Class 9 Science - Chapter Matter in Our Surroundings NCERT Solutions | Give reason for the following observatio

What type of clothes should we wear in summer?

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

Give two reasons to justify—

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

Suggest a method to liquefy atmospheric gases.

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.

Which of the following are matter?

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

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.

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.

Convert the following temperature to celsius scale:

a. 300 K              b. 573 K.

Convert the following temperatures to the Kelvin scale.

(a) 25°C              (b) 373°C.

Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?

State the universal law of gravitation.

A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force (Fig. 11.3). Let us take it that the force acts on the object through the displacement. What is the work done in this case?

What is meant by a pure substance?

How does the sound produced by a vibrating object in a medium reach your ear?

In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.

sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water

What are canal rays?

State any two conditions essential for good health.

How is our atmosphere different from the atmospheres on Venus and Mars?

Who discovered cells, and how?

What do you think would be the observation if the α-particle scattering experiment is carried out using a foil of a metal other than gold?

What does a neuron look like?

What is the greenhouse effect?

What is the acceleration of free fall?

Why is water essential for life?

Why are sound waves called mechanical waves?

What is a tissue?

State any two conditions essential for good health.

Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s^-1 and 1 m s^-1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s^-1. Determine the velocity of the second object.

An object of mass 100 kg is accelerated uniformly from a velocity of 5 m s^-1 to 8 m s^-1 in 6 s. Calculate the initial and final momentum of the object. Also, find the magnitude of the force exerted on the object.