CHEMISTRY [1 Mark Question Answer]

Glass, stone, pen.

Paper, sugar.

Naphthalene, camphor, dry ice.

Conversion of water into steam is boiling.

Conversion of ice into water is melting.

Disappearance of camphor is sublimation.

Formation of water vapour from water is vaporation.

Particles are far apart and move in all directions Gas

Particles are quite close together Solid

Particles move about very quickly Liquid

Matter can change from one state to another on changing temperature and pressure.

Intermolecular force of attraction.
Intermolecular spaces are two important properties of matter that account for the different states of matter

The process by which matter changes from one state to another and back to original state, without any change in its chemical composition.

The particles are free to move in any direction i.e. they can flow because all substances that can flow are called fluids.
Liquids and gases are fluids.

Solid: A solid is that state of matter which has a fixed shape, mass and volume. It suffers very small changes in volume by changing the temperature. It can not be compressed,
e.g. – Sand, Wood, Copper, Ice, etc.

Ice when kept at room temperature again changes back into liquid water.

Mass is the “quantity of matter” and weight is “the force with which the earth pulls a body towards itself’. The mass of a body does not change but its weight changes from place to place.

Sublimation .

this criteria is shown by atoms of any matter which may exist alone (like helium) or may not exist alone and exist in molecular form (like oxygen/o₂ )

Anything that has mass and occupies space is called matter.

The molecules can move only when there are gaps or space between them, this space is called intermolecular space.

The molecules of matter are always in motion and attract each other with a force called intermolecular force of attraction due to which they are held together.

Atoms may or may not have independent existance. Molecules have independent existance.

Molecules are made of atoms. Molecules exhibit the properties of that kind of matter and has independent exi stance.

The smallest particle from which matter is made up is atom.

Mass of a body does not change with change in gravity. So mass of a body will remain the same on moon.

Mass is the quantity of matter contained in the body.

If we put a drop of red ink in a glass of water, its particles diffuse with particles of water slowly but continuously and the water turns red.

This shows that gases can fill up all the space that they get, and they have neither a fixed shape nor a fixed volume. They have no free surfaces, either.

The molecules of liquid are loosely packed and intermolecular force of attraction is small but number of molecules in it remain the same. Hence liquids have definite volume but no definite shape.

The molecules of air are far apart i.e. large gaps and we can walk through air easily.

Intermolecular force of attraction is least and intermolecular spaces are very large, hence gases can fill up the space available to them.

Molecule — A molecule is a smallest part of a compound that exists independently.

Atom — An atom is the smallest part of an element that takes place in a chemical reaction.

Element — It is defined as that pure substance which contains only one type of atoms e.g. hydrogen, chlorine.

Intermolecular force — The force of attraction between the molecules of a given substance is called intermolecular force.

Matter—Anything that has mass and occupies space is called matter.

Electricity neither has mass nor it occupies space. Beside it can not be seen by our eyes. This is why electricity is not considered matter.

We need to classify things in order to distinguish them. In this way, things can be categorized and can be easily studied.

In liquids intermolecular force is weaker than that of solids. So molecules in a liquids can slip over one another and liquids can flow unlike solids.

The reason for this property of gases is that there is very large intermolecular space between gas molecules. On mere applying pressure, they are easily compressed.

The amount of space occupied by a matter is called its volume.

Two conditions are : change in

1. Temperature
2. Pressure

The process by which matter changes from one state to another and back to original state, without any change in its chemical composition.

Substances that can flow are called fluids, e.g. gases (oxygen, hydrogen), liquids (water, petrol, sulphuric acid).