Matter in Our Surrounding Test - 9

A solution of potassium permanganate (KMnO₄) is not orange. It is purple in colour. Crystals of potassium permanganate dissolve in water to give intensely pink or purple solutions.

Matter is composed of very small particles called atoms, hence matter is not continuous but particulate in nature. However, there is another nature associated with matter, which is wave like nature. Sub-atomic particles like electrons very well exhibit wave nature along with particle nature. However this wave nature is not shown by macroscopic objects which are easily observable. The wavelength that is associated with these objects is too small and not appreciable.

The melting point of a solid is an indication of the strength of the force of attraction between its particles. So, solid B has more intermolecular force of attraction.

(1) Dry ice is solid form of carbon dioxide (CO₂). It is used primarily as a cooling agent.
(2) Humidity is the amount of water vapour present in the air. The air around us cannot hold more than a definite amount of water vapour at a given temperature. If the amount is already high, the rate of evaporation decreases.
(3) Evaporation increases with increase in temperature and decreases with decrease in temperature. This means rate of evaporation is directly proportional to the temperature.
(4) A gas can be liquefied easily by increasing the pressure (i.e. by compression), and reducing the temperature (i.e. by cooling).

(1) Fluidity is the flow or motion of particles in a state of matter.
(2) Rigidity is inflexibility or resistance to change in shape. Solids have a tendency to maintain their shape when subjected to outside force. Solids may break under force but it is difficult to change their shape, so they are rigid.
(3)The mass per unit volume of a substance is called its density. Mass is an intrinsic property of a substance. Volume is the space occupied by the substance.
(4) A state of matter exhibits incompressibility when the state of matter has negligible intermolecular spaces. Solids have negligible compressibility. Gases are highly compressible as compared to solids and liquids.

Characteristics of Particles of Matter

1. Particles of matter have space between them – When we dissolve sugar, salt or potassium permanganate in water, particles get evenly distributed in water. Particles of one type of matter diffuse into the space between particles of the other.
2. Particles of matter are continuously moving – Particles of matter are continuously moving, they posses kinetic energy which increase with increase in temperature.
3. Particles of matter attract each other – Particles of matter have force acting between them, these forces keeps the particles together. The strength of this force of attraction varies from one kind of matter to another.

A change of state directly from solid to gaseous without changing into liquid or vice versa is called Sublimation.

The physical state of matter is defined by the intermolecular spaces between them. The gases have the highest empty space between them while the liquids have comparatively lower space. Hence the gases can be liquefied by reducing the gap between the molecules. This can be done either by reducing the temperature or increasing the pressure.

The process of changing liquid into gases (vapour) even below its boiling point is called evaporation.  The rate of evaporation increase with the increase in temperature, surface area and wind speed.

Solid carbon dioxide can be changed into vapours or gaseous state by decreasing the pressure and/or increasing the temperature. Both the processes increase the spaces between the constituent particles. They also increase the kinetic energy of the particles.