Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.

Anything that occupies space and has mass is called matter. Matter can exist in three physical states—solid, liquid, and gaseous. Chair and almond are forms of matter in the solid state. Cold drink is a liquid state of matter. Air is a gaseous state of matter. Note: The sense of smell is not matter. However, the smell or odour of a substance is classified as matter. The smell of any substance (say, perfume) can be classified as matter. This is because, perfume is in liquid state inside the bottle. It comes out in the form of tiny droplets. These droplets of perfume are matter and spread out in the atmosphere to create a sense of smell. This smell can be detected by our olfactory system.

Solution:
Since hot sizzling food has temperature higher than cold food and at higher temperature diffusion rate (movement) of particles is very fast due to this the smell of hot sizzling reaches us from several metres away.

Solution:
If diver has ability to cut through water in a swimming pool then it shows that the particles of matter have a kind of force working between them. Because of this force the particles of matter remain together till some external force is applied.

Solution:
The characteristics of particles of matter are as follows: i) particles of matter have gap between them. ii) particles of matter are in continuous motion iii) particles of matter have an attraction force between them to keep them together.

Solution:
Arranging substances in their increasing order of densities: Air < exhaust from chimneys < cotton < water < honey < chalk < iron.

Solution:
(a) The differences in the characteristics of states of matter are given in the following table. (b) Rigidity: It is the property of matter to maintain its shape even if external forces work and the solids show this property. Compressibility: It is the property of matter to allow compression under high pressure and the gases show this property. Fluidity: It is the property of a substance to easily flow and allow change in its shape under external forces and this property is exhibited by both liquids and gases. Filling a gas container: Gases can be compressed easily hence they can be filled within a vessel at high pressure. This property of gases allows their convenient filling into a small container or cylinder and that also in a large volume. It also allows their easy transport from one place to the other e.g. CNG. Shape: According to the type of matter shape differs depending upon location of particles like Solids have definite shape while Liquids acquire the shape of their container and gases as such don’t have any shape. Kinetic energy: It is the kind of energy present in an object when it is under motion as the particles of that object/matter are continuously moving therefore matter has kinetic energy. However greater is the movement more will be the kinetic energy and vice a versa i.e. solid < liquid < gas Density:Mass per unit volume of a substance /matter is known as its density i.e. density = mass/volume

(a) A gas fills completely the vessel in which it is kept.
(b) A gas exerts pressure on the walls of the container.
(c) A wooden table should be called a solid.
(d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.

(a) Since the attraction force between particles of a gas is negligible i.e. extremely less hence particles freely move/flow in all possible directions as a result gas fills completely the vessel in which it is kept.
(b) Freely moving particles of gas hit the walls of its container continuously and randomly therefore such random and erratic motion of gas particles exerts pressure on the walls of the container.
(c) A wooden table particle is quite rigid, have a fixed location and also possess a definite shape and volume. Due to all these properties, we should call a wooden table a solid substance.
(d) Air is a mixture of gases and since particles of gas are far apart so same is true for air therefore, we can easily move our hand in air. But a solid block of wood is hard and rigid that resists any change in location of its particles hence we need a karate expert in case of a solid block of wood.

Solution:
The mass per unit volume of a substance is called density (density = mass/volume). As the volume of a substance increases, its density decreases. Though ice is a solid, but it has a cage like structure hence there are large number of empty spaces between its particles. These spaces are larger as compared to the spaces present between the particles of water. Thus, for a given mass of water, volume of ice is greater than that of water. Hence, the density of ice is less than that of water. A substance with lower density than water can float on water. Therefore, ice floats on water.

Solution:

(a) 300 K = (300 − 273)°C = 27°C
(b)573 K = (573 − 273)°C = 300°C

Solution:

(a) Water at 250°C exists in gaseous state.
(b) At 100°C, water can exist in both liquid and gaseous form. At this temperature, after getting the heat equal to the latent heat of vaporization, water starts changing from liquid state to gaseous state.

