What is matter? What are the different states of matter around you?
Matter is anything that occupies space and has mass. The different states
of matter are solid, liquid and gas.
Classify the following materials given on the basis of their physical
states?
Stone, pencil, water, air, oxygen, kerosene, desk, crayon, nitrogen,
petrol, milk, sugar, carbon dioxide, vinegar, neon
What are the properties of solids?
Solids have definite mass, definite volume and permanent shape.
What are the properties of liquids?
Liquids have definite mass, definite volume and donot have definite shape.
What are the properties of gases?
Gases have definite mass but donot have definite volume and permanent
shape.
What is each substance made of?
Each substance is made of tiny
particles which cannot be seen with naked eyes. These particles bear all the
properties of the substance.
What are the
characteristics of particles of substances?
Some characteristics of particles
of substances in different physical states are listed below
Øparticles have
a distance between them.
Øparticles move
continuously.
Øparticles attract one another.
Is the arrangement of particles in the solid, liquid and gaseous states the same?
No
In which of
these states do particles remain very close to each other?
In solids
In which of
these states are the particles most distant apart?
In gases
Change of state
Which form of energy is responsible for the change of state?
Heat energy
What are the changes that happen to the following properties when heat is absorbed by substances?
energy of
particles : Increases
distance
between particles : Increases
attraction
between particles : Decreases
movement of
particles: Increases
Properties of particles in solids, liquids and gases
ØThe particles
of solid are very close to each other. Their freedom of movement is
limited.
ØIn the liquid
state, particles are relatively farther apart and have more freedom of movement
than in the solid state.
ØIn the gaseous
state, particles remain far away from one another. Their freedom of movement is
very high.
What happens
when a solid is heated?
When a solid is heated the energy
and movement of particles increase and attraction among particles decrease.
When the particles attain sufficient energy the solid changes to liquid. This
change of state from solid to liquid is known as liquefaction.
What happens when a liquid is heated?
When a liquid is heated the
energy and movement of particles increase and attraction among particles
decrease. When the particles attain sufficient energy the liquid changes to
gas. This change of state from liquid to gas is known as vapourisation.
What is
sublimation?
Some substances, when heated,
change directly into gas without forming liquid. This phenomenon is sublimation.
What happens
when a gas is cooled?
When a gas is cooled energy and
movement of particles decrease and attraction among the particles increase. The
gas changes to liquid. This change of state from gas to liquid is condensation.
What happens
when a liquid is cooled?
When a liquid is cooled energy
and movement of particles decrease and attraction among the particles increase.
The liquid changes to solid. This change of state from liquid to solid is soldification.
Name some substances which undergo sublimation.
Camphor, Naphthalene, Iodine
Diffusion
Diffusion is the spontaneous mixing of different particles having freedom
of movement.
An incense
stick has fragrance. But the fragrance fills the room only when the stick is
lit. Why do the fragrance spreads quickly in the room when the incense stick is
lit?
The fragrance fills the room only
when the incense stick is lit. When the incense stick is lit the freedom of
movement of the fragrant particles increase.
The fragrance spreads because its particles are diffused in air.
Is there any
relation between temperature and diffusion?
Yes, there is relation between temperature and diffusion. When temperature increases freedom of movement of particles increase. As a result diffusion increase.
Why does the
smell of hot food spread quickly to a long distance?
In hot food the energy of particles is more. Therefore the particles
diffuse faster in air and spread quickly to a long distance.
Find more
examples for diffusion from daily life
Spreading of the smell of fruits.
Spreading of the smell of
perfumes.
Diffusion of smoke in air.
Ink diffuses when a drop is added to water.
Pure substances
Materials made of particles of
identical nature are called pure substances.
Mixtures
The substances made of particles
of different nature are called mixtures.
Separating the
Components of a Mixture
List a few instances where
components of mixtures are to be separated:
•
separating husk (chaff) from paddy.
•
separating tea dreg from tea.
•
separating common salt from sea water.
•
Iron powder from a mixture of iron powder and aluminium powder
Complete the table given below.
What does the
method of separation of components depends?
The choice of the method of
separation of components depends on the properties of the components of a
mixture.
The method used
for separating pure water from sea water is __________.
Ans: distillation
When do the
method of distillation is used for the separation of components?
When one component of the mixture is volatile and the others do not vapourise under the same condition, they can be separated by distillation. If the components of a mixture possess a large difference in their boiling points, they can be separated by distillation.
Explain the method of distillation of common salt
solution.
