Question 1

Question 10Draw a labelled schematic diagram representing the terms - (a) to (e) involved in the inter-conversion of matter.

Accepted Answer

Below labelled diagram represents the different terms involved in the inter-conversion of matter:

Question 2

Question 5What happens to water if:(a) it is kept in a deep freezer?(b) it is heated?Explain the phenomenon of change of state of water.

Accepted Answer

(a) When water is kept in a deep freezer, it gets cooled and changes into ice at 0°C.Water →freezedeep\xrightarrow[	ext{freeze}]{	ext{deep}}deepfreeze​ ice (0°C)(b) When water is heated it changes into steam at 100°C.Water →heating\xrightarrow{	ext{heating}}heating​ steam (100°C)Phenomenon of change of state of water — In ordinary conditions water is in liquid state. When it is kept in deep freezer, it changes into ice at 0°C. But ice changes back into liquid state when ice is kept at room temperature.On heating water, it changes into steam at 100°C. On cooling steam changes back into liquid water. During the change of state from liquid to solid or liquid to gas there is no change in the chemical composition of water during these change of states.

Question 3

Question 6(a) State the law of conservation of mass.(b) What do you observe when barium chloride solution is mixed with sodium sulphate solution?

Accepted Answer

(a) The law of conservation of mass states that matter can neither be created nor be destroyed in a chemical reaction. Only it can be changed from one form to another during the reaction process.(b) When barium chloride solution is mixed with sodium sulphate solution, a white insoluble precipitate of barium sulphate is formed along with a solution of sodium chloride.BaCl2 + Na2SO4 ⟶ 2NaCl + BaSO4↓On weighing the apparatus before and after the reactions it is found that:Total mass of the apparatus + reactants = Total mass of the apparatus + productsThis observation verifies the law of conservation of mass.

Question 4

Question 7Give reasons:(a) A gas can fill the whole vessel in which it is enclosed.(b) Solids cannot be compressed.(c) Liquids can flow.(d) When magnesium is burnt in air, there is an increase in mass after the reaction.

Accepted Answer

(a) The particles of gases lie far apart from each other and the intermolecular spaces are therefore very large. The intermolecular forces of attraction are so weak that the particles are free to move and they have high kinetic energy, so they fill the whole vessel in which it is enclosed.(b) In solids, the particles are closely packed. There is a strong force of attraction between the particles and the intermolecular space is almost negligible. The molecules are therefore not free to move. They only vibrate about their mean positions. This makes solids difficult to compress.(c) In liquids the molecules are loosely packed and the intermolecular forces of attraction is not so strong as solids. The intermolecular space is larger and kinetic energy is more as compared to solids. The particles can move freely and randomly which makes the liquids to flow.(d) When magnesium is burnt in air, it forms magnesium oxide. The mass of magnesium oxide is found to be more than the mass of magnesium because the mass of oxygen used is not taken into consideration. If that is considered the total mass of the reactants and the products are found to be almost equal.2Mg + O2 →heat\xrightarrow{	ext{heat}}heat​ 2MgO

Question 5

Question 8Fill in the blanks:(a) The change of a solid into a liquid is called ............... .(b) The process in which a solid directly changes into gas is called ............... .(c) The change of water vapour into water is called ............... .(d) The temperature at which a liquid starts changing into its vapour state is ............... .

Accepted Answer

(a) Melting(b) Sublimation(c) Condensation(d) Boiling point

Question 6

Question 9Give two examples for each of the following:(a) The substances which sublime.(b) The substances which do not change their state on heating.

Accepted Answer

(a) Camphor, Ammonium Chloride.(b) Oxygen, Helium.

Question 7

Question 10Define:(a) Diffusion(b) Brownian motion

Accepted Answer

(a) The intermixing of two or more substances due to the motion of their particles in order to get a uniform mixture is called diffusion.(b) The haphazard, random motion of suspended particles on the surface of a liquid or in air is called Brownian motion.

