States of Matter

Matter generally exists in three states; solid, liquid and gas. In solids, the particles are very close to each other and they have very strong inter-particle forces of attraction between them. 

Option (3) is correct.

A diver is able to cut through water in a swimming pool because the force of attraction among the particles is less. If the force had been strong, the diver would not have been able to cut that force. Moreover, the particles of water are continuously moving with some kinetic energy (although the magnitude of kinetic energy is not very high). They don’t possess potential energy.

The particles of matter possess kinetic energy and thus, are constantly moving. Kinetic energy of particles is directly proportional to the temperature. The temperature of hot food is more, so the particles of hot vapours coming out of hot sizzling food have higher kinetic energy, i.e. they move faster and hence, the smell of hot sizzling food reaches several metres away. Moreover, the particles in vapour state do not have forces of attraction and they can easily move.

100^oC is the boiling point of water, i.e. it is the temperature at which liquid starts boiling at the atmospheric pressure. Therefore, at this temperature both liquid and gaseous states of water can co–exist. Once boiling point is reached, the temperature of the system will remain constant until all water changes to gaseous state because the heat supplied is used to overcome the forces of attraction between particles of water so as to change it into gaseous state. At 99^oC, water will exist in liquid and at 101^oC, water will exist in gaseous state. At 0^oC (i.e. Melting point of ice) both ice and water will co-exist as at this temperature, ice starts melting. The heat supplied is used to overcome the forces of attraction between the particles so as to convert it into liquid state. The temperature will remain 0^oC until all the ice changes into liquid and therefore, at 0^oC, both solid and liquid states will co-exist.

When we pour some acetone (nail polish remover) on our palm, we feel cool. This is because particles gain energy (equal to latent heat of vapourisation) from our palm or surroundings and evaporate, causing the palm to feel cool. the palm will not get heated. It will not become red and it will not pain as nail polish remover does not harm our skin.

During summers, we perspire more because of the mechanism of our body which keeps us cool. Cotton, being a good absorber of water, helps in absorbing sweat and exposing it to the atmosphere so that particles of sweat gain energy equal to latent heat of vapourisation from the surroundings and evaporate, leaving the body cool.

Torr is a unit of pressure.

Helium is mixed with oxygen for respiration by divers in deep sea.

The smell of the perfume spreads in the room within a short period due to diffusion. Diffusion is the net movement of molecules or atoms from a region of high concentration (or high chemical potential) to a region of low concentration (or low chemical potential). The rate of diffusion of liquids is higher than that of solids. This is due to the fact that in the liquid state, particles move freely and have greater space between each other as compared to particles in the solid state.

Sublimation is the transition of a substance from the solid phase to the gas phase without passing through an intermediate liquid phase.

Triple Point is the temperature and pressure at which solid, liquid, and vapour phases of a particular substance coexist in equilibrium. A specific case of phase equilibrium. e.g.The triple point for water is at 0.01^o Celsius at 4.56 mm Hg.

In water, evaporation takes place the slowest. 

Separation funnel

Adding salt (sodium chloride, NaCl) to water elevates its boiling point through boiling point elevation, a colligative property of solutions. The salt ions (Na+ and Cl-) disrupt the formation of water vapor at the surface, requiring more energy (higher temperature) for the water to boil. The boiling point increases proportionally to the concentration of dissolved particles. Sugar also raises boiling point but salt is the classic example. Oil doesn't dissolve in water, and chlorine is a gas.

Butter is not converted into a vapour state without passing through a liquid state.

According to the Stefan-Boltzmann law and Kirchhoff's radiation law, a black surface is a nearly perfect emitter and absorber of thermal radiation (good black body). A rough surface has greater effective surface area for emission compared to a polished one. Therefore, a black and rough surface radiates heat most rapidly. Polished surfaces are poor emitters, while white surfaces reflect more radiation than they emit. This is why radiator fins are often black and rough.

 Hydrogen and helium, the lightest two gases, weigh so little that helium balloons and hydrogen dirigibles are able to float in the atmosphere.