Matter in Our Surroundings
(Chapter-1)
Science Solution
Access to NCERT Class 9 Chapter-1,Matter in Our Surroundings
NCERT Textbook Questions
solved for Class 9 Science Page-wise.
Topics of C
hapter 1 Matter inhhhh Our Surroundings:
1.
Matter in Our
Surroundings
2.
Physical Nature of
Matter
3.
Characteristics of
Particles of Matter
4.
States of Matter
5.
Can Matter Change its
State?
6. Evaporation
Question 1. Which of the following are matters?
Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of
perfume.
Answer:
Chair, air, almonds,
and cold drink.
Question 2. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters away, but to get
the smell from cold food you have to go close.
Answer:
The smell of hot
sizzling food reaches several meters away, as the particles of hot food have
more kinetic energy and hence the rate of diffusion is more than the particles
of cold food.
Question 3. A diver is able to cut through water in a
swimming pool. Which property of matter does this observation show?
Answer:
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?
5.
THE
FUNDAMENTAL UNIT OF LIFE
6.
TISSUES
7.
MOTION
9.
GRAVITATION
10.
WORK
AND ENERGY
11.
SOUND
12.
IMPROVEMENT
IN FOOD RESOURCESAnswer:
The characteristics of
the particles of matter are:
(1) Particles have intermolecular space.
(2) Particles have intermolecular force.
(3) Particles of matter are moving continuously.
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:
Increasing density:
air < exhaust from chimneys < cotton < water < honey < chalk
< iron.
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Question 2. (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.
Answer:
(a) Difference in the
characteristics of 3 states of matter.
|
Characteristics |
Solid |
Liquid |
Gas |
|
1.
Shape 2.
Volume 3.
Rigidity/fluidity 4.
Intermolecular Force 5.
Intermolecular space 6.
Compresibility
|
Fixed
Shape Fixed
Volume are
rigid, not flow Maximum very
less negligible |
No
fixed Shap Fixed
Volume flow,
not rigidless than Solids more
than solids compressible |
No
fixed Shape No
Fixed Volume flow,
not rigidity very
less maximum
and less than gas High
compressible |
(b) Comment on:
This is a good summary
of some basic properties of matter. However, there are a few corrections and
additional points that could be made:
(i) Rigidity is indeed
the tendency of a substance to retain its shape when subjected to outside
force, but this property is more commonly referred to as "stiffness"
or "hardness". Rigidity is a related property that refers to the
ability of a material to resist deformation.
(ii) Compressibility: The
statement that "liquids and gases are compressible" is not entirely
accurate. While it is true that gases are highly compressible, liquids are only
slightly compressible. In fact, liquids are often considered to be essentially
incompressible for most practical purposes.
(iii) Fluidity: The tendency of particles to flow is
called fluidity. Liquids and gases flow.
(iv) Filling of a gas container: Gases have particles which vibrate
randomly in all the directions. The gas can fill the container.
(v) While it is true
that solids have a definite shape, it is worth noting that some solids can
exhibit a degree of plasticity or flexibility, allowing them to deform under
stress. Additionally, some materials exist in intermediate states between
solids and liquids, such as glasses, gels, and pastes, which do not have a
well-defined shape.
(vi) Kinetic energy: The energy possessed by particles due to
their motion is called kinetic energy. Molecules of gases vibrate randomly as
they have maximum kinetic energy.
(vii) While solids do typically have a higher density than liquids or gases,
this is not always the case. For example, some types of aerogels are incredibly
lightweight and have extremely low densities, despite being solid materials.
Overall, the
properties of matter are complex and varied, and can depend on a wide range of
factors such as temperature, pressure, composition, and structure.
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:
(a) The molecules of
gas have high kinetic energy due to which they keep moving in all directions
and hence fill the vessel completely in which they are kept.
(b) A gas exerts pressure on the walls of the container because the molecules
of the gas are in constant random motion due to high kinetic energy. These
molecules constantly vibrate, move and hit the walls of the container thereby
exerting pressure on it.
