Temperature and heat MCQ Quiz - Objective Question with Answer for Temperature and heat - Download Free PDF

The correct answer is 2) 100°C.

Key Points

• The boiling point of water at standard atmospheric pressure (1 atm) is 100°C (212°F).
• Water boils when its vapor pressure equals the atmospheric pressure surrounding it.
• The boiling point can change with variations in atmospheric pressure; at higher altitudes, water boils at lower temperatures.
• At sea level, where the atmospheric pressure is approximately 101.3 kPa, water reaches its boiling point at 100°C.

Additional Information

• Vapor Pressure:
  • The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature.
• Elevation and Boiling Point:
  • At higher elevations, atmospheric pressure is lower, causing water to boil at temperatures lower than 100°C.
• Latent Heat of Vaporization:
  • The amount of heat required to convert a unit mass of a liquid into vapor without a temperature change.
• Phase Change:
  • The process of a substance changing from one state (liquid) to another (gas) at its boiling point.

Calculation:

625 = msΔT + mL

625 = m[125 × 300 + 2.5 × 10⁴]

625 = m[37500 + 25000]

625 = m[62500]

m = \(\frac{1}{100}\) kg

∴ M = 10 grams

Concept:

Relation between Celsius and Fahrenheit Scales:

• The Fahrenheit (°F) and Celsius (°C) scales are related by the following formula:
  • F = (9/5) × C + 32
• In this problem, we are looking for the temperature at which the Fahrenheit temperature is twice the Celsius temperature. Let the temperature in Celsius be C, and the temperature in Fahrenheit be F.
• We are given that F = 2 × C.

Calculation:

Let the temperature in Celsius be C and the temperature in Fahrenheit be F.

We know that the relation between Celsius and Fahrenheit is:

F = (9/5) × C + 32

Also, we are given that:

F = 2 × C

Now, substitute F = 2 × C in the equation:

2 × C = (9/5) × C + 32

Multiply both sides by 5 to eliminate the fraction:

10 × C = 9 × C + 160

Now, subtract 9 × C from both sides:

C = 160

So, the temperature on the Celsius scale is 160°C.

Now, calculate the corresponding temperature on the Fahrenheit scale:

F = 2 × C = 2 × 160 = 320°F

∴ The temperature on the Fahrenheit scale that is twice the temperature on the Celsius scale is 320°F.
Hence, the correct option is 3) 320°F.

\(\implies C_v = \dfrac{R}{0.4} = \dfrac{5}{2}R\)

From \(C_p = R +C_v\)

We get \(C_p = R+\dfrac{5}{2} R = \dfrac{7}{2}R\)

\(\therefore \gamma = \dfrac{C_p}{C_v} = \dfrac{7/2}{5/2} = 1.4\)

Thus the gas must be made up of rigid diatomic molecules.

Concept:

In this case, the final temperature after equilibrium is reached can be determined by considering the temperature changes of the gases and applying the principle of conservation of energy. The partition remains rigid, so no mechanical work is done, and energy transfers solely by heat between the two gases until they reach thermal equilibrium.

Calculation:

The heat lost by the hot gas is equal to the heat gained by the cold gas. Using the formula:

Q = m × c × ΔT

Where:

• Q is the heat transferred
• m is the mass of the gas
• c is the specific heat capacity of the gas
• ΔT is the temperature change

Given the specific heats, masses, and the initial temperatures of the two gases, the final temperature can be calculated. The temperature after equilibrium would be a weighted average considering the different masses and specific heats of the two gases.

We know,

Q = mC_pΔt for a constant pressure process

Q = mC_vΔt for a constant volume process

Thus,

Q_upper = 2 × (7/2) × (T - 400)

Q_lower = 2 × (3/2) × (700 - T)

But,

Heat given by the lower compartment = Heat gained by the upper compartment

Therefore, 2 × (7/2) × (T - 400) = 2 × (3/2) × (700 - T)

Therefore, T = 490 K

CONCEPT:

There are 4 laws to thermodynamics:

Zeroth law of thermodynamics: 

• If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

First law of thermodynamics: 

• Energy can neither be created nor destroyed. It can only change forms. In any process, the total energy of the universe remains the same.
• For a thermodynamic cycle, the net heat supplied to the system is equals the net work done by the system.

