Ncert Solutions for Class 9 Science Chapter 1: Matter in our surroundings question answers
| Textbook | Ncert |
| Class | Class 9 |
| Subject | Science |
| Chapter | Chapter 1 |
| Chapter Name | matter in our surroundings class 9 ncert solutions |
| Category | Ncert Solutions |
| Medium | English |
Are you looking for Class 9 Science Chapter 1 question answer ? Now you can download Matter in our surroundings question answers pdf from here.
In Text Questions Page No: 3
Question 1: Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume.
Answer 1: Matter includes anything that has mass and takes up space. From your list, the following are matter: Chair, air, almonds and lemon water
Question 2: Give reasons for the following observation:
The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.
Answer 2: The smell of hot sizzling food reaches you from several metres away because heat increases the rate of evaporation of volatile substances in the food. These evaporated particles mix with air and diffuse faster, allowing the smell to travel a greater distance. In contrast, cold food has lower evaporation and diffusion rates, so the smell doesn’t spread far—you need to be close to detect it.
Question 3: A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?
Answer 3: A diver is able to cut through water in a swimming pool. This shows that the particles of water have intermolecular space and has less force of attraction.
Question 4: What are the characteristics of the particles of matter?
Answer 4: The characteristics of particles of matter are:
→ Particles of matter have spaces between them.
→ Particles of matter are continuously moving.
→ Particles of matter attract each other.
In Text Questions Page No: 6
Question 1: 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.
Answer 1: Density is depending on mass and volume hence higher the mass higher will be the density and out of these heavier particles have higher mass as compare to lighter one so the order of increasing density of given substances can be written as follows:
Air < Exhaust from chimney < Cotton < Water < Honey < Chalk < Iron.
Question 2: (a) Tabulate the differences in the characterisitcs of states
of matter.
(b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Answer 2: (a) Differences in Characteristics of States of Matter
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Shape | Fixed | Takes shape of container | No fixed shape |
| Volume | Fixed | Fixed | Not fixed (fills container) |
| Compressibility | Negligible | Very low | High |
| Fluidity | Cannot flow | Can flow | Can flow easily |
| Interparticle Space | Very small | Moderate | Large |
| Kinetic Energy | Least | Moderate | Highest |
| Rigidity | High (rigid) | Less rigid | Not rigid |
(b) Comments on the Given Properties
- Rigidity: The tendency of a substance to maintain shape; high in solids, low in liquids and gases.
- Compressibility: Ability to reduce volume under pressure; highest in gases, very low in liquids, negligible in solids.
- Fluidity: Ability to flow; liquids and gases are fluid, solids are not.
- Filling a Gas Container: Gases expand to fill the entire volume of a container due to high kinetic energy and weak intermolecular forces.
- Shape: Solids have a definite shape, liquids take the shape of the container, gases have no fixed shape.
- Kinetic Energy: Increases from solid to liquid to gas due to increasing particle movement.
- Density: Highest in solids, moderate in liquids, lowest in gases.
Question 3: 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 air but to do the same through a solid block of wood we need a karate expert.
Answer 3: (a) This is so because in a gas the attractive forces between the particles are negligible and molecules of a gas move with very high speeds in all possible directions.
(b) This is due to the bombardment of the molecules of a gas against the walls of the container.
(c) This is because it has a definite mass, volume and shape.
(d) This is because in air, the attractive forces between the particles are negligible but in a solid like block of wood, there are large attractive forces between the constituent particles.
Question 4: . Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.
Answer 4: In general, the volume of a liquid is more than the volume of a solid because liquid particles are freer to move, resulting in more volume. Ice, on the other hand, has a maximum density of water at 4 degrees Celsius. Ice is lighter than water and has a lower density. As a result, it floats on water.
In Text Questions Page No: 9
Question 1: Convert the following temperature
to celsius scale: a. 300 K b. 573 K
Answer 1: (a) 300 – 273 = 27°C (b) 573 – 273 = 300°C
Question 2: . What is the physical state of
water at: a. 250oC b. 100oC ?
Answer 2: (a) 250°C = gas (b) 100°C liquid as well as gas
Question 3: For any substance, why does the temperature remain constant during the change of state?
