Explore topic-wise InterviewSolutions in Current Affairs.

Atoms or molecules make up matter or matter is composed of atoms/molecules.

Coal gas is a gas obtained during the processing of coal to get coke. 

Uses: 

1. It is used in lighting. 

2. It is used as fuel in many industries.

When heated in air, coal burns and produces mainly carbon dioxide gas. Coal can be processed in industry to get some useful products such as coke, coal tar and coal gas. Coal is used as a fuel in industries and was used to cook food. It was used in railway engines to produce steam to run the engine. It is used in thermal power plants to produce electricity.

CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). It can be used as a fuel in homes and factories. It is also used as a starting material for the manufacture of a number of chemicals and fertilizers.

India has huge reserves of natural gas. It has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta. It is advantageous to use CNG as a fuel because it is less polluting than petrol. It is a clean burning fuel. It produces 45% less hydrocarbons than petrol. The great advantage of CNG is that it can be used as fuel in homes and factories where it can be supplied through pipes.

LPG stands for liquified Petroleum Gas. It is used as fuel for home and industry. Advantages of using LPG as a fuel is that it is non-toxic and reduces the interior pollution by 90% as compared to other fuels such as coal or wood. The carbon dioxide emissions are very low. It is an economical fuel source. It burns very efficiently, with very low combustion emissions and does not create black smoke.

(i) The measure of a right angle is 90°

(ii) The measure of a straight angle is 180°

(a) An angle who se measure is greater than that of a right angle is Acute angle 

(b) An angle whose measure is greater than that of a right angle is obtuse 

(c) An angle Whose measure is the sum of the measures of two right angles is Straight angle 

(d) When the sum of the measure of two angles is that of a right angle, then each one of them is Acute 

(e) When the sum of the measures of two angles is that of a straight angle and it one of them is acute then the other should be obtuse angle

(a) A cute angle as its measure is less than 90°

(b) Obtuse angle as its measure is more than 90° but less than 180°

(c) Right angle as its measure is 90°

(d) Reflex angle as its measure is more than 180° but lass than 360°

(e) Straight angle as its measure is 180°

(f) Acute angle as its measure is less than 90°

Coal is black in colour and hard as stone. It is one of the fuels used to cook food. Earlier it was used in railway engines to produce steam to run the engine. It is used as fuel in thermal power plants to produce electricity and in various other industries.

Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea).

Many useful substances are obtained from petroleum and natural gas. These are termed as ‘Petrochemicals’. These are used in the manufacture of detergents, fibres such as polyester, nylon, acrylic etc., polythene and other man-made plastics.

Hydrogen gas obtained from natural gas, is used in the production of fertilisers such as urea. Due to its great commercial importance, petroleum is also called ‘black gold’.

No, their formation is very slow process and conditions for their formation cannot be created in the laboratory.

At Makum in Assam, in 1867, oil was stuck in India. Oil is found in Assam, Gujarat, Mumbai High and in the river basins of Godavari and Krishna.

The world’s first oil well was drilled in Pennsylvania, USA, in 1859

Hint: Oil is lighter than water hence floats over it.

The characteristic of matter illustrated by this observation is that the particles of matter have spaces between them.

Characteristics of solid states are : 

(a) Have definite shape. 

(b) Have distinct boundaries. 

(c) Have rigidity and incompressibility. 

(d) Have definite volume.

On the cooling the energy of gas particle decreases, and so the moment of the particle is slowed down. The particles also come much closer to each other leading to the intermolecular force of attraction. This causes the gas to contract.

There is a fourth state of matter- “plasma”. Plasma state is mainly responsible for the glow of the sun and the stars.

The process in which a solid substance changes into a liquid on heating is called melting.

Water is change upon heating or cooling.

➢ Matter consists of small particles separated by small distances.

➢ In the solid state the inter particle distances are very small.

➢ In the liquid state the inter particles distances are a little more than in solids.

➢ In the gaseous state the inter particle distances are he largest when compared to liquids or solids.

➢ It can thus be seen that when pressure is exerted on matter, the effect of the pressure on solids will be negligible as the particles are very close together.

