CBSE Important Questions Class 9 Science Chapter 1: Here are the matter in our surroundings class 9 important questions with answers for Chapter 1 Matter in Our Surroundings.
Practicing these questions will help reinforce your understanding of key concepts such as the states of matter, their properties and the differences between physical and chemical changes. Solving these questions enhances problem-solving skills and prepares you for exams.
Moreover, they provide a solid foundation for more advanced topics in science. If you are looking for class 9 science chapter 1 important questions or need extra practice, make sure to review and practice regularly for the best results. This will help you master matter in our surroundings important questions for CBSE exams.
CBSE Important Questions Class 9 Science Chapter 1 Overview
These questions for Class 9 Science Chapter 1 Matter in Our Surroundings focusing on these important questions of matter in our surroundings class 9, learners can strengthen their foundational knowledge and enhance their exam preparation, ultimately improving their grasp of scientific principles. Regular review of these matter in our surroundings class 9 important questions ensures thorough understanding and better results.
CBSE Important Questions Class 9 Science Chapter 1 Matter in Our Surroundings
Here we have provided CBSE Important Questions Class 9 Science Chapter 1 Matter in Our Surroundings-Multiple Choice Question (1 Mark)
1. Which of the following phenomena takes place when we add a drop of Dettol into the water?
(A) Osmosis (B) Diffusion (C) Sublimation (D) None of the above
Ans: (B) Diffusion
2. Based on the figure given below the rate of evaporation would be maximum in?
(A) Beaker A (B) Beaker B (C) Beaker C (D) Beaker D
Ans: (C) Beaker C
3. A thermometer was put inside a beaker filled with ice at 0°C. The beaker is heated slowly. The temperature does not rise for some time. It is because:
(A) Ice is very cold. (B) Heat was used in changing ice at 0°C to water at 0°C. (C) The density of water is more than the ice. (D) The density of water is less than the ice.
Ans: (B) Heat was used in changing ice at 0°C to water at 0°C.
4. Which one of the following sets of phenomena 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.
Ans: (C) Evaporation, diffusion, expansion of gases.
5. Choose the correct statement of the following.
(A) The conversion of solid into vapours without passing through the liquid state is called vapourisation.
(B) The conversion of solid into vapours without passing through the liquid state is called sublimation.
(C) The conversion of vapours into solid without passing through the liquid state is called freezing.
(D) The conversion of solid into liquid is called sublimation.
Ans: (B) The conversion of solid into vapours without passing through the liquid state is called sublimation.
6. At higher altitudes
(A) The boiling point of a liquid increases.
(B) The melting point of a substance increases.
(C) The boiling point of a liquid decreases.
(D) None of these
Ans: (C) The boiling point of a liquid decreases.
7. Which of the following is matter? Chair, air, love, hate, almonds, thought, cold, cold drink.
Ans: Chair, air, almonds and cold drink are matter.
Short Extra Questions for Class 9 Science Chapter 1
8. Convert the following temperature to a Celsius scale:
(i) 300 K, (ii) 573 K
Ans:
(i) K = 273 + °C:
°C = K – 273
= 300 – 273
= 27°C
(ii) K = 273 + °C:
°C = K – 273
°C = 573 – 273
= 300°C
9. What is the physical state of water at:
(i) 250°C, (ii) 100°C
Ans:
(i) The boiling point of water is 100° C, hence the physical state of water at 250° C will be gaseous.
(ii) The boiling point of water is 100 °C, hence at 100 °C water is exist in both liquid and gaseous state.
10. Why does the temperature remain constant during the state change for any substance?
Ans: The temperature remains constant during the state change for any substance because, during the state change, all of the heat or energy provided to particles of matter is utilized to take the particles of matter apart from each other.
11. Suggest a condition to liquify atmospheric gases.
Ans: Atmospheric gases can be liquified at low temperature and high pressure.
12. Arrange the following substances in increasing order of forces of attraction between the particles – water, sugar, and oxygen.
Ans: The increasing order of forces of attraction between the particles is as follows: Oxygen < Water < Sugar.
13. Give reasons for the following observation: The smell of hot sizzling food reaches you several meters away, but to get the smell of cold food you have to go close.
Ans: The smell of hot sizzling food reaches you several meters away, but to get the smell of cold food you have to go close because hot sizzling food particles have high kinetic energy, which allows them to diffuse quickly in the air and travel a distance of several meters, In contrast, cold food particles have low kinetic energy, thus, they cannot travel and you have to go close to get the smell.
