5 – Substances in The Surroundings –
Their States and Properties
Q. 1. In a
paragraph below, write 'solid'. 'liquid' or 'gas' in each of the brackets depending on the substance referred to just before :
Ans. On a bright sunny day, Riya and Gargl are playing with
a ball (solid) in the park. Gargt feels thirsty. So Riya brings tender coconut
water (liquid) for her time, a strong breeze (gas) starts blowing and it also
begins to rain (liquid) back into the house (solid). change their clothes
(solid) and then their mother gives
them a cup (solid) of hot milk
(liquid) to drink.
Q. 2. Who am I?
(1) I'm found in a thermometer. I measure temperature. Mercury
(2) I make things hot or cold.
Heat
(3) I have no shape whatsoever ! Liquid and gas
(4) I dissolve in water, but not
in kerosene. Salt
Q 3. Write the properties of these substances:
Ans. (1) Water :
(1) Water in liquid form is used by every living organism. (2) In solid
state it turns into ice. (3) In gaseous state it is a
vapour. (4) Boiling point and condensation point of the water is 100 °C. (5)
The melting point and freezinig point of water is 0 °C. (6) Many substances can
dissolve in water, therefore it is
called universal solvent.
(2) Glass : (1) Glass is a solid substance. (2) Silica or sand is
melted to make glass
(3) Brittleness is the characteristic feature of glass. (3)
If there is pressure on glass
it turns into fine particles.
(3) Chalk : (1) Chalk is a solid substance. (2) It is insoluble in
water. (3) Brittleness
is a character of chalk. (4) If pressure is applied, chalk
forms fine particles.
(4) Iron ball : (1) Iron is a solid metal. (2) The iron has both
malleability and ductility. (3) The iron can be used to make sheets or wires.
Many equipment are manufactured due to iron. (4) Iron has
electrical conductivity and thermal
conductivity. Therefore many
machines are made of iron. (5) Iron also has sonority,
(5) Sugar : (1)
Sugar is a solid and particulate matter. (2) Sugar is soluble in water (3)
After dissolving in water it forms sugar solution.
(6) Salt: (1) Salt is particulate, solid chemical compound. (2) It is
soluble in water
but insoluble in kerosene. (3) It is salty to taste. It
forms salt solution after
dissolving in water.
(7)Flour: (1) Flour is particulate and solid matter which is obtained
after the grains
are ground finely. (2) It is insoluble in water. (3) By
adding water to the flour, a
solid substance is prepared.
(8) Coal: (1) Coal is solid substance that is inflammable. It is
brittle and hence if pressure is applied it is crushed into particles. Coal is
used as a
fuel.
(9) Soil: (1) Soil is a solid substance. (2) It is a mixture of many
soluble and insoluble
substances.
(10) Pen : (1) Pen is a man-made product made from plastic and metals.
(2) it contains the solution of ink, so that we can write with it.
(11) Ink : (1) Ink is a liquid substance. (2) It is of different colours.
(12) Soap : (1) Soap is of different types. Some soaps are solid while
some are in
liquid form. (2) Some soaps are in the form of a block while
some are in the form of powder. (3) Soaps are soluble in water and they form
soap solution (4) Soaps are
made from different chemicals.
Q. 4. What is
it made from? Why?
(1) A sickle to cut sugarcane :
Ans. The sickles used for cutting sugarcane are made from
iron or other strong metals. Hardness, malleability, and ductility are the
characteristics of iron. Therefore it is ideal to use it in making of sickle.
For cutting the sugarcane we need a strong equipment
(2) The sheets used for roofing:
Ans. The sheets used for roofing houses are made from
aluminium. Aluminium is a metal that is
light in weight and is durable and rust free. It can protect the house well
from rains and sun.
(3) A screwdriver:
Ans. The screwdriver is made from a good quality steel.
Steel is a mixture of different metals. It is strong and is thus helpful in
joining nuts and bolts. The work done by screwdriver thus becomes efficient.
(4) A pair of tongs :
Ans. In olden times, a pair of tongs were made from iron,
but now they are made from stainless steel, which is durable, strong and rust
free. Usually in a kitchen this equipment is used and hence it is made from
high quality metals.
(5) Electric cables :
Ans. Electric cables are either of copper or aluminium.
Copper is a good conductor of electricity. Therefore, most of the electric
cables are made from copper.
(6) Ornaments :
Ans. Ornaments are made from gold or silver. Nowadays
platinum is also used for making ornaments. All these metals have
characteristic of ductility. Hence they can be stretched and pulled in the form
of wires. Making ornaments from these metals thus becomes easier. Diamonds are
also studded in ornaments. Diamond is the hardest substance and has shine. Gold
and silver have lustre which makes ornaments shine.
(7) Pots and pans :
Ans. Pots and pans are made from different metals.
Aluminium, stainless steel and brass are the common choices. Cooking food becomes
easier in them. All the metals have a characteristic of thermal conductivity.
In pots of stainless steel, the chemical reactions with the food do not take
place. Therefore, it becomes convenient to use such materials.
Q 5 What is sublimation ? Write the names of everyday
substances that sublimate.
Ans. The change in the solid substance without changing into
liquid is called sublimation.
The substances that
show sublimation are : Camphor, Naphthalene balls, iodine crystals, Ammonium
chloride or navsagar.
Q 6 Why does
this happen ? OR Give reasons.
(1) Coconut oil
thickens in winter.
Ans. In winter, the temperature of air is less. At this
temperature the freezing point of
coconut oil is reached. Therefore it freezes and appears to
be thickened.
(2) Kerosene left
in an open dish disappears.
Ans. The kerosene left in an open dish gets evaporated. The
temperature of the surrounding hastens this process of evaporation and thus the
kerosene completely evaporates and disappears.
(3) The fragrance of incense sticks lighted
in one corner of a room spreads to the other corner.
Ans. When fragrance sticks are lighted they emit fragrant
smoke. This smoke is in the form of gas and thus can spread anywhere. With the
smoke the fragrance also reach the entire room and thus the fragrance of
incense sticks lighted in one corner of a room spreads to the other corner.
(4) What do you see in the picture?
Ans. We see that the air filled balloon put in the trough of
water is floating but the apple sinks to the bottom. Apple is a solid substance
and hence its density is more. Balloon floats as it is filled with air, i.e. a
gaseous substance.
Q 7 What will
happen if ? And why?
(1) Nails are made of plastic.
Ans. Nails
should be made from metals that have characteristic of hardness. Plastic is a
brittle substance. It cannot withstand hammering, neither it can enter the
material in which we may try to pierce them. Therefore nails made of plastic
cannot be used.
(2) A bell is made of wood.
Ans. Sonority is the characteristic of metals.
The sound produced by metal bell would be melodious. Similar sound cannot be
produced by wooden bell as wood does not have characteristic of sonority.
(3) Rubber is not fitted on a pair of tongs.
Ans. Pair of
tongs are made of metals. They will get heated due to thermal conductivity,
during the use in the kitchen. If they are not fitted with rubber, they may
cause burns. This can hurt us.
(4) A knife is made of wood.
Ans. The wood is not metal and is thus not
hard. The work of knife cannot be performed by the wooden knife. It cannot cut
the objects due to lack of hardness.
(5) An axe is made of rubber.
Ans. Rubber is a substance having elasticity.
The rubber axe will rebound when hit upon an object. The metal axe can perform
a function as the metals are hard substances. The rubber axe will not be able
to do this function.