Salt water is taken in a round bottomed flask. One end of a condenser is connected to this flask and the other end is connected to an another round bottomed flask. These are arranged in such a way that the flask in which salt water taken is at a higher position than the other flask. Then heat the salt solution. Water evaporates because boiling point of water is less than the boiling point of salt. Salt remains in the flask. When water vapour is passed through the condenser it gets cooled and is collected in the second flask.
What is the use of distilled water?
Distilled water is used for injection and in storage battery.
When do fractional distillation is used for
separating components?
If the boiling
points of components have very small differences, fractional distillation is to
be used to separate them.
Ethanol
(boiling point 78℃) and methanol
(boiling point 65 ℃) are two
miscible liquids. There is only a small difference in their boiling points.
These two liquids are separated from their mixture by fractional distillation.
Briefly explain the method of fractional
distillation?
For fractional distillation a fractionating column is used. When vapours of the mixture pass through the fractionating column, repeated liquefaction and vapourisation take place. Subsequently, the vapours of low boiling methanol enter the condenser from the fractionating column, condense to liquid and get collected in the round bottomed flask first. Similarly, ethanol with higher boiling point can be collected later in another round bottomed flask.
Separation using separating funnel
Separating funnel is an apparatus used for
separating immiscible liquids from their mixture. If water and kerosene are
mixed we can use a separating funnel to separate these liquids. Water and kerosene
are immiscible liquids. Take this mixture in a separating funnel. Kerosene will
float over water, because the density of water is more than that of
kerosene. Open the stopcock and collect
the water in a beaker. When entire water is drained , close the stopcock.
Separation using the method of sublimation
If one of the components in a mixture has the
property of sublimation, the following method can be adopted for separating the
components. For example if sand is mixed with substances like ammonium chloride,
naphthalene, camphor etc. this method
can be used for separation. Take the mixture in a china dish. Put a funnel
upside down on the china dish to cover the mixture. Close the tail end of the
funnel with cotton. Then heat the mixture. The substance which has the property
of sublimation will evaporate. This vapour will solidify on the inner walls of
the funnel.
Separation using the method of centrifugation
This is a method for separating components from a
mixture, based on the difference in the mass of particles. This method is used
in clinical laboratories to separate blood cells from blood samples and also
for the quick separation of the precipitate obtained during chemical
experiments. The liquid containing the sample is taken in a test tube and is
rotated about a central point in the instrument. The particles with higher mass
then get separated, away from the centre and those with lower mass remain
closer to the centre. This method is used for separating butter from curd.
What is centrifugation?
In order to separate insoluble particles in a liquid mixture on the basis of their mass difference, Centrifuge is used. The process is known as centrifugation.
What is chromatography?
Chromatography is the method used to separate more
than one solute dissolved in the same solvent. This method was first employed
for separating coloured substances and hence this process came to be known as
Chromatography.
List some
instances when chromatography is used for the separation of components.
•
to separate components from dyes.
•
to separate poisonous substances mixed with
blood.
Answer:
2. Given below are certain changes taking place to the
particles during change of state. From this, find out and tabulate the changes
in the particles when water boils to form steam and also when steam condenses
to form water.
•
distance increases
•
attractive force decreases
•
energy increases
•
rate of movement increases
•
distance decreases
•
energy decreases
•
attractive force increases
•
rate of movement decreases
Answer:
3. Spirit kept open in a watch glass disappears after
some time. Which among the following phenomena are responsible for this?
a)
sublimation b) distillation
c)
evaporation d) diffusion
Ans: Evaporation
4. Which are the methods that can be used to separate the
components of a mixture made of common salt, ammonium chloride and sand?
Write the methods in the order in which they are applied.
Ans:
Methods can be used are, Sublimation,
Dissolution, Filtration, Evaporation.
Heat the mixture, ammonium
chloride will undergo sublimation. Add water to the remaining mixture. Salt
will dissolve in water. Separate sand and salt solution by filteration. Salt
from salt solution can be separated by evaporation.
5. Many minerals are present in ordinary water.
a) Which is the method that can be used to remove the
minerals and obtain pure water?
b) In which type of mixtures is this method employed?
c) Water purified by this method is distilled water Write
two instances of its use.
Ans:
a) Distillation
b)When one component of the mixture is volatile and the others do not vapourise under the same condition, they can be separated by distillation. If the components of a mixture possess a large difference in their boiling points, they can be separated by distillation.
c) Distilled water is used for injection and in storage battery.
6. From the following statements, tick those which apply
to solid substances alone.
•
Particles have little freedom of
movement.
•
Distance between particles is
very high
•
Particles remain very close to
each other
•
Energy of particles is very high
Answer:
.png)
.png)
.jpg)
.png)
.png)
.jpg)
.jpg)
.jpg)
0 Comments