14. The mass per unit volume of a substance is called density. (density = mass/volume). Arrange the following in order of increasing density – air, exhaust from chimneys, honey, water, chalk, cotton, and iron.
Ans: The correct order of increasing densities of the substances is as follows: Air < exhaust from chimneys < cotton < water < honey < chalk < iron.
15. Liquids generally have a lower density as compared to solids. But ice floats on water. Why?
Ans: Ice despite being a solid floats on water because it has a greater amount of space between its molecules compared to water molecules. As a result, the volume of ice is larger than that of water, leading to a lower density of ice. Thus, ice floats on water.
16. Why does a desert cooler cool better on a hot dry day?
Ans: A desert cooler cools better on a hot dry day because on a hot dry day temperature is high and humidity is less which helps in better evaporation. Due to the higher rate of evaporation, it gives a better cooling effect.
17. How does water kept in an earthen pot (matka) become cool during summer?
Ans: The water kept in an earthen pot remains cool in summer because of evaporation. An earthen pot has a large number of tiny pores on its walls and water molecules continuously keeps seeping through these pores to outside the pot. The water evaporates from the pot's surface, and it absorbs heat from the surrounding environment, cooling down the water inside.
18. Why does our palm feel cool when we put some acetone, petrol, or perfume on it?
Ans: Our palm feels cool when we put some acetone or petrol or perfume on them because it evaporate quickly by absorbing heat from our skin and the surrounding air. This rapid evaporation creates a cooling sensation, making our palms feel cool.
19. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Ans: We can sip tea or milk fastly from a saucer because it has a larger surface area than the cup. In larger surface area rate of evaporation is more due to which tea or milk cools rapidly.
20. What type of clothes should we wear in summer?
Ans: We should wear cotton clothes and light-coloured clothes in summer. Cotton is a good absorber of water. Since we sweat a lot in summer, cotton clothes absorb sweat from our bodies and expose the sweat to the atmosphere, making its evaporation faster.
21. Convert the following temperatures to the Kelvin scale:
(i) 25°C, (ii) 373°C
Ans: (i) K = °C + 273
= 25 + 273
= 298 K
(ii) K = °C + 273
= 373 + 273
= 646 K
22. Give a reason for the following observations.
(i) Naphthalene balls disappear with time without leaving any solid.
(ii) We can get the smell of perfume sitting several meters away.
Ans:
(i) Naphthalene balls disappear with time without leaving any solid because they undergo sublimation i.e., they directly change into vapour without passing through the liquid state.
(ii) We can get the smell of perfume sitting several meters away due to diffusion. The perfumes contain volatile solvent which carries pleasant smelling vapour. They fastly from a high concentration area to a low concentration area there by reaching us even several metres away.
23. Give two reasons to justify:
(i) Water at room temperature is a liquid.
(ii) An iron almirah is a solid at room temperature.
Ans:
(i) Water at room temperature around 25 degree celsius liquid because the boiling point of water is 100 degree celsius and the freezing point of water is O degree celsius. Thus, it can not exist as gas or solid at room temperature and exist as liquid further it has fixed volume but no shape and possess fluidity.
(ii) An ion almirah is solid at room temperature because the melting point of iron is very high. Therefore, it in solid at room temperature. Further it also satisfies the characteristics of solid, i.e. it has fixed shape & volume.
24. 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. Hence, the cooling effect of ice would be greater than the water at the same temperature because water does not absorb this extra heat from the surrounding.
25. What produces more severe burns, boiling water or steam?
Ans: Water vapour at 373K has more energy than water at 373K as the steam has absorbed the latent heat of vaporization to change the state. Therefore, steam produces more severe burns than boiling water.
26. What is evaporation and which factors affect it?
Ans: Evaporation can be defined as the process of conversion of a substance from its liquid state to a gaseous state at any temperature below its boiling point.
Factors affecting evaporation:
(i) Surface area
(ii) Temperature
(iii) Humidity
(iv) Wind speed
27. What happens when we apply pressure to the particles of matter?
Ans: Pressure can be defined as the force applied per cross-sectional area. Therefore when we apply pressure to the particles of matter, particles of matter will come nearer to each other and their kinetic energy additionally decreases.