➢ The effect of pressure in liquids will be small.

➢ The effect of pressure on gases will be the largest as the inter particle distances are large.

➢ Thus, when ever pressure is exerted on gases, the particles move closer together.

➢ As the particles move closer together, the attractive forces between the particles increases.

➢ This increase in attractive forces helps in the change of state of the gas. If the pressure exerted is sufficiently large he attractive forces increase to such an extent that the physical state changes from gaseous to liquid.

➢ The reverse can be expected to happen if the pressure on a gas is deceased.

The molecules of water have more energy than that of ice. When solidified, the water molecules must lose energy to the surroundings to form ice. So heat is evolved in the conversion of water to ice.

(a) When sugar dissolves in water, its tiny particles break off from the solid sugar crystals.

(b) the sugar particles go into the spaces between the particles of water and mix with them (to form sugar solution).

(c) The dissolution of sugar in water tells us that:

i) The matter (here sugar and water) is made up of small particles.

ii) The particles of matter (here water) have spaces between them

It is a liquid.

(a) Decrease in pressure; Increase in temperature

(a) The adjacent angles of a table top

The adjacent edge of a table top are perpendicular to each other.

(b) The line of a railway track

The lines of a railway track are parallel to each other.

(c) The line segments forming the letter ‘L’

The line segments forming the letter ‘L’ are perpendicular to each other.

(d) The letter V.

The sides of letter V are inclined at some a cute angle on each other

Hence (a) and (c) are the models for perpendicular lines.

(a) Yes, As CE = EG = 2 units

(b) Yes, PE bisects CG since CE = EG

(c) DF and BH

(d) (i) True, As length of AC and FG are of 2 units and 1 unit respectively

(ii) True, As both have 1 unit length

(iii) True, As the length of BC and EH are of 1 unit and 3 units respectively.

(ii) Latent heat

(a) The measure of an acute angle <90°
True

(b) The measure of an obtuse angle <90° False 

(c) The measure of reflex angle > 180°
True

(d) The measure of one complete revolution = 360°
True

(e) If m∠A = 53° and m∠B = 35°, then m∠A > m∠B.
True

Salt when dissolves in water the tiny particles occupy the spaces between the water particles and mix with them, thus gives a taste to water. There won’t be any increase in volume of water.

It is quantity of heat in Joules which is required to convert unit mass or 1 kg solid into liquid form without rise in temperature.

It has been found by experiments that 3.34 x10⁵ J of heat is required to convert 1 kg of ice in water at same temperature (0°C).

So, latent heat of fusion of ice is 3.34 x10⁵ J/ Kg.

Different substances have different Latent Heat of Fusion.

➢ The process in which a solid substance changes into a liquid on heating is called melting (or fusion).

➢ The point of temperature at which solid melts and changes into a liquid at atmospheric pressure is called melting of the substance.

➢ When a solid substance is heated the heat energy makes its particles vibrate more vigorously. At the melting point the particles of a solid have sufficient kinetic energy to overcome the strong forces of attraction holding them in fixed positions and break to form small groups of particles. And the solid melts to form a liquid.

➢ Higher the melting point of a solid substance, greater will be the force of attraction between its particles. For example, the melting point of iron metal is very high (1535°C) which tells us that the force of attraction between the particles of iron is very strong.

There are two types of latent heat:

i) Latent heat of fusion

ii) Latent heat of vaporization

➢ The process of changing a gas (or vapour) to a liquid by cooling is called condensation where a gas is cooled enough.

➢ So, when steam (or water vapour) changes into water on cooling, it is called condensation of steam (or condensation of water vapour).

➢ It is the reverse of vaporization. (Boiling)

(a) In the interior of ∠DOE

A

(b) In the exterior of ∠EOF

C.A.D

(c) On ∠EOF

B.E.D.F

∠BAD, ∠ADC, ∠DCB, ∠CBA.

\(\vec{AB}, \vec{BC},\vec{CD}, \vec{CB},\vec{DC},\vec{AD},\vec{DA},\vec{AC},\vec{CA},\vec{BD}\)

(a) \(\vec{AE}\)

(b) \(\vec{AE}\)

(c) \(\vec{OC}\)

(d) \(\vec{OC}\)  and \(\vec{AE}\) , \(\vec{AE}\) and \(\vec{EF}\)

(a) infinite number of lines can pass through a single point.

