Sameer blew onto a mirror surface and found that it became foggy. Why?
Because the air he breathed out contained water vapour and that water vapour condensed on touching the cold mirror surface forming a fog.
When a substance is cooled, the particles..........................
slow down
The process in which liquid changes into solid on cooling
Freezing
True /False: Opposite process of melting is freezing
True
Explain how puddles of water disappears on a sunny day.
the liquid water is heated by the sun. The liquid water evaporates and form water vapour.
The process of solid directly changing into a gas without passing through the liquid phase
sublimation
Matter is made up of extremely small particles known as ...................
Molecules
The increase in size of matter on heating is known as
Expansion
Three states of matter
solid ,liquid and gas
The process of transformation of a liquid to a solid at room temperature.
Solidification
True /False: You can change a solid into a liquid by freezing it.
False
Why do railway tract expand?
The railway track expands due to the heat of the sun and the frictional force(between wheels of train and track)
When a substance is heated ,the particles ....................
vibrate rapidly
Two examples of substances that solidify
ghee, butter, wax
The decrease in size of matter on cooling is known as
Contraction
The process in which solid changes into liquid on heating
Melting
Describe solid molecules in terms of particle arrangement
Molecules are tightly packed Strong intermolecular force of attraction Very less intermolecular space Molecules move about their fixed position
If a bottle of perfume is opened in one room, the scent quickly spreads to the other room.Why?
Because the gas molecules in perfume are very loosely packed and they move faster spreading everywhere.
Describe liquid molecules in terms of particle arrangement
Molecules are loosely packed Weak intermolecular force of attraction More intermolecular space between molecules Molecules in contact and slide over each other
Describe gas molecules in terms of particle arrangement
Molecules are very loosely packed Very weak intermolecular force of attraction Vast intermolecular space between molecules Molecules move in all directions
The process in which gas changes into liquid on cooling
Condensation
The process by which liquid turns into gas on heating
Evaporation
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