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The correct option is B) Climate.

The average weather pattern taken over a long period, say 25 years or more, is called the climate of a place.

Heat energy.

Heat energy.

Conduction takes place, only when the conductor is in touch (contact) with the source of heat. The contact which transfers heat by any mode is called Thermal contact. Conduction doesn’t take place without thermal contact.

The material which helps in transfer of heat from one place to another is called a medium. Solid, liquid and gaseous substances act as medium for transfer of heat.

Heat is transferred by means of currents called convectional currents.

In liquids and gases heat is transmitted by mode of convection of heat.

Correct option is: c) Q/mΔT

Correct option is: B) 100° C

Procedure : 

Take a beaker of water, keep it on the burner and note the readings of thermometer for every two minutes. 

Observation : 

• We will notice that the temperature of the water rises continuously till it reaches 100° C. 
• Once it reaches 100° C the temperature remains same and a lot of bubbling on the surface takes place. This is called boiling of water. 

Explanation : 

• It happens due to when water is heated the solubility of gases it contains reduces. 
• As a result, bubbles of gas are formed in the liquid. 
• Evaporation of water molecules from the surrounding liquid occurs into these bubbles and they become filled with saturated vapour. 
• At a certain temperature, the pressure of the saturated vapour inside the bubbles becomes equal to the pressure exerted on the bubbles from the outside. 

Conclusion : 

• As a result, these bubbles rise rapidly to the surface and collapse at the surface releasing vapour present in bubbles into air at the surface. This process is called “boiling”. 
• This temperature is called ‘boiling temperature”.

Mercury is used in a thermometer because of the following properties.

1. There is a big difference between the freezing point and boiling point of mercury. Its freezing point is – 39° C and its boiling point is 357° C. 

2. It is shiny and can be easily seen. 

3. It does not stick to glass. 

4. It expands regularly and uniformly in all conditions.

Heat is a form of energy. Particles of matter (atoms, molecules, etc.) possess potential energy and kinetic energy. Total energy (potential energy + kinetic energy) of all particles of matter in a given sample is called it’s thermal energy. When two bodies at different temperatures are in thermal contact with each other, there is transfer of thermal energy from a body at higher temperature to a body at lower temperature. This energy in transfer is called heat. It is expressed in joule, calorie and erg.

Temperature is a quantitative measure of degree of hotness or coldness of a body. It is expressed in °C, °F or K (kelvin). Temperature determines the direction of energy transfer.

Thermometer is an instrument that measures the temperature of a system quantitatively.

The sensual property of water between 0°C to 4°C is called anomalous expansion i.e. water on cooling contracts up to 4°C and afterwards it starts expanding till it freezes into ice at 0° C.

Sometimes water enters into crevices of the rocks. When the temperature of the atmosphere falls below 4°C, water expands. Even when water freezes to form ice, there is increase in its volume. As there is no room for expansion, it exerts a tremendous pressure on the rocks which crack and break up into small pieces.

When a solid is heated, initially, its temperature increases. Here, the heat absorbed by the body (substance) is used in increasing the kinetic energy of the particles (atomic, molecules, etc.) of the body as well as for doing work against the forces of attraction between them. As the heating is continued, at a certain temperature (melting point), solid is converted into liquid. In this case, the temperature remains constant and the heat absorbed is used for weakening the bonds and conversion into liquid phase (liquid state). This heat is called the latent heat of fusion.

When a liquid is converted into the gaseous phase (gaseous state), at the boiling point, the heat absorbed is used for breaking the bonds between the atoms or molecules. This heat is called the latent heat of vaporization. Some solids, under certain conditions, are directly transformed into the gaseous phase. Here the heat is absorbed but the temperature remains constant. The absorbed heat is used for breaking the bonds between atoms or molecules. This heat is called the latent heat of sublimation.

In general, latent heat is the heat absorbed or given out by a substance during a change of state at constant temperature. In transformations from liquid to solid, gas to liquid and gas to solid, latent heat is given out by the body (substance).

(Note: change of state = change of phase)

Data : m₁ = 2kg, ΔT₁ = 20 °C – 0 °C

= 20 °C, c₁ = 1 kcal/kg·°C, L₁ (ice) = 80 kcal/kg,

L2 (vaporization of ammonia) = 341 cal/g = 341

kcal/kg, m₂ =?

Q₁ (heat lost by water) = m₁c₁ ΔT₁ + m₁L₁

= 2kg × 1 kcal/kg·°C × 20 °C + 2 kg × 80 kcal/kg

= 40 kcal + 160 kcal = 200 kcal

Q₂ (heat absorbed by ammonia) = m₂L₂

= m₂ × 34l kcal/kg

According to the principle of heat exchange, Q₁ = Q₂

∴ 200 kcal = m₂ × 341 kcal/kg

∴ m₂ = \(\frac{200}{341}\) kg = 0.5864 kg = 586.4 g

586.4 g of ammonia are to be evaporated.

In winter, air temperature is low. Hence, when an aeroplane flies, the vapour released by its engine condenses and forms white clouds. If the relative humidity of the air surrounding the plane is high, we see this white trail at the back of the plane for a long time before it disappears. If.the relative humidity is low, the white trail is short and disappears quickly. If the relative humidity is very low, there is no formation of the white trail.

Here, % relative humidity = \((\frac{60g}{100g})\) × 100% = 60%

At the dew point temperature, relative humidity is 100%.

The ratio of the actual mass of water vapour content in the air for a given volume and temperature to that required to make the same volume of air saturated with water vapour at the same temperature is called the relative humidity.

% Relative humidity = [the actual mass of water vapour content in the air for a given volume and temperature ÷ the mass of water vapour required to make the same volume of air saturated with water vapour at the same temperature] × 100%.

Correct Answer is: (a)

Let ρ₀, ρ₁ and ρ₂ be the densities of the liquid at temperatures 0, t₁ and t₂ respectively

To balance pressure, ρ₁l₁g = ρ₂l₂g

or (ρ₀/1 + γt₁) l₁ = (ρ₀/1 + γt₂) l₂.

Correct Answer is: (a, c)

(a) conductors

(d) All the above

(c) thermal energy

(1) Latent heat – Q = mL

(2) Specific heat capacity – cal/g·°C

(3) Heat absorbed or given out by a body when its temperature changes – Q = mc ΔT.

(d) All the above

Units of temperature: °C, °F and K (kelvin).

1. Heat transfer depends on the nature of the substance. 

2. Water has high specific heat capacity than that of cooking oil. 

3. A substance with high specific heat capacity absorbs a large quantity of heat.

4. Thus, it takes long time to heat up.

The SI unit of heat energy is joule.

The gas supply, Two times as much.

Units of energy: the erg, the joule, the calorie.

Heat is a form of energy in transit that is transferred from the body at a higher temperature to the body at a lower temperature.

For 1°C change in temperature, heat energy needed = 1 Calorie 

∴ For 5°C change in temperature heat energy needed = 5 Calories.