k of diethyl ether, acetone and n-butyl alcohol respectively.
9) Which condition out of the following will increase the evaporation of water?
a) Increase in temperature of water
b) Decrease in temperature of water
c) Less exposed surface area of water
d) Adding common salt to water
Answer:- a) Increase in temperature of water
Phenomenon of Evaporation is dependent over the surface, temperature and humidity. High temperature increases the rate of evaporation. It increases the kinetic energy and gives it more energy for conversion of liquid into gaseous state. Therefore increase in temperature increases the rate of evaporation.
10) In which of the following conditions, the distance between the molecules of hydrogen gas would increase?
I) Increasing pressure on hydrogen containing in a closed container
II) Some hydrogen gas leaking out of the container
III) Increasing the volume of the container of hydrogen gas
IV) Adding more hydrogen gas to the container without increasing the volume of the container
a) I) and III)
b) I) and IV)
c) II) and III)
d) II) and IV)
Answer:- c) II) and III)
The distance between the molecules of hydrogen gas will increase when there will be less quantity of hydrogen gas therefore the gas in the container should be leak out. Or another method will be increasing the volume of container to get the enough space for the gas.
Short Answer Questions
11) A sample of water under study was found to boil at 102°C at Normal temperature and pressure. Is the water pure? Will this water freeze at 0°C ? Comment.
Answer:- The boiling point of water is 100°C but here these sample of water is boiling at102°C. These is because the water sample contains some amount of impurities in it, therefore the water is not pure water, and thus it will not freeze at 0°C. It will freeze below 0°C.
12) A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following (fig. 1.1) would correctly represent the result? Justify your choice.
Answer:-
The correct answer is figure D. Because when water and ice is heated together it does not directly raise the temperature, the temperature of the mixture is primarily at equilibrium i.e. zero, the mixture when started heating it first used up its latent heat to melt the ice into water. Therefore the temperature did not rise at first and when the ice converted into the water then temperature stated rising.
13) Fill in the blanks :
a) Evaporation of a liquid at room temperature leads to a ___________ effect.
Answer:- Evaporation of a liquid at room temperature leads to a cooling effect.
b) At room temperature the forces of attraction between the particles of solid substances are _________ than those which exist in the gaseous state.
Answer:- At room temperature the forces of attraction between the particles of solid substances are stronger than those which exist in the gaseous state.
c) The arrangement of particles is less ordered in the _________ state. However, there is no order in the ___________ state.
Answer:- The arrangement of particles is less ordered in the liquid state. However, there is no order in the gaseous state.
d) ________ is the change of solid state directly to vapour state without going through the ________ state.
Answer:- sublimation is the change of solid state directly to vapour state without going through the liquid state.
e) The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called __________.
Answer:- The phenomenon of change of a liquid into the gaseous state at any temperature below it’s boiling point is called evaporation.
14) Match the physical quantities given in Column A to their SI units given in Column B:
A B
a) Pressure i) cubic metre
b) Temperature ii) kilogram
c) Density iii) Pascal
d) Mass iv) Kelvin
e) Volume v) kilogram per Cubic metre
Answer:-
a) Pressure →iii) pascal
b) Temperature → iv)kelvin
c) Density →v) kilogram per cubic metre
d) Mass→ii) kilogram
e) Volume →i) cubic metre
15) The non SI and SI units of some physical quantities are given in Column A and Column B respectively. Match the units belonging to the same physical quantity.
(A) (B)
a) Degree Celsius i) kilogram
b) Centimetre ii) pascal
c) Gram per centimetre iii) metre cube
d) Bar iv) kelvin
e) Milligram v) kilogram Per Metrec ube
Answer:-
a) Degree Celsius → iv) kelvin
b) Centimetre → iii)metre
c) Gram per Centimetre cube → v) kilogram per Metre cube
d) Bar → ii)pascal
e) Milligram → i) kilogram
16) ‘Osmosis is a special kind of diffusion.’ Comment.
Answer:-
The movement of through a semi permeable membrane from the lower concentrations to the higher concentrations is known as “Osmosis”. While the diffusion is known as the movement of particles in liquid and gases from the lower concentration to the higher concentration. The movement in osmosis is performed as the diffusion. Thus it is a special kind of diffusion.
17) Classify the following into Osmosis / diffusion.
a) Swelling up of a raisin on keeping in water.
Answer:- it is an Osmosis
b) Spreading of virus on sneezing.
Answer:- it is an Diffusion
c) Earthworm dying on coming in contact with common salt.
Answer:- it is an Osmosis.
d) Shrinking of grapes kept in thick sugar syrup.
Answer:- It is an Osmosis
e) Preserving pickles in salt.
Answer:- it is an Osmosis
f) Spreading of smell of cake being baked through out the house.
Answer:- it is an Diffusion.
g) Aquatic animals using oxygen dissolved in water during Respiration.
Answer:- it is an Osmosis.
18) Water as ice has cooling effect, whereas water as steam may cause severe burns. Explain these observations.
Answer:- Ice which is the solid form of water has very less energy therefore the water molecules in the ice form absorb the energy from our body and thus gives us a cooling effect. on the other side, steam which is the gaseous form of hot water, has the highest amount of energy therefore steam transfers these high energy or heat to our body and thus causes us burns.
19) Alka was making tea in a kettle, suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.
Answer:-
The water boiling in the kettle and the steam both has the same temperature. The energy of the stream is Highest, because it is in the form of latent heat of vaporisation. The boiling water molecules does not have that level of energy. Thus we can found that steam is hot than the boiling water in the kettle.
20) A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator ( temperature < 0°C) . If you could measure the temperature of the content of the tumbler, which of the following graphs ( fig 1.2) would correctly represent the change in its temperature as a function of time.
Answer:-The correct answer is the figure (a), When a tumbler of hot water is kept in refrigeratorthe temperature of water will not directly fall down, firstly it will come upon the 0°c i.e. freezing point. Then at these stage the water will be converted into ice, maintaining the 0°c temperature for sometime, and then further the temperature will decrease down again.
22) Look at fig. 1.3 and suggest in which of the vessels A,B,C or D the rate of evaporation will be the highest? Explain.
Answer:-
The evaporation rate will be Highest in the figure C. Rate of Evaporation of water will be highest with large surface area. it is also depends upon the speed of air, the highest speed of air will move away maximum water vapour particles with it. And thus the rate of evaporation will be increased. In figure C, both are available the large surface area and also the high speed of air due to fan above it. Therefore the rate of evaporation will be highest in the figure C.
22) A) conversation of solid to vapour is called sublimation. Name the term used to denote the conversion of vapour to solid.
Answer:-
The conversion of Solid state to vapour without going through liquid state is known as Sublimation.
The conversion of vapours directly into the Solid without undergoing through the liquid state is known as Deposition.
B) Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion?
Answer:-
The conversion of solid to liquid state is called Fusion.
At one atmospheric pressure the amount of heat energy required for changing the 1 kg of solid into its liquid form at the melting point is known as latent heat of fusion.
Long Answer Questions
23) You are provided with a mixture of naphthalene and Ammonium chloride by your teacher. Suggest an activity to separate them with well labelled diagram.
Answer:- The provided mixture is of naphthalene and ammonium chloride. Naphthalene is Non-polar in nature i.e. it is insoluble in water, but it is soluble in ether which is an organic solvent. On the other side ammonium chloride is polar i.e soluble in water. Ammonium is also volatile on high temperature. Ammonium chloride on heating will decomposed to dryness.
Thus these mixture can be separated with three steps-
- Decantation
- Filtration
- Evaporation
A. Decantation
Naphthalene and Ammonium chloride mixture can be separated, first step is decantation.Naphthalene being non- polar will not dissolve in water and remain on the upper layer of water. While the Ammonium chloride will dissolve in water and settle down to the bottom of the flask.
B. Filtration
Further these mixture is filtrated with the funnel having a filter paper in it. Naphthalene remains over the funnel on filter paper. And the filtrate containing ammonium chloride taken out in the test tube.
C. Evaporation
The filtrate out ammonium chloride will be separated by the evaporation process. Taking out the filtrate into a container and let it keep in slightly high temperature. The water will evaporate and the ammonium chloride will remain in the container in the dry form.
24) It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon clothes respectively. Who do you think would be more comfortable and why?
Answer:-
Cotton is the natural fibre and nylon is synthetic fibre. Cotton is a good absorber of water. Thus Cotton can better absorb the sweat due to heat in summer days. These absorption leads to evaporation and gives the cooling effect to the body. Whereas nylon cannot absorb so as cotton. Therefore Priyanshi will feel more comfortable wearing cotton cloths in summer days.
25) You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. What steps would you take to dry it faster?
Answer:- We can take following steps to dry the wet cotton shirt fast-
1) We can wave the shirt speedily under the full speed fan or under the sun so that high speed of air or temperature of sun will evaporate the water fast.
2) We can use the dryer over the wet shirt, the increased temperature will evaporate the water fast and thus the shirt will dry faster.
3) Spreading the shirt over the hot surface so that increasing the surface area of the shirt will help in the evaporating the water fast.
26) Comment on the following statements:
a) Evaporation produces cooling.
Answer:-
Evaporation is Dependent over the surface area. The particles of the water takes energy form the surface and thus the particles overcome the force of attraction which is present in the liquid. And it turns into the vapour state. These process produces cooling because it takes energy from surface and thus it gets cool.
b) Rate of evaporation of an aqueous solution decreases with increase in humidity.
Answer:-
Phenomenon of Evaporation is dependent over the surface area. But it is also depends upon the temperature, speed of wind and humidity. These factors impact over the rate of evaporation. Evaporation needs temperature as the particles gain energy and transferred from liquid to gaseous state, but in humid atmosphere temperature is less also it has some water droplets or Fog in the air these reduces the amount of energy need by the aqueous solution to convert into gaseous.
c) Sponge though compressible is a solid.
Answer:-
Sponge is compressible because it has very small pores which is always filled with air. But when we put pressure on it or compress it that time the air comes out. But though it is an Solid because it possesses a proper definite shape and these shape does not change till you put pressure on it.
27) Why does the temperature of a substance remain constant during its melting point or boiling point ?
Answer:- Latent heat of fusion is the amount of energy required for changing the solid state of matter into its liquid state at its melting point , also latent heat is also responsible for he Conversion of liquid into gaseous, at its boiling point. These latent heat of fusion provide the required amount of energy for the breaking of bonds between them andchanges from solid to liquid or liquid to gaseous state. When the substances get the threshold energy it transfer from solid to liquid and liquid to gaseous and Thus temperature of substances remains constant at it boiling and melting point upto threshold energy.