28. Define latent heat of vaporization and latent heat of fusion.
Ans: Latent heat of fusion is the amount of heat energy absorbed at Atmosphere pressure at its melting point without any change in temperature by the unit mass of a solid to convert into a liquid phase. Latent heat of vaporization is the amount of heat energy absorbed at its boiling point without any change in temperature, by the unit mass of a liquid to transform into a gaseous phase.
29. If the melting point of object A is high, what state do you expect it to be at room temperature?
Ans: The temperature at which a substance changes its state from solid to liquid is called its melting point. At a temperature below melting point, the substance will be in the solid state. Therefore, if the melting point of object A is high then the object will be in the solid state.
30. What happens when the temperature of the solids increases?
Ans: When the temperature of a solid increases the kinetic energy also increases. The particles inside start moving with a great speed and the solid gets converted into liquid.
31. What happens when heat is supplied to a solid?
Ans: When heat is supplied to solid, the kinetic energy of the particle increases. The particle overcome the force of attraction and start morning freely. Thus, change the state from solid to liquid.
32. What is the effect of wind speed on evaporation?
Ans: When wind speed increases, it blows away the water vapour present in the air. Due to a decrease in water vapour content air humidity of air decreases. So, due to a decrease in the humidity of the air, the rate of evaporation increases.
33. Why is evaporation a surface phenomenon?
Ans: Evaporation is a surface phenomenon because only the surface particles of the liquid absorb energy and get converted into vapours, therefore evaporation is called a surface phenomenon.
34. Water boils at 102°C; is it pure? Will it freeze at 0°C?
Ans: No, the water is not pure. It is because the boiling point of pure water is 100°C but the given sample boils at 102°C. It indicates that it has some dissolved impurities. No, the water will not freeze at 0°C. Instead, it will freeze below 0°C as it has impurities dissolved in it.
35. A diver can cut through water in a swimming pool. Which property does this show?
Ans: A diver can cut through water in a swimming pool. The properties of matter observed are that matter has spaces between them and the intermolecular forces of attraction between liquid particles are not very strong.
36. What are the characteristics of the particles of matter?
Ans: The particles of matter have the following
characteristics:
i. The particles of matter are in continuous
motion.
ii. There are gaps between the particles of
matter.
iii. There is a force of attraction between the
particles of matter which keeps them together.
(Long Answer Type Questions)
37. (a) Tabulate the differences in the characteristics of states of matter.
(b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Sol (a).
(b).
• Rigidity: It is the property of matter to maintain its shape even if external forces work. Solids show rigidity.
• Compressibility: It is the property of matter to allow compression under high pressure Gases show compressibility.
• Fluidity: It is the property of a substance to easily flow and allow change in its shape under external forces Liquids and gases shows Fluidity.
• Filling a gas container: Gases can be compressed easily hence they can be filled within a vessel at high pressure. This property of gases allows their convenient filling into a small container or cylinder and that also in a large volume.
• Shape: Solids have definite shape while Liquids acquire the shape of their container and gases don't have any shape.
• Kinetic energy: It is the of energy present in an object when it is under motion. As the particles of that matter are continuously moving therefore matter has kinetic energy. However Greater is the movement more will be the kinetic energy and vice a versa i.e. solid < liquid < gas. Solid have maximum density followed by liquids and gases (Density → Mass per unit volume of a substance/matter is known as its density i.e. density = mass/volume).
38. Give reasons:
(a) A gas fills completely the vessel in which it is kept.
(b) A gas exerts pressure on the walls of the container.
(c) A wooden table should be called a solid.
(d) We can easily move our hand in the air but to do the same through a solid block of wood we need a karate expert.
Sol. (a) The particles of gases have less force of attraction between them. The particles are free to move, so they will fill the vessel in which it is kept.
(b) The particles of gas have a weak force of attraction. So, they are constantly moving randomly. The pressure exerted by a gas is due to the random motion of particles in the gas. These particles collide with the walls of the container. These collisions apply force and hence gas exerts pressure on the wall of container.
(c) The wooden table has a definite shape and a definite volume. The particles of wood are closely packed. They do not take the shape of any container. They are rigid in nature. Hence wooden table satisfies the properties of a solid.
(d) The particles of air are very loosely bounded. They are far away from each other having a lot of space between them. Hence, we can easily move our hands in the air. But in a solid block, the particles have no space and are tightly held by a strong force of attraction.
39. Name A, B, C, D, E and F in the following diagram showing changes in its state.
A is fusion
B is Vapourisation.
C is Condensation.
D is Freezing/Solidification.
E is sublimation.
F is Deposition.