ΔQ = ΔU + ΔW

where ΔQ = change in heat, ΔU = change in internal energy and ΔW = change in work done

Second Law of Thermodynamics:

1. Clausius statement: It is impossible for a self-acting machine to transfer heat from a colder body to a hotter one without the aid of an external agency
2. Kelvin-Planck’s statement: It is impossible to design an engine that extracts heat and fully utilizes it into work without producing any other effect.

Third law of thermodynamics: 

• As the temperature approaches absolute zero, the entropy of a system approaches a constant minimum.
• ΔST = 0K = 0

Where ΔS = change in entropy 

EXPLANATION:

• The First Law of Thermodynamics tells us about the concept of internal energy. Therefore option 1 is incorrect.
• The Second Law of Thermodynamics tells us that some form of energy gets lost whenever energy is transferred or transformed. Therefore option 2 is incorrect.
• From above it is clear that the Zeroth Law of Thermodynamics defines the concept of temperature. Therefore option 3 is correct.
• The Third Law of Thermodynamics tells us about the concept of entropy. Therefore option 4 is incorrect.

Concept: 

• Temperature: It is the measure of the degree of hotness and coldness of a body.
  • The SI unit of temperature is Kelvin (K).

Fahrenheit and Celsius are measurements of temperature and are related to each other as follows:

C = (F - 32) × \(\frac{5}{9}\) 

Where C is the temperature in Celsius and F is the temperature in Fahrenheit.

Explanation:

Since we need temperature in fahrenheit and celsius to be equal:

Now, let C = F = x

So,

x = (x - 32) × \(\frac{5}{9}\)

or, 9x = 5x – 160

or, 4x = -160

or, x = -40

Therefore, °C = °F = -40°

Additional Information

Kelvin is the SI unit of temperature. K = C + 273 

The correct answer is Humidity.

Key Points  

• The rate of evaporation decreases with an increase in Humidity.
• The rate of evaporation mainly depends on these factors:
  • Temperature: The rate of evaporation increases with an increase in temperature.
  • Surface area: The rate of evaporation increases with an increase in surface area.
  • Humidity: The amount of water vapour present in the air is called humidity.
  • The rate of evaporation decreases with an increase in humidity.
  • Wind speed: Evaporation increases with an increase in wind speed.

Additional Information

• Ambient Temperature:
  • ​Ambient temperature is the air temperature of any object or environment where equipment is stored. 
• Evaporation:
  • It is the process of changing of a liquid into water vapour below its boiling point.

The correct answer is Dew point temperature.

Key Points

• Dew point temperature (DPT):
  • It is a temperature at which moisture present in the atmosphere starts condensing or it is the temperature at which the first droplet of moisture is formed.
  • As we know that for each pressure, the air has a specific saturation temperature, therefore for fully saturated air DBT, WBT and DPT are equal.
  • When the relative humidity of the air is 100%, i.e the air is saturated, the dew point temperature (DPT) equals the wet-bulb temperature (WBT), which is also equal to the dry-bulb temperature.
  • So DBT = WBT = DPT

Additional Information

• Relative humidity:
  • It is defined as the ratio of the mass of vapour to the mass of vapour under saturation conditions.
  • Relative humidity represents vapour absorption capacity.

CONCEPT:

Celsius scale:

• In this scale, a lower fixed point (ice point) is designated as 0° and the upper fixed point (steam point) is designated as 100°.
• The temperature measured on this scale was all in degrees Celsius (° C).

Fahrenheit scale:

• On this scale of the temperature scale, the melting point of ice is considered to be 32° F and the boiling point of water is 212° F.
• The change in temperature of 1° F corresponds to a change of less than 1° C on the Celsius scale.

Kelvin scale:

• We also know the Kelvin temperature scale as the thermodynamic scale. 
• On the Kelvin scale, the boiling point of water is considered to be 373.15 K and its freezing point is 273.15 K.
• It is assumed that at 0 K there is no relative motion of particles,
• The change in temperature of 1° K corresponds to a change of less than 1° C on the Celsius scale.
• Whereas all these units of temperatures are related to each other by the following relationship:

\(⇒ \frac{{F - 32}}{9} = \frac{C}{5} = \frac{{K - 273.15}}{5}\)

CALCULATION:

Given  - T = 10⁰C

• Since the number of divisions in both scales, that is in Kelvin scale and degree Celsius scale is 100, so there will be an equal change in both scales.
• And each degree change in the Centigrade scale equals a similar change in the Kelvin scale of measurement.
• Thus, the corresponding rise in temperature of the gas on the Kelvin scale is 10 K. Hence, option 3 is the answer

Concept:

Thermometer: ​

• A device that measures the temperature is called a thermometer.
• A thermometer is based on the principle of thermal expansion. 
• Mercury, liquid metal with high density is used. 
• More the heat more will be the expansion.  

