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The correct answer is curve (a) may represent the plot

The correct answer is (a) (c) 

(a) the maximum intensity of radiation will be near the frequency 2v₀

(c) the total energy emitted will increase by a factor of 16.

(i) Mass remains the same on heating. 

(ii) Internal diameter increases. 

(iii) External diameter increases. 

(iv) Density decreases.

When the bottle is heated, air in it expands and escapes the water in the form of bubbles.

The correct answer is (d) T⁴₂ - T⁴₁

False Temperature of a liquid rises during boiling or vaporization.

True Boiling is a rapid phenomenon.

True All molecules of a liquid take part in boiling.

During boiling or vaporization, all molecules take part

Two rods A and B of the same metal, but of length 1 m and 2 m respectively, are heated from 0°C to 100°C. Then the rod B elongates more than the rod A

BOILING: “The change of liquid to vapors on heating at a constant temperature is called BOILING” 

K.E = 1/2 Mv²: more the speed of molecules more is the kinetic energy. Heating of the liquid increases the average K.E. of liquid molecules and molecules acquire sufficient K.E. needed to overcome the force of attraction of other molecules. These molecules start leaving the liquid not only at the surface but also near the walls of the containing vessel and bubbles are seen on the walls of the vessel. This causes the agitation in the whole of the liquid and this is called boiling.

When liquid is the heated formation of vapors takes place which appears in the form of bubbles.

(c) Gas will expand more as the inter-molecular force of attraction in gas molecules is least and K.E. is maximum.

No, all the molecules of the liquid do not take part in evaporation only those molecules near the surface of liquid which acquire sufficient Kinetic energy (Threshold velocity) escape as they overcome attractive forces of other molecules. Then other molecules come to the surface of the liquid and acquire more K.E. and escape the surface. This continues until all the liquid evaporates.

The expansion of a substance on heating is called the thermal expansion of the substance.

False Evaporation is rapid on a wet day.

True Evaporation takes place only from the surface of liquid.

The rate of evaporation of a liquid increases when : air is blown above the surface of liquid

For changing liquid into vapors heat is needed this heat is taken from the container or surroundings and temperature of container or body itself fall and cooling are produced.

MATTER: Anything around us is a matter. “Anything that has mass, occupies volume and can be felt by our senses.” 

It is composed of‘molecules’.

all the above three factors.

A given volume of alcohol and the same volume of water are heated from the room temperature to the same temperature then. alcohol expands more than water.

A little space is left between two rails on a railway track.

In summer when the temperature increases considerably the bridge made of metal expands and rollers slide to allow for expansion otherwise the bridge may break the pillar.

Substances when heated expand. Their density [ m/v] decrease. But in the case of water: When water is heated from 0°C to 4°C it CONTRACT and density INCREASE, heating water above 4°C starts expanding and density of water decrease. 

This means water has maximum density at 4°C. This is called the anomalous behavior of water.

False Kerosene contracts on heating.

Density = Mass / Volume 

In case of SOLIDS, when the temperature is increased, increase in volume is very small and a decrease in density is not appreciable. In case of LIQUIDS and GASES, as the temperature increases, volume increases by an appreciable amount and therefore decrease in their density is quite considerable.

Substances expand on heating. 

But WATER—CONTRACTS with heated from 0°C to 4°C. After that i.e. above 4°C water starts expanding.

True Solids expand the least and gases expand the most on being heated.

False All solids expand by the same amount when heated to the same rise in temperature.

Iron, water expand on heating.

True Telephone wires are kept tight between the two poles in winter.

(a) Metals expand on heating (in summer) and contract on cooling (in winter). Therefore while putting up the wires between two poles, care is taken that they are kept tight while laying them in winter as they sag in summer due to expansion. 

(b) Iron rims are made slightly smaller in diameter than the wooden wheel and on heating, wheel expands and can easily slip over the wooden wheel and on cooling the rim contracts and MAKES A TIGHT FIT OVER the wooden wheel.

(c) In summer due to a considerable rise in temperature, the gaps allow for the expansion of rails, otherwise, the rail will bend sideways. 

