Important Questions (1 mark): Matter in our Surroundings - UPSC MCQ

K = °C + 273, 

25°C = 273 + 25 = 298K.

So, temperature of 25°C is equal to 298K.

With increase in temperature, inter-particles forces decreases. As the melting point of solid A is less than Solid B. Solid B has more inter-particle forces of attraction. Higher the melting point more the inter-particle force.

An endothermic process is any process which requires or absorbs energy from its surroundings, usually in the form of heat. It may be a chemical process, such as dissolving ammonium nitrate in water, or a physical process, such as the melting of ice cubes. Insoluble heavy impurities involve the opposite of an endothermic process which is exothermic process one that absorbs energy in the form of heat.

Air is a mixture of gases. Two main constituent of air are Oxygen (21%) and Nitrogen (78%). Other gases includes carbon dioxide, helium, water vapour etc.

In Kelvin temperature, the symbol (^∘) is not used. Mercury is used in glass thermometers because it does not stick with glass and have shiny surface to viewed easily.

solid carbon dioxide is known as dry ice. The reduced evaporation is called humidity. Evaporation is increased by temperature. The liquefied gas increases pressure and reduces temperature.

The process of changing solid directly into gases without changing into liquid is called sublimation. In the substance given above only Iodine is a sublime substance.

Brass is a homogeneous mixture of copper and zinc.

Water can undergo a change in state upon heating and cooling. On heating above 100⁰C water change into gaseous state and on cooling below 0⁰C it changes into solid state.

Rate of diffusion in gases is high because they have large intermolecular space and they possess more kinetic energy than liquids and gases.

When the liquid starts boiling, the further heat energy which is supplied is absorbed as latent heat of vaporization by the liquid to change its state of matter.

At room temperature, sulfur dioxide is a nonflammable, colorless gas that is heavier than air. Its strong, pungent odor and irritating properties usually provide adequate warning of its presence.

When the pressure on the surface of a gas is increased. The particles of gases comes closer that increase the inter-particle force of attraction.

The characteristics of particles of matter are as follows:

1. Particles of matter have space between them

When we dissolve salt in water, it is observed that the particles of salt get evenly distributed in water. Also, it is observed that the presence of salt particles did not change the level of water in the beaker. This could be possible only if the particles of salt were accommodated in between the water particles. Thus, this clearly proves that space exists between water particles.

2. Particles of matter are in continuous motion

We know that there is a lot of space present between the particles of matter. Particles of matter are never at rest and keep moving continuously in these free spaces. The particles of matter move continuously and their speed increases with an increase in temperature.

3. Particles of matter attract each other

The particles of matter attract each other. However, this force of attraction varies from matter to matter.

Evaporation is a surface phenomenon as takes place only on the surface of liquid but boiling is a bulk phenomenon. The rate of diffusion of gases varies inversely as the square root of their densities.

The temperature of the liquid becomes constant once it starts boiling. The heat is used to change the state of matter. The pressure of air at the sea level is 760mm of Hg. So, statement A is correct only.

In the different sets of substance given above, salt, sugar and chalk are solid under ordinary temperature. As Mercury, water and oxygen and nitrogen are not solid.

The process of changing solids into gases without changing into liquid state or gases directly into solid is called sublimation.

Before its development as a surgical anesthetic, ether was used throughout the history of medicine, including as a treatment for ailments such as scurvy or pulmonary inflammation. A pleasant-smelling, colorless and highly flammable liquid, ether can be vaporized into a gas that numbs pain but leaves patients conscious.

Impure sample of naphthalene can be purified by sublimation process. During this process, naphthalene being sublime changes into vapours leaving behind impurities. Vapour can be cooled by condensation.

State of matter can be changed by changing temperature and pressure. A gas can be liquefied by increasing the pressure and reducing the temperature to brings the particle close to each other.

A liquid is kept in an open china dish. The evaporation of the liquid can be accelerated by keeping the dish in the open, by blowing air into the liquid or by keeping the dish under a running fan. Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance.

The process of changing liquid into gases from its upper surface at all temperature is called evaporation. Rate of evaporation increase with increase in temperature, surface area and wind speed.

Boiling is a physical process. When boiling takes place, particles in the substance vibrate more and of weak intermolecular bonds are broken in order for the substance being heated to move into the gaseous phase. Covalent bonds are not broken when boiling occurs. This means that no chemical reaction has taken place. The ratio in which the atoms are bonded together in a substance remains constant.

Hydrogen as a fuel in Sun. The source of Sun's incessant energy is hydrogen which is continuously converting to helium through nuclear fusion reaction releasing energy.