(b) Only one line can pass through two given points

(a) its centre

O

(b) a radius

\(\bar{OA}\)

(c) a diameter

\(\vec{AB}\)

(d) a sector

COA

(e) a segment

DE

(f) a point in its interior

O

(g) a point in its exterior

F

(h) an arc

\(\vec{AC}\)

(a) Q, M, O, N, P are points on the line \(\vec{MN}\) - True

(b) M, O, N are points on a line segments \(\vec{MN}\) - True

(c) M and N are end points of line segment \(\vec{MN}\) - True

(d) O and N are end points of line segment \(\vec{OP}\) - True

(e) M is one of the end points of line segment \(\vec{QC}\)  – False

(f) M is point on ray \(\vec{OP}\)  – False

g) Ray \(\vec{OP}\) is different from ray \(\vec{QP}\)  – True

(h) Ray \(\vec{OP}\) same as ray \(\vec{OM}\)  – True

(i) Ray \(\vec{OM}\) is net opposite to ray \(\vec{OP}\)  – True

(j) O is net an initial point of \(\vec{OP}\)  – False

(k) N is the initial point of \(\vec{NP}\) and \(\vec{NM}\)  – True

(a) Yes, the diameter is the longest possible chord of the circle

(b) No.

(a) the centre of circle

O

(b) three radii

\(\bar{OA},\bar{OB},\bar{OC}\)

(c) a diameter

\(\bar{AC}\)

(d) a chord

\(\bar{ED}\)

(e) a segment

O.P

(f) a sector

Q

(g) a segment

AOB (Shaded region)

(h) a segment

DE (Shaded region)

➢ The process in which a liquid substance changes into a gas rapidly on heating is called boiling

➢ The point of temperature at which a liquid boils and changes rapidly into a gas atmospheric pressure is known as boiling point of a liquid.

• The amount of heat in Joules which is required to convert unit mass or 1 kg liquid in vapours form without rise in temperature is known as latent heat of vaporization.

• It has been found by experiments that 22.5 x10⁵ joules of heat is required to change 1 kilogram of water (at its boiling point, 100°C) to steam at the same temperature of 100°C. so, the latent heat of vaporization of water is 22.5 x10⁵ joules per kilogram (or 22.5 x10⁵ J/kg).

• “If the liquid freezes to form a solid and steam condenses to form water, an equal amount of latent heat of fusion and vaporization respectively will be given out by the substance.”

• Different substances have different Latent Heat of vaporization.

(a) A square can be through of as a special rectangle.

In a rectangle all the interior angles are of the same measure i,e, 90° and the opposite side of the rectangle are of the same length where as in case of a square, all the interior angles are of 90° and all the sides are of the same length in other words, a rectangle with all sides equal becomes a square there, a square is a special rectangle.

(b) A rectangle can be through of as a special parallelogram.

Opposite sides of a parallelogram are parallel and equal in a rectangle, the opposite sides are parallel and equal also, all the interior angles of the rectangle are of the same Measure, i,e. 90°. in other words, a parallelogram with each angle a right angle becomes a rectangle Therefore a rectangle can be thought of as a specific parallelogram.

(c) A square can be through of as a special parallelogram.

All sides of a rhombus and a square are equal However, in case of a square, all interior angles are of 90° Measure. A rhombus with each angle a right angle becomes a square Therefore a square can be thought of as a special rhombus.

(d) Squares, rectangles, parallelograms are all quadrilaterals.
All are closed figure made of 4 line segments Therefore all these are quadrilaterals.

(e) Square is also a parallelogram. Opposite sides of a parallelogram are parallel and equal in a square, the opposite sides are parallel and the lengths of the four sides are equal Therefore a square can be thought 6 f as a special parallelogram.

(a) Two diameters of a circle win necessarily intersect True

They will along interest each other at the centre of the circle

(b) The centre of a circle is always in its interior.
True