(d) By pouring hot water on the neck of the bottle, the neck expands and stuck glass stopper can easily be removed. 

(e) In summer when the temperature rises small pieces of cement expand and to allow expansion gaps are left between small pieces.

The correct answer is (c) (d) 

(c) reflect radiation 

(d) refract radiation.

Two rods A and B of the same metal, same length, but one solid and the other hollow, are heated to the same rise in temperature. Then both the rods A and B expand the same.

The correct answer is 

(a) Both will emit equal amount of radiation per unit time in the biginning. 

(b) Both will absorb equal amount of radiation from the surrounding in the biginning. 

A = 12cm² = 12 × 10^–4m² T = 20°C = 293K
e = 0.8 σ = 6 × 10^–8w/m²-k⁴

Q/t = AeσT⁴ = 12 × 10^–4 0.8 × 6 × 10^–8 (293)⁴ = 4.245 × 1012 × 10^–13 = 0.4245 ≈ 0.42

On heating, the ball expands and increases in size and cannot pass the ring when left on it. As the ball cools, it contracts, size becomes less than a ring and passes the ring.

When a solid is heated, it expands in all directions. The volume of a cube also increases. 

Let V₀ be the volume of cube of side L₀ at 0°C. i.e. V₀ = L₃₀ – V 

When temperature increases to t°C each side increases to V_t 

∴ V_t = L_t³ 

Increase in volume = (V_t — V₀) [L_t³ — L₀³] 

Increase in temperature = (t — O)°C = t°C

Factors on which increase in length of a rod depend when heated are: 

(1) Length of rod L. Increase in length is directly proportional to original length. 

(2) Temperature of rod. It is directly proportional to increase in temperature. 

(3) Nature of material of rod. 

If L₁ is the original length of the rod at t ₁ °C and on heating to t₂ °C its length becomes L ₂. 

∴ Increase in length of rod = ( L ₂ – L ₁ ) and increase in temperature ( t₂ – t₁ ) 

∴ [L₂ – L₁] ∝ L₁(t₂ – t₁ ) 

But the increase in length of rod does not depend on whether the rod is solid or hollow.

THREE FACTORS ARE: 

(i) Original area of plate A0. 

(ii) Rise in temperature t. 

(iii) Nature of material of plate.

(a) Boiling occurs at a fixed temperature. 

(b) Evaporation takes place at all temperature. 

(c) The molecules of liquid absorb heat from surroundings in evaporation. 

(d) Heat is absorbed during boiling. 

(e) Cooling is produced in evaporation. 

(f) A longer rod expands more than a shorter rod on being heated to the same temperature. 

(g) Liquids expand more than the solids. 

(h) Gases expand more than the liquids. 

(i) Alcohol expands more than water. 

(j) Iron expands less than copper.

EVAPORATION: “The change of liquid into its vapors at all temperature from its surface is called evaporation.” 

EXPLANATION OF EVAPORATION on the bases of molecular motion: Molecules of liquid have more spaces, the less molecular force of attraction and more K.E. than molecules of solids and can move throughout the liquid. While moving they can not escape the surface as they are being pulled inside by other molecules as there are no molecules above the surface. But when some molecules acquire sufficient K.E. (Threshold velocity), they overcome the ATTRACTIVE FORCES of other molecules and escape into the open space above the liquid. These escaping molecules from the vapor of the liquid and the process called Evaporation continues till all the liquid evaporates.

DISTINCTION BETWEEN LIQUID AND VAPOUR ON THE BASES OF:

THREE STATES OF MATTER:

 (i) SOLID (ii) LIQUID (iii) GASEOUS 

DISTINCTION BETWEEN THREE STATES ON THE BASES OF. 

(i) VOLUME: 

SOLIDS: have least volume. 

LIQUIDS: have definite volume. 

GASES: have maximum volume. 

(ii) SHAPE: 

SOLDIS: Have a definite shape. 

LIQUIDS: Have no definite shape. 

GASES: Have no definite shape.