Question 8

Question 11When sodium chloride is added to a definite volume of water and stirred well, a solution is formed, but there is no increase in the level of water. Why?

Accepted Answer

There are some intermolecular spaces between the particles of water. When sodium chloride is added into water and stirred, the particles of sodium chloride occupy the intermolecular spaces present in water particles and gets accommodated so there is no increase in the level of water.

Question 9

Question 12What do you observe when a gas jar which appears empty is inverted over a gas jar containing Bromine vapours? Name the phenomenon.

Accepted Answer

Reddish brown vapours of bromine spread out from the gas jar into the empty jar. This phenomenon is called diffusion.

Question 10

Question 13Why can a piece of chalk be broken easily into smaller pieces while a coal piece cannot be broken easily?

Accepted Answer

The magnitude of intermolecular force of attraction between the molecules of coal is much higher than that between the molecules of chalk. Hence, a piece of chalk can be broken easily into smaller pieces while a coal piece cannot be broken easily.

Question 11

Question 13State the 'law of conservation of mass'. State the main points of Landolt's experiment for experimental evidence of the law. State the limitations of the law.

Accepted Answer

Law of conservation of massLaw of conservation of mass states that whenever a chemical change takes place, the total mass of the reacting substances is exactly equal to the total mass of the products, [provided masses are measured under similar conditions].Main points of Landolt's experimentIn an 'H' shaped tube as shown in the figure, Landolt introduced a solution of sodium chloride [NaCl] and silver nitrate [AgNO3] in the limbs of the tube and sealed it and weighed it.The solutions were mixed by shaking to obtain a white precipitate of silver chloride.The tube was again weighed after the experiment.Result : Weight of H tube + reactants = Weight of H tube + products.Hence, total mass of reactants = total mass of productsLimitations of the lawChemical energy stored up in the reactants is released in the form of heat and light.Hence, mass is converted to energy and thus mass and energy are to be considered together.Hence, a very slight error in the experiment was observed.

Question 12

Question 3Complete the statements by filling the blanks with the correct word from the bracket.In naphthalene, the inter-particle attraction is ............... [high/low].The law of conservation of mass, is strictly valid if mass and ............... [energy/volume] are considered together.When inter-particle space increases, the inter-particle attractive force ............... [decreases/increases]Kinetic energy of molecules in helium is ............... [large/very large] compared to the kinetic energy of molecules in water.Conversion of vapour [or gas] into a liquid is termed ............... [liquefaction/vaporization].

Accepted Answer

In naphthalene, the inter-particle attraction is low.The law of conservation of mass, is strictly valid if mass and energy are considered together.When inter-particle space increases, the inter-particle attractive force decreases.Kinetic energy of molecules in helium is very large compared to the kinetic energy of molecules in water.Conversion of vapour [or gas] into a liquid is termed liquefaction.

Question 13

Question 4Give reasons for the following:Particles of matter possess energy called kinetic energy.Solids cannot be compressed, but gases are highly compressible.Kinetic energy of molecules of gases is very large & of solids, the least.On heating a sublimable solid, the molecules break free & escape from surface of the solid directly into vapour.Particles of matter move more rapidly on application of heat.

Accepted Answer

Particles of matter are in continuous motion and hence possess energy called kinetic energy.As inter-particle space in solids is minimum, hence, they cannot be compressed. Gases on the other hand, have very large inter-particle space, hence are highly compressible.As inter-particle space in gases is very large and inter-particle attraction is negligible, hence they are in random motion all the time and posses high kinetic energy whereas solids have minimum inter-particle space, maximum inter-particle attraction and they can move only about their own position. Hence they have least kinetic energy.Sublimable solid have very low force of attraction between their particles. On heating, these solids overcome the inter-particle attraction and the molecules break free & escape from surface of the solid directly into vapour.Application of heat increases the kinetic energy of the particles which then move more randomly.

Matter

Change of state of matter - interconversion

Exercise

Law of conservation of mass

Objective Type Questions