Kink

• The kink is a constriction that prevents the movement of mercury in the tube.
• Due to this, the mercury takes time to reach a given temperature reading and also does not fall rapidly.

​

Conclusion:

• The Kink do not allows the mercury level to fall down just after we take it out from mouth. 
• We have to give jerk to the thermometer so that we can bring it down and use it again. 
• No such kink is present in laboratory thermometer. 
• So, the correct option is clinical thermometer. 

• We should clean clinical thermometer with antiseptic after use.

CONCEPT:

• Temperature: It is the measure of the degree of hotness and coldness of a body.
  • The SI unit of temperature is Kelvin (K).
  • The major temperature scales are:
    • Celsius scale: It is also known as the centigrade scale and the most commonly used scale. It is defined from assigning 0° C to 100° C of freezing and boiling point of water at 1 atmospheric pressure.
    • Kelvin scale: It is the base unit of temperature, denoted with K.
      • There are no negative numbers on the Kelvin scale as the lowest is 0 K.

The relation between Celsius and Kelvin is given by:

° C + 273.15 = K

EXPLANATION:

Given that:

The ice point of water = 0 °C

Temperature (T) =  0 °C

°C + 273.15 = K

⇒ K = 273.15 Kelvin

So option 1 is correct.

The correct option is 3.

CONCEPT:

• Heat: The form of energy that transfers due to temperature difference is called heat.
  • When a body is given the heat, the molecular vibration of the body increases and the body tries to expand its size.
  • Thus the volume of the body increases by heating.
• Density: The mass per unit volume is called density.
  • If the body is heated the volume increases so its density decreases.

EXPLANATION:

• When the glass heated, it expands and the density decreases.
• When it is suddenly cooled, its density tries to decrease in some part of the glass and in some part it remains as it is.
• Due to this density difference, the glass breaks. So option 3 is correct.

Additional Information

• The thermal conductivity and electrical conductivity of glass are very less. 

CONCEPT:

Celsius scale:

• In this scale, the lower fixed point (ice point) is taken at 0° and the upper fixed point  (steam point) is taken at 100°.
• The temperature measured on this scale is all in degrees Celsius (°C).

Fahrenheit scale:

• This scale of temperature has a lower fixed point (ice point) of 32° F and an upper fixed point  (steam point) of 212° F.
• The change in temperature of 1° F corresponds to a change of less than 1° on the Celsius scale.

Kelvin scale:

• The Kelvin temperature scale is also known as the thermodynamic scale. The triple point of water is also selected to be the zero of the scale of temperature.
• The temperatures measured on this scale are in Kelvin (K).

All these temperatures are related to each other by the following relationship –

\(\frac{{F - 32^\circ }}{9} = \frac{C}{5} = \frac{{K - 273}}{5}\)
EXPLANATION: 
Given – the temperature of a place 113 on the Fahrenheit scale.
The relation between Fahrenheit and Kelvin is

\(\frac{{F - 32^\circ }}{9} = \frac{{K - 273}}{5}\)

\(\therefore \frac{{113 - 32^\circ }}{9} = \frac{{K - 273}}{5}\)

\(9 = \frac{{K - 273}}{5}\)

CONCEPT:

• Temperature: A physical quantity that measures the degree of hotness or coolness of the body is known as Temperature.
  • Temperature is measured in Celsius (°C), Fahrenheit (°F), and Kelvin.
• Absolute temperature Scale: The Kelvin scale is an absolute temperature scale. When the temperature is measured in Kelvin.
  • This means that the theoretically lowest possible temperature is assigned the value of zero.
• Absolute Zero: Zero degrees on the Kelvin scale is known as absolute zero i.e. 0 K.
• It is theoretically the point at which there is no molecular motion to produce thermal energy.

EXPLANATION:

• Absolute zero temperature is 0 Kelvin temperature.
• Practically there is no temperature possible less than absolute zero or 0 K.
• So the correct answer is option 1.