(c) The molecules/particles of wooden table are tightly packed with each
other, there is no intermolecular space, it cannot be compressed, it cannot
flow, all these characteristics are of solid. So 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. It is because the molecules of air has less
force of attraction between them and a very small external force can separate
them and pass through it. But in case of solids, the molecules have maximum
force of attraction, the particles are tightly bound due to this force. Hence
large amount of external force is required to pass through solid.
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 is a solid but its
density is lower than water due to its structure. The molecules in ice make a
cage like structure with lot of vacant spaces, this makes ice float on water.
Question 1. Convert the following temperature to Celsius
scale:
(a) 300 K (b) 573 K
Answer.
(a) 300 – 273 = 27°C
(b) 573 – 273 = 300°C
Question.2. What is the physical state of water at:
(a) 250°C (b) 100°C
Answer:
(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:
During the change of
state of any matter heat is supplied to the substance. The molecules of this
matter use heat to overcome the force of attraction between the particles, at
this period of time, temperature remains constant. This extra heat is acquired
by the molecules in the form of hidden heat called latent heat to change from
one state of matter to the other state.
Question 4. Suggest a method to liquefy atmospheric gases?
Answer:
The atmospheric gases
are taken in a cylinder with piston fitted on it. By cooling and applying
pressure on them, the gases can be liquefied.
Question 1. Why does a desert cooler cool better on a hot
dry day?
Answer:
The outer walls of the
cooler get sprinkled by water constantly. This water evaporates due to hot dry
weather. Evaporation causes cooling of inside air of cooler. This cool air is
sent in the room by the fan.
Question 2. How does
the water kept in an earthen pot (matka) become cool during summer?
Answer: The earthen pot is porous with lot of pores on it, the water
oozes out through these pores and the water gets evaporated at the surface of the
pot thereby causing cooling effect. This makes the pot cold and the water
inside the pot cools by this process.
Question 3. Why does our palm feel cold when we put some
acetone or petrol or perfume on it?
Answer:
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 rather than a cup?
Answer: Tea in a saucer has larger surface area than in a cup. The rate
of evaporation is faster with increased surface area. The cooling of tea in
saucer takes place sooner than in a cup. Hence we are able to sip hot tea or
milk faster from a saucer rather than a cup.
Question 5. What type of clothes should we wear in summer?
Answe: We should wear light coloured cotton clothes in summer. Light
colour because it reflects heat. Cotton clothes because it has pores in it,
which absorbs sweat and allows the sweat to evaporate faster thereby giving
cooling effect.
Question 1. Convert the
following temperatures to the Celsius scale.
(a) 293 K (b) 470 K.
Answer:
(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:
(a) 25°C into K
25 + 273 = 298 K
(b) 373°C into K 4 373 + 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) Naphthalene balls
disappear with time without leaving any solid, because naphthalene balls
sublime and directly changes into vapour state without leaving any solid.
(b) We can get the smell of perfume sitting several metres away because perfume
contain volatile solvent and diffuse faster and can reach people sitting
several metres away.
Question 4. Arrange the following substances in increasing
order of forces of attraction between the particles—water, sugar, oxygen.
Answer:
Oxygen —> water
—> sugar.
Question 5. What is the physical state of water at—
(a) 25°C (bj 0°C (cj 100°C
Answer:
(a) 25°C is liquid (b)
0°C is solid or liquid
(c) 100°C is liquid and gas
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:
(a) Water at room
temperature is a liquid because its freezing point is 0°C and boiling point is
100°C.
(b) An iron almirah is a solid at room temperature because melting point of
iron is higher than room temperature.
Question 7. Why is ice at 273 K more effective in cooling
than water at the same temperature?
Answer:
Ice at 273 K will
absorb heat energy or latent heat from the medium to overcome the fusion to
become water. Hence the cooling effect of ice is more than the water at same
temperature because water does not absorb this extra heat from the medium.
Question 8. What produces more severe bums, boiling
water or steam?
Answer:
Steam at 100°C will
produce more severe bums as extra heat is hidden in it called latent heat
whereas the boiling water does not have this hidden heat.
Question 9. Name A, B, C, D, E and F in the following diagram showing change in its state
Answer: A —> Liquefication/melting/fusion B —> Vapourisation/evaporation C—>Condensation D—> Solidification E —> Sublimation F —> Sublimation
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