Solution:
During a change of state, the temperature remains constant. This is because all the heat supplied to increase the temperature is utilised in changing the state by overcoming the forces of attraction between the particles. This heat is called the latent heat. Latent heat does not contribute in increasing the temperature of the substance.

Solution:
If we decrease temperature and increasing pressure we can liquefy the atmospheric gases.

Solution:
When a liquid evaporates, the particles of the liquid absorb energy from the surroundings to compensate the loss of energy during evaporation. This makes the surroundings cool. In a desert cooler, the water inside it is made to evaporate. This leads to absorption of energy from the surroundings, thereby cooling the surroundings.
Again, we know that evaporation depends on the amount of water vapour present in air (humidity). If the amount of water vapour present in air is less, then evaporation is more. On a hot dry day, the amount of water vapour present in air is less. Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more. That is why a desert cooler cools better on a hot dry day.

Solution:
The earthen pot is porous with lot of pores on it, the water oozes out through these pores and the water gets evaporated at the surface of the pot thereby causing cooling effect. This makes the pot cold and the water inside the pot cools by this process.

Solution:
Acetone, petrol or perfume evaporate when they come into contact with air. The evaporation causes cooling sensation in our hands.

Solution:
Saucer has a bigger surface area as compared to cup. Since evaporation is a surface phenomenon, by using a saucer instead of cup we are increasing the surface are for evaporation to occur. Faster evaporation of particles of tea or milk allows cooling and taking a sip becomes easier.

Solution:
We should wear light coloured cotton clothes in summer. Light colour because it reflects heat. Cotton clothes because it has pores in it, which absorbs sweat and allows the sweat to evaporate faster thereby giving cooling effect.

Solution:

(a) 293K = (293 – 273)°C = 20°C
(b) 470K = (470 – 273)°C = 197°C

Solution:

(a) 25°C = (25+273)K = 298K
(b) 373°C = (373+273)K = 646K

Solution:

(a) At room temperature, naphthalene balls undergo sublimation wherein they directly get converted from a solid to a gaseous state without having to undergo the intermediate state, i.e., the liquid state.
(b) Molecules of air move at a higher speed and have large intermolecular spaces. Perfumes comprise substances that are volatile, which scatter quickly in air, becoming less concentrated over a distance. Hence, we are able to smell perfume sitting several metres away.

Solution:

Oxygen (gas) < water (liquid) < sugar (solid)

Solution:

(a) At 25°C, the water will be in liquid form (normal room temperature)
(b) At 0°C, the water is at its freezing point, hence both solid and liquid phases are observed.
(c) At 100°C, the water is at its boiling point, hence both liquid and gaseous states of water (water vapour) are observed.

Solution:

(a) Water persists as a liquid at room temperature since its melting point is lower than room temperature and its boiling point (100o C) is higher.
Similarly,
(i). A fixed volume is occupied by a fixed mass of water.
(ii). At room temperature, water does not have a fixed shape and flows to fit the container’s shape.
As a result, water is a liquid at room temperature.
(b) Because its melting and boiling points are above room temperature, an iron almirah is a solid at room temperature. In the same way,
(i) An iron almirah is rigid and has a predetermined shape.
(ii) Metals have a relatively high density.
As a result, at room temperature, iron almirah is a solid.

Solution:

At 273 K, ice will absorb heat energy or latent heat from the medium to overcome fusion and transform into water. As a result, ice has a greater cooling impact than water at the same temperature since water does not absorb the excess heat from the medium.

Solution:

Steam produces severe burns. It is because it is an exothermic reaction that releases a high amount of heat which it had consumed during vaporization.

Solution:

(A) Solid to Liquid → Melting (or) fusion (or) liquefaction
(B) Liquid to Gas → Evaporation (or) vaporization
(C) Gas to liquid → Condensation
(D) Liquid to Solid → Solidification
(E) Solid to Gas → Sublimation
(F) Gas to Solid → solidification