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Science Answer the questions.[Che-2M]

Matter in Our Surroundings · CBSE STD 9 (CBSE - English Medium). 90 questions.

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Question 12 Marks
Would you cool a bucket of water more quickly by placing it on ice or by placing ice in it? Give reasons for your answer.
Answer
We would place ice in the water to cool it more quickly because the ice takes its latent heat from the water and hence cools it more effectively. On the other hand, if we keep the water on ice then the latent heat would be taken from the surrounding air hence releasing its coolness to the surrounding and not the water.
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Question 22 Marks
Why is the density of solids mostly higher than that of liquids?
Answer
However, the volume of liquids is larger than volume of solids. This is because of expanding movement of a fluid of liquids that solid does not possess. The liquids always have lower density because they have larger volume, but yet the same mass.
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Question 32 Marks
Why is ice at 273K more effective in cooling than water at the same temperature?
Answer
Ice at 273K is less energetic than water. It is because of the difference in the latent heat of fusion which is present in water at the same temperature in the form of extra energy.
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Question 42 Marks
Why is a liquid (the hydraulic fluid) used to operate the brakes in a car?
Answer
A liquid is always used to operate the brakes in a car. This is because the particles in brake oil can move freely without being compressed much and thus can transmit the applied force into pressure, which is applied on the brakes efficiently.
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Question 52 Marks
Why gases are compressible but not liquids?
Answer
The inter molecular space in between the constituent particles is maximum in gases, little less in the liquids and the least in solids. On applying pressure, the gaseous particles come together, where as in liquids and solids, the particles are very close and hence cannot be further brought closer.
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Question 62 Marks
Why do people in villages use earthen pots in summer to cool water?
Answer
There are some pores in an earthen pot through which the liquid inside the pot evaporates. This evaporation makes the water inside the pot cool. In this way, water kept in an earthen pot becomes cool during summers.
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Question 72 Marks
Why do gases have neither a fixed shape nor a fixed volume?
Answer
A gas does not have a fixed shape or fixed volume because the particles of gases do not have fixed positions or fixed spaces between them.
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Question 82 Marks
Why does water have higher boiling point than alcohol? At what temperature in Kelvin, it can be changed into solid state and into vapours?
Answer
Water has higher boiling point than alcohol because the extent of hydrogen bonding is stronger in water than in alcohol. Moreover we know that water freezes into ice at 273k and changes into vapour states at 373k.
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Question 92 Marks
Why does the temperature remain constant during the change in the state for a substance?
Answer
Temperature of any substance remains constant because the heat supplied to increase the temperature is utilised in changing the state of matter. this is because of latent heat. Since the heat is used to overcome the force of attraction, the temperature of the substance does not change.
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Question 102 Marks
Why does the temperature of a substance remain constant during the change of state?
Answer
The temperature of a substance remains constant during the change of state because the heat gets used up in changing the state by overcoming the forces of attraction between the particles.
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Question 112 Marks
Why does steam cause more severe burns than boiling water?
Answer
Steam causes more severe burns than boiling water because the steam contains more heat, in the form of latent heat, than boiling water. Hence, when steam falls on our skin and condenses to produce water, it gives out 22.5 × 105 Joules per kilogram more heat than boiling water.
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Question 122 Marks
Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Answer
Acetone, petrol or perfume evaporate when they come into contact with air. The evaporation causes cooling sensation in our hands.
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Question 132 Marks
Why does evaporation cool a liquid?
Answer
Evaporation causes cooling because when a liquid evaporates, it draws or takes the latent heat of vaporisation from ‘anything’ which it touches and hence the substances or surroundings lose heat and get cooled.
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Question 142 Marks
Why does all the water of the earth not get evaporated during hot summer days?
Answer
All water on earth does not get evaporated on hot summer days because of the high value of latent heat of vaporization of water.
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Question 152 Marks
Why does a gas fill a vessel completely?
Answer
The particles of a gas have high kinetic energy and negligible forces of attraction amongst them. Due to this, the particles of a gas are constantly moving with high speeds in all the directions and the gas completely fills the vessel in which it is kept.
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Question 162 Marks
Why does a gas exert pressure?
Answer
Because of high energy and negligible forces of attraction, the particles of a gas move with high speed in all directions. Thus, the pressure exerted by a gas is due to the constant collisions of the fast moving gas particles against the walls of the container.
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Question 172 Marks
Why are gases so easily compressible whereas it is almost impossible to compress a solid or a liquid?
Answer
Gases can be compressed easily because its particles are far apart and there are large spaces between them (which can be reduced by compression).
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Question 182 Marks
Why a balloon kept in a sun burst after sometime?
Answer
A balloon when kept in sun bursts after some time because outside the temperature is high and due to that the kinetic energy increases and the molecules of gas particles inside exerts a pressure on the walls of the balloon so it will continue to expand and there a stage will come that the balloon will burst.
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Question 192 Marks
Whish of the following diffuses fastest and which the slowest?
Solid, Liquid, Gas
Give reasons for your answer.
Answer
Solids diffuse the slowest as the particles in solids do not move from their fixed positions. Gases diffuse the fastest as the particles in gases move very quickly in all directions.
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Question 202 Marks
Which produces more severe burns: boiling water or steam? Why?
Answer
Steam causes more severe burns than boiling water because the steam contains more heat, in the form of latent heat, than boiling water. Hence, when steam falls on our skin and condenses to produce water it gives out 22.5 × 105 joules per kilogram more heat than boiling water.
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Question 212 Marks
Which contains more heat, 1kg of water at 100°C or 1kg of steam at 100°C? Give reason for your answer.
Answer
1Kg of steam at 100°C has more heat than water at the same temperature because when water changes into steam, it absorbs latent heat, but when steam condenses to form water, an equal amount of latent heat is given out.
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Question 222 Marks
Which contains more heat, 1kg of ice at 0°C or 1kg of water at 0°C? Give reason for your answer.
Answer