Answer 3: During the change of state of any substance, the heat supplied or released is utilised in phase change. Such heat is called latent heat. So, the temperature of any substance remains constant during the change of state.
Question 4: Suggest a method to liquefy atmospheric gases.
Answer 4: It can be achieved by either increasing the pressure or decreasing the temperature, which ultimately leads to the reduction of spaces between molecules.
In Text Questions Page No: 10
Question 1: Why does a desert cooler cool better on a hot dry day?
Answer 1: This is because on a hot dry day, the evaporation of water is faster due to higher temperature and lower humidity.
Question 2: How does water kept in an earthen pot (matka) become cool during summers?
Answer 2: An earthen pot or matka is generally made up of sand particles in which many tiny pores exist and this helps the water inside the pot to evaporate and surroundings makes the water cool. This is the reason why people kept the water in an earthen pot during summers.
Question 3: Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Answer 3: Acetone, petrol or perfume evaporate when they come into contact with air. The evaporation causes cooling sensation in our hands.
Question 4: Why are we able to sip hot tea or milk faster from a saucer than a cup?
Answer 4: A liquid has a larger surface area in a saucer than in a cup. Thus, it evaporates faster and cools faster in a saucer than in a cup. For this reason, we can sip hot tea or milk faster from a saucer than from a cup.
Question 5: What type of clothes should we wear in summers?
Answer 5: We should wear light-colored, loose, and cotton clothes in summers. They absorb less heat, allow better air circulation, and absorb sweat, keeping us cool.
Exercises
Question 1: Convert the following temperatures to the celsius scale.
(a) 293 K (b) 470 K
Answer 1: (a) 293 K into °C 293 – 273 = 20°C
(b) 470 K into °C 470 – 273 = 197°C
Question 2: Convert the following temperatures to the kelvin scale.
(a) 25°C (b) 373°C.
Answer 2: (a) 25 °C = (25 + 273) K = 298 K
(b) 373 °C = (373 + 273) K = 646 K
Question 3: 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.
Answer 3: (a) At room temperature, naphthalene balls undergo sublimation wherein they directly get converted from a solid to a gaseous state without having to undergo the intermediate state, i.e., the liquid state.
(b) Perfumes have high degree of vaporisation and its vapour diffuses into the air easily. Therefore, we can get the smell of perfume sitting several metres away.
Question 4: Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, oxygen.
Answer 4: Oxygen, Water, Sugar.
Question 5: What is the physical state of water at—
(a) 25°C (b) 0°C (c) 100°C
Answer 5: Physical state of water:
- (a) 25°C – Liquid
- (b) 0°C – Solid and liquid (both states coexist at melting point)
- (c) 100°C – Liquid and gas (both states coexist at boiling point)
Question 6: Give two reasons to justify—
(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.
Answer 6: (a) At room temperature water is liquid because the attractive forces between the molecules of water are small and can move from one point to another.
(b) An iron almirah is a solid because the particles are held together by strong intermolecular attractive forces and these particles are very close to each other.
Question 7: Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer 7: Here condition given that both ice and water are at same temperature i.e. 273 K. But ice at 273 K has less energy as compared to water this can be explained on the basis of latent heat of fusion which is possessed by water as an additional energy but ice does not have such type of energy. Therefore, we can say that at 273 K ice is more effective in cooling as compared to water.
Question 8: What produces more severe burns, boiling water or steam?
Answer 8: The intensity of burns in steam is more than that in boiling water because the particles present in steam have more energy than the particles present in water.
This extra energy is in the form of latent heat due to which they generate more heat. As a result, more burns are felt on the skin due to steam.
Question 9: Name A,B,C,D,E and F in the following diagram showing change in its state
Answer 9: Interconversion of three states of matter: Using temperature or pressure, any state of matter can be turned into another.
- (A) Solid to Liquid → Fusion or melting
- (B) Liquid to Gas → Evaporation or vaporization
- (C) Gas to liquid → Condensation
- (D) Liquid to Solid → Solidification
- (E) Solid to Gas → Sublimation
- (F) Gas to Solid → solidification