Heat Temperature Thermodynamics Competitive Exams
100 questions · General Science
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Question 1 of 100
The change of a solid directly into a gas without becoming liquid is called
ExplanationCamphor and naphthalene balls sublime.
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Question 2 of 100
Gaps are left between railway tracks to allow for
ExplanationOtherwise the rails would buckle in hot weather.
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Question 3 of 100
Latent heat is the heat
ExplanationIt is used to break or form bonds between particles.
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Question 4 of 100
In an isochoric (constant volume) process, the work done by the gas is
ExplanationW = PΔV and ΔV = 0.
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Question 5 of 100
When ice melts, it changes from
ExplanationThe temperature remains 0 °C during melting.
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Question 6 of 100
The dew point is the temperature at which
ExplanationCooling below it causes condensation as dew.
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Question 7 of 100
The specific heat capacity of a substance is the heat required to raise the temperature of
ExplanationIts SI unit is J/(kg·K).
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Question 8 of 100
Mercury is used in thermometers because it
ExplanationIt also does not wet the glass.
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Question 9 of 100
The efficiency of a Carnot engine can never be 100% because
Explanationη = 1 − Tc/Th = 1 only if Tc = 0 K.
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Question 10 of 100
The ratio γ = Cₚ/Cᵥ for a monatomic ideal gas is
ExplanationCₚ = 5R/2 and Cᵥ = 3R/2.
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Question 11 of 100
Boiling occurs
ExplanationEvaporation occurs at any temperature but only at the surface.
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Question 12 of 100
The area enclosed by a closed loop (cycle) on a P–V diagram represents
ExplanationOver a complete cycle ΔU = 0, so the net work equals the net heat absorbed.
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Question 13 of 100
The first law of thermodynamics states that
ExplanationHeat added is used for internal energy increase and work done.
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Question 14 of 100
The second law of thermodynamics states that heat cannot flow spontaneously from
ExplanationIt gives a direction to natural processes.
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Question 15 of 100
A heat engine
ExplanationExamples are petrol engines and steam engines.
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Question 16 of 100
The total entropy of the universe in any spontaneous process
ExplanationThis is one statement of the second law.
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Question 17 of 100
In an isothermal process for an ideal gas, the change in internal energy is
ExplanationInternal energy depends only on temperature.
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Question 18 of 100
In a bimetallic strip heated uniformly, the strip bends so that the metal with the higher coefficient of expansion is
ExplanationIt expands more and lengthens on the outside of the curve.
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Question 19 of 100
A metal spoon in hot tea becomes hot due to
ExplanationHeat passes along the spoon.
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Question 20 of 100
Which of the following is the main source of heat on Earth?
ExplanationIt provides almost all the energy reaching the Earth.
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Question 21 of 100
The latent heat of fusion of ice is about
ExplanationAbout 336 kJ is needed to melt 1 kg of ice at 0 °C.
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Question 22 of 100
A thermometer is used to measure
ExplanationIt measures how hot or cold a body is.
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Question 23 of 100
A perfect black body is a
ExplanationIt absorbs all radiation that falls on it.
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Question 24 of 100
A refrigerator removes 400 J of heat from the cold space using 100 