The latent heat of fusion of ice is 3.34 × 105J/ Kg. It means that 3.34 × 105 joules of heat is required to change 1Kg of ice at its melting point of 0°C into water at the same temperature (of 0°C). This means that 1Kg of ice at 0°C has 3.34 × 105 joules of less heat than 1kg of water at the same temperature of 0°C.
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Question 232 Marks
When water is heated to a temperature x, it gets converted into steam at temperature x by a process called R. And when steam at temperature x is cooled, it gets reconverted in to water at the same temperature x by a process called S.
  1. How much is the value of x in Kelvin?
  2. What is the process R called?
  3. What is the name of the energy absorbed during the process R?
  4. What is process S known as?
  5. What is the name of energy released during the process S known as?
Answer
  1. The value of ‘x’ in Kelvin is 373K.
  2. Vaporisation or boiling.
  3. Latent heat of vaporisation.
  4. Condensation.
  5. Latent heat of condensation.
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Question 242 Marks
When water is cooled to a temperature x, it gets converted into ice at temperature x by a process called P. And when ice at temperature x is warmed, it gets reconverted into water at the same temperature x in a process called Q.
  1. What is the value of temperature x in Kelvin?
  2. What is the process P known as?
  3. What is the name of energy released during process P?
  4. What is the process Q known as?
  5. What is the name of energy absorbed during process Q?
Answer
  1. 273K.
  2. The name of the process is freezing.
  3. Latent heat of freezing.
  4. Melting.
  5. Latent heat of fusion.
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Question 252 Marks
When ice at -10°C is slowly heated, temperature of ice gradually increases till 0°C, the temperature of the system remains constant when the ice change into water and then further rises. Explain the observation.
Answer
When the ice is at 0 degree Celsius the temperature stops because the temperature is used to change the state of matter. this is also called as latent heat of fusion.
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Question 262 Marks
What is the SI unit of pressure? Give its value in atm unit.
Answer
The unit of pressure in the SI system is the pascal (Pa), defined as a force of one Newton per square meter. The conversion between atm, Pa, and torr is as follows: 1 atm = 101325 Pa = 760 torr.
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Question 272 Marks
What is the major factor which determines the state of matter?
Answer
Following factors determine the states of matter:
  • Kinetic energy.
  • Distance between particles.
  • Force of attraction.
  • Density.
  • Rigidity, etc.
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Question 282 Marks
What is sublimation? Name two substances (other than ammonium chloride) which undergo sublimation.
Answer
The changing of a solid directly into vapours on heating and of vapours into solid on cooling is known as sublimation. The common substances which undergo sublimation are Camphor and Naphthalene.
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Question 292 Marks
What is meant by kinetic energy?
Answer
The kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.
$\text{v}=\frac{1}2{}\text{mv}^2$
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Question 302 Marks
What is meant by ‘diffusion’? Give one example of diffusion in gases.
Answer
The spreading out and mixing of a substance due to the motion of its particles is called diffusion.
For example: Smell of food being cooked in the kitchen reaches us even from a considerable distance.
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Question 312 Marks
What is fluid?
Answer
A fluid is any substance that flows or deforms under applied shear stress. Fluids comprise a subset of the states of matter and include liquids, gases, and plasma.
Examples: All liquids and gases are fluids (air, water, oil)
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Question 322 Marks
What is evaporation? State the various factors which affect evaporation.
Answer
The process of a liquid changing into vapour (or gas) even below its boiling point is called evaporation. The factors affecting rate of evaporation are:
  1. Temperature.
  2. Surface area.
  3. Humidity.
  4. Wind speed.
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Question 342 Marks
What do you think, matter is made up of small particles or not?
Answer
Any substance that occupies the area and has mass is thought as matter. States of matter - Matter exist in 3 completely different states that are Solid, Liquid and Gas. Matter is created from terribly tiny particles.
  • All matter is created from terribly tiny particles that don't seem to be visible to eye.
  • They need areas between them.
  • Particles of matter move perpetually.
  • They’re attracted towards one another.
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Question 352 Marks
What does the diffusion of gases tell us about their particles?
Answer
Diffusion in gases shows that their particles move very quickly in all directions and the rate of diffusion of a gas depends on its density. Light gases diffuse faster than heavy gases.
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Question 362 Marks
What are the characteristics of the particles of matter?
Answer
The characteristics of particles of matter are:
  1. They have intermolecular space between them.
  2. They are continuously moving.
  3. They attract each other.
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Question 372 Marks
What about a rubber band, can it change its shape? Is it solid?
Answer
A rubber band can change its shape on stretching but it is a solid. This happens because pressure is applied on the band which makes it to change the shape and it gains its original shape when released. So, its a solid.
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Question 382 Marks
Temperature of a liquid does not change when it boils. Why?
Answer
When energy is added to a liquid at the boiling temperature, its converts the liquid into a gas at the same temperature. In this case, the energy added to the liquid goes into breaking the bonds between the liquid molecules without causing the temperature to change.
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Question 392 Marks
Suggest a method to liquefy atmospheric gases.
Answer
The gases can be converted into liquids by bringing its particles closer so atmospheric gases can be liquefied either by decreasing temperature or by increasing pressure.
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Question 402 Marks
State two characteristics of matter demonstrated by:
Diffusion.
Answer
Diffusion:
  1. Matter is made up of tiny particles.
  2. The particles of matter are constantly moving.
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Question 412 Marks
State two characteristics of matter demonstrated by:
Brownian motion.
Answer
Brownian motion:
  1. The particles of matter are very, very small.
  2. The particles of matter are constantly moving.
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Question 422 Marks
People sprinkle water on open ground or roof on a hot sunny day. Why?
Answer
The evaporation of water causes a cooling effect because the large latent heat of vaporization of water helps to cool the hot surface. Therefore, On a hot sunny days, people sprinkle water on the roof or the open ground.
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Question 432 Marks
Out of four gases Cl2, CO2, CH4, N2, which gas would diffuse most rapidly and why?
Answer
Out of Cl2, CO2, CH4 and N2 the gas which will diffuse more rapidly is CH4. This is because mass of CH4 is least and diffusion is inversely proportional to mass of gas i.e., lighter gases diffuses faster.
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Question 442 Marks
On a hot humid day, why do people perspire a lot?
Answer
In hot humid days, sweating occurs due to high body temperature, but since the air around our bodies already contains water vapour in high amount (humidity), the sweat does not evaporate and we feel that we are perspiring a lot.
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Question 452 Marks
  1. Compare the properties of solids, liquids and gases in tabular form.
  2. Give two reasons for saying that wood is a solid.


