Solid liquid and gas
Solid-liquid and gas
Freezing
On cooling, the molecules in the liquid slow down for
forming regular bonds between them. Thus, lovely crystals form, when water
freezes to snowflakes.
What is Matter?
MATTER IS EVERYTHING AROUND US. Any substance in the universe
that takes up space is known as matter. The matter is found in three different
forms or states in solid form, like a brick, in liquid forms, like water, and in
the form of gas, like air. At the right temperature and pressure, any substance
can change its form and reverse again. For example, the liquid, water, turns
into ice and ice turns into water.
Solid
A strong substance that has a definite shape is solid. Every substance is
made from very tiny
bits called molecules.
Molecules are so small that they cannot be seen. In a
solid substance, the molecules
are bonded together firmly in a
regular structure. All molecules
keep moving all the time, but
molecules simply vibrate on the
spot in a solid. AS it gets hotter, the molecules vibrate more and more.
Liquid
Any substance that flows like water and takes the shape of the
container it is poured into is a liquid. This happens because, in a liquid, the
bonds that hold the molecules together are so loose that molecules roll over
each other like dry sand.
Gas
When any substance is in an air-like state the molecules in it move so fast that the bonds that hold them together are broken and the substance has no strength, shape, or volume. Then the substance is a gas.
Ancient home
The state of any substance, liquid, solid or gas, depends on
the bonds between the molecules the substance is made of. With a rise in
temperature, the bonds get looser, as the molecules move more.
Melting and boiling
Melting is when a solid turns to liquid as heat causes the molecules
in the matter to vibrate so much that the bonds that hold them together get loosened.
If it becomes even hotter, the molecules move all over the place so fast they break
away from the surface of the liquid to become gas.
Three forms of water
Ice, water and water vapor are the three states, in which
water exists naturally on Earth. Water vapour or steam is lots of very tiny
drops of water:
Question
1. At what temperature does water boil?
(a) 50'C
(b) 100'C
(c) 1000'C
2. What is the freezing point of helium, the lowest freezing
point of any substance?
(a) -272.2"C
(b) 12.5°C
(c) -1.1'C
3. What is the melting point of tungsten, the highest
melting point of any metal?
(a) 320°C
(b) 420'C
(c) 7,890'CC
4. Which is the substance with the highest melting point?
5. What is the meaning of condensation?
6. What is meant by melting point?
7. Which is the metal that is liquid at room temperature?
8. In which states of matter do clouds contain water?
Answers
I. (b)
2. (a)
3. (b)
4. Carbon
5. The change from gas to liquid
6. The temperature at
which a substance changes from a solid to a liquid
7. Mercury
8. All three
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