Table of Contents
About PSEB 9th Class Science Ch1 Matter in Our Surroundings
Chapter 1 of the PSEB 9th Class Science book, “Matter in Our Surroundings,” explores the various forms of matter and their properties. The chapter introduces the concept of matter and its three states – solid, liquid, and gas. It explains how matter can change its state through heating or cooling, and the factors that affect these changes. The chapter also discusses the physical properties of matter such as mass, volume, and density, as well as the concept of the particle theory of matter. Additionally, it touches upon topics like evaporation, condensation, and sublimation. Overall, this chapter provides a foundation for understanding the nature of matter and its behavior in our everyday surroundings.
Science Guide for Class 9 PSEB Matter in Our Surroundings InText Questions and Answers
Q.1. Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, lemon, water, smell of perfume.
Ans. Anything that occupies space and has mass is,known as matter. So Chair, air, almond, lemon, water and smell of perfume are matter.
Q.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.
Ans. Particles of food that carry smell diffuse in air at very high rate when food is hot. This is because kinetic energy of particles is increased with raise in temperature. On the other hand particles from cold food possess less kinetic and thus cold
Q.3. A diver is able to cut through water in a swimming pool. Which property of matter does
this observation show?
Ans. This shows matter is made up of small particles. And Particles of matter have space between them.
Q.4. What are the characteristics of the particles of matter?
Ans. 1) Particles of matter have space between them.
2) Particles of matter are continuously moving.
3) Particles of matter attract each other.
In text Questions -Page- 6
Q.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.
Ans. Increasing order of density:-
Air < Exhaust from chimneys<Cotton<Water<Honey < Chalk < Iron
Q.2 (a) Comment upon the following:
rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.
Ans. Comments are as follows:-
1) Rigidity:- Tendency of matter to resist change in its shape is known as rigidity.
2) Compressibility:- Ability of matter to be reduced to lower volume is known as compressibility.
3) Fluidity:- Ability of matter to flow is called Fluidity.
4) Filling a gas container:- Attainment of shape of a container by gas is called filling a gas container.
5) Shape:- Shape defines a definite boundaries.
6) Kinetic Energy:- Energy possessed by a particle due to its motion is called kinetic energy.
7) Density:- The mass per unit volume of a substance is called density.
density = Mass / volume
Q.2.(b) Tabulate the differences in the characteristics of states of matter.
Ans. Table is given below:-
(a) Differences in the characteristics of states of matter:
| Characteristics | Solid | Liquid | Gas |
| 1. Vacant spaces | Very small | Small | Very large |
| 2. Attractive forces between particles | Very large | Small | Negligible |
| 3. Compressibility | Negligible | Low | High |
| 4. Rigidity | High | Low | Not rigid |
| 5. Density | High | Low | Very Low |
| 6. Energy | Small | Large as compared to solid |
Question 3 Give reasons:
(a) A gas fills completely the vessel in which if is kept.
ANS – This is because in a gas the attractive forces between the molecules are negligible and molecules of a gas move with very high speeds in all possible directions.
(b) A gas exerts pressure on the walls of the container.
ANS This is due to the hits or bombardments of the molecules of a gas against the walls of a container.
(c) A wooden table should be called a solid.
ANS This is because it has a definite mass, volume and shape.
(d) We can easily move our hand in air but to do the same in solid block of wood we need a Karate expert.
Answer: (d) This is because in air, the attractive forces between the particles are negligible but in a solid 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: Ice floats over water because ice has lower density than liquid water. This is because in ice for a given mass volume is more as compared to in liquid water.
Question 9. Convert the following temperature to Celsius scale:
(a) 300 K
(b) 573 K?
Answer:
(a) 300 K = 300 – 273 = 27°C.
(b) 573 K = 573 – 273 = 300°C.
Question 10. What is the physical state of water at:
(a) 250°C
(b) 100°C?
Answer:
(a) Gas
(b) Gas
Question 11. For any substance, why does the temperature remain constant during the change of state?
Answer: This is because the heat supplied is used to overcome the attractive forces between the particles i.e., there is change in potential energy.
Question 12. Suggest a method to liquefy atmospheric gases.
Answer: The atmospheric gases can be liquefied by cooling under pressure.
Question 13. Why does a desert cooler cool better on a hot dry day?
Answer: On a hot dry day due to increase in temperature and lesser humidity the evaporation of water will be faster
Question 14. How does the water kept in an earthen pot (matka) become cool during summer?
Answer: This is because the water comes out from the pores of earthen pot (matka) and it evaporates. Due to evaporation it causes cooling.
Question 15. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Answer: This is because the particles of acetone or petrol or perfume gain energy from our palms and surroundings and evaporate causing cooling.
Question 16. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Answer: Because a saucer provides more surface area than a cup for evaporation of liquid into vapour and it causes a more cooling effect.
Question 17. What type of clothes should we wear in summer?
Answer: White cotton clothes
PSEB 9th Class Science Guide Matter in Our Surroundings Textbook Questions and Answers
Question 1. Convert the following temperature to the Celsius scale:
(a) 293 K
(b) 470 K.
Answer:
(a) 293 K = 293 – 273 = 20°C
(b) 470 K = 470 – 273 = 197°C
Question 2. Convert the following temperatures to the Kelvin scale:
(a) 25°C
(b) 373°C.
Answer:
(a) 25°C – 25 + 273 = 298 K
(b) 373°C = 373 + 273 = 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: (a) This is because naphthalene sublimes i.e. it directly changes into vapour without melting.
(b) This is because the molecules of perfume are moving with very high velocities (i.e. diffusion) in all the directions.
Question 4. Arrange the following substances in increasing order of forces of attraction between the particles-water, sugar, oxygen.
Answer: The increasing order of intermolecular forces of attraction is Oxygen < Water < Sugar.
Question 5. What is the physical state of water at:
(a) 25°C
(b) 0°C
(c) 100°C?
Answer:
(a) At 25° C, water is liquid.
(b) At 0° C, water is solid (Ice).
(c) At 100° C, water is gas (Steam).
Question 6. Give two reasons to justify that:
(a) Water at room temperature is a liquid.
(b) An iron almirah is a solid at room temperature.
Answer:
(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 solid because the molecules are held together by strong intermolecular attractive forces and the molecules or 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: Ice at 273 K is more effective in cooling than water at 273 K, this is because in ice, the molecules have lower energy as compared to the particles in the liquid water at the same temperature (273 K) and require latent heat of fusion for melting.
Question 8. What produces more severe bums: boiling water or steam?
Answer: Steam produces severe burns as compared to boiling water. This is because in steam the molecules have higher kinetic energy than in boiling water.
Question 9. Name A, B, C, D, E and F in the following diagram showing state change-
Answer:
A – Fusion
B – Vaporisation
C – Condensation
D – Solidification
E – Sublimation
F – Sublimation
EXTRA IMPORTANT QUESTION ANSWER
Q: What is matter?
A: Matter refers to anything that occupies space and has mass. It can be solid, liquid, or gas.
Q: How does matter change its state?
A: Matter can change its state through heating or cooling. By adding heat energy, a solid can melt and become a liquid, and further heating can turn the liquid into a gas. Conversely, by removing heat energy, a gas can condense into a liquid, and further cooling can cause the liquid to solidify.
Q: What are physical properties of matter?
A: Physical properties are characteristics that can be observed or measured without changing the composition of the substance. Examples include mass, volume, density, color, and texture.
Q: What is the particle theory of matter?
A: The particle theory of matter states that all matter is made up of tiny particles called atoms or molecules. These particles are constantly in motion and have spaces between them. The behavior of matter is determined by the arrangement, movement, and interaction of these particles.
Q: What is evaporation?
A: Evaporation is the process by which a liquid changes into a gas at a temperature below its boiling point. It occurs when the particles on the surface of the liquid gain enough energy to overcome the forces of attraction and escape into the air.
Q: What is condensation?
A: Condensation is the opposite of evaporation. It is the process by which a gas changes into a liquid when it loses heat energy. The gas particles slow down, come closer together, and form liquid droplets.
Q: What is sublimation?
A: Sublimation is the process in which a solid directly changes into a gas without passing through the liquid state. It occurs when the particles of the solid gain enough energy to overcome the forces of attraction and escape into the air as gas particles.
Q: Why is understanding matter important?
A: Understanding matter is crucial as it helps us comprehend the properties and behavior of substances around us. It forms the foundation of various scientific disciplines, such as chemistry and physics, and provides insights into the changes and reactions that occur in our everyday life. Moreover, understanding matter aids in practical applications like material science, engineering, and environmental studies.