During class, the students resemble molecules in a solid (because they are very close to one another)


While going from one classroom to another the students resemble molecules in a liquid (because they are a little more father apart from one another)

Answer
Solids
Liquids
Gases
i
Solids have a fixed shape and a fixed volume.
Liquids have a fixed volume but no fixed shape.
Gases have neither a fixed volume nor a fixed shape.
ii
Solids cannot be compresses much.
Liquids cannot be compresses much.
Gases can be compressed easily.
iii
Solides have high densities.
Liquids have moderate to high densities.
Gases have very low densities.
iv
Solids do not fill their container completely.
Liquids do not fill their container completely.
Gases fill their container completely.
v
Solids do not flow.
Liquids generally flow easily.
Gases flow easily.
  1. Wood is a rigid object which has a tendency to maintain its shape when subjected to outside force.
  2. It has a definite shape and definite volume.
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Question 462 Marks
Name two gases of air which dissolve in water by diffusion. What is the importance of this process in nature?
Answer
Carbon dioxide and Oxygen gas dissolve in water by diffusion. This process is important as these gases are essential for the survival of aquatic plants and animals. The aquatic plants use the dissolved carbon dioxide for preparing food by photosynthesis and aquatic animals use the dissolved oxygen in water for breathing.
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Question 472 Marks
Name the three states of matter. Give one example of each.
Answer
Three states of matter are:
  1. The solid state: Ice.
  2. The liquid state: Water.
  3. The gas state: Air.
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Question 482 Marks
Name the chemical compound contains in nail-polish remover.
Answer
Acetone is one of the main components in nail polish remover. The formula is C3H6O. Acetone is made up of carbon, hydrogen, and oxygen combined. It is a chemical that is found naturally in the environment and is produced in factories all over.
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Question 492 Marks
How is ammonia gas liquefied?
Answer
Ammonia gas is liquefied by applying high pressure and lowering the temperature of the gas. Lowering the temperature is done by continuously pouring water over the coils carrying the compressed gas.
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Question 502 Marks
How do solids, liquids and gases differ in shape and volume?
Answer

  1. Solids: They have a fixed shape and a fixed volume.

  2. Liquids: They have a fixed volume but no fixed shape.

  3. Gases: They neither have a fixed shape nor a fixed volume.

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