# NCERT Solutions for Class 9 Science Unit 1

## Matter in Our Surroundings Class 9

### Unit 1 Matter in Our Surroundings Exercise Solutions

Anything that has both mass and volume is called matter. For example - me, you, chair, table, computer, mouse, keyboard, dog, cat, cow, ram, pen, pencil, tree, plant, building, stone, brick, mountain, river, etc.
Early Indian philosopher categorized matter in five types and called them panch-tatwa (Five-elements) - Vayu (Air), Jal (Water), Agni (Fire), Prithvi (Earth) and Aakash (Sky).
According to science matters are divided according to their physical and chemical properties.

### Question : Solutions of Questions on Page Number : 3

Q1 :

Which of the following are matter?

Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.

Answer :

Anything that occupies space and has mass is called matter. Matter can exist in three physical states - solid, liquid, and gaseous.

Chair and almond are forms of matter in the solid state.

Cold drink is a liquid state of matter.

Air is a gaseous state of matter.

Note: The sense of smell is not matter. However, the smell or odour of a substance is classified as matter. The smell of any substance (say, perfume) can be classified as matter. This is because, perfume is in liquid state inside the bottle. It comes out in the form of tiny droplets. These droplets of perfume are matter and spread out in the atmosphere to create a sense of smell. This smell can be detected by our olfactory system.

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Q2 :

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 :

Solids diffuse at a very slow rate. But, if the temperature of the solid is increased, then the rate of diffusion of the solid particles into air increases. This is due to an increase in the kinetic energy of solid particles. Hence, the smell of hot sizzling food reaches us even at a distance, but to get the smell from cold food we have to go close.

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Q3 :

A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Answer :

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Q4 :

What are the characteristics of particles of matter?

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Q5 :

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 chimney, honey, water, chalk, cotton, and iron.

Answer :

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Q6 :

(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.

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Q7 :

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.

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Q8 :

Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

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Q9 :

Convert the following temperature to Celsius scale:

(a) 300 K

(b) 573 K

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Q10 :

What is the physical state of water at:

(a) 250°C

(b) 100°C

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Q11 :

For any substance, why does the temperature remain constant during the change of state?

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Q12 :

Suggest a method to liquefy atmospheric gases.

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Q13 :

Why does a desert cooler cool better on a hot dry day?

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Q14 :

How does water kept in an earthen pot (matka)become cool during summers?

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Q15 :

Why does our palm feel cold when we put some acetone or petrol or perfume on it?

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Q16 :

Why are we able to sip hot tea or milk faster from a saucer than a cup?

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Q17 :

What type of clothes should we wear in summers?

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### Exercise : Solutions of Questions on Page Number : 12

Q1 :

Convert the following temperatures to Celsius scale.

(a) 300 K

(b) 573 K

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Q2 :

Convert the following temperatures to Kelvin scale.

(a) 25°C

(b) 373°C

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Q3 :

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.

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Q4 :

Arrange the following substances in increasing order of forces of attraction between particles-- water, sugar, oxygen.

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Q5 :

What is the physical state of water at--

(a) 25°C

(b) 0°C

(c) 100°C

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Q6 :

Give two reasons to justify-

(a) water at room temperature is a liquid.

(b) an iron almirah is a solid at room temperature.

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Q7 :

Why is ice at 273 K more effective in cooling than water at the same temperature?

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Q8 :

What produces more severe burns, boiling water or steam?

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Q9 :

Name A, B, C, D, E and F in the following diagram showing change in its state.

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Science : CBSE NCERT Exercise Solutions for Class 9th for Matter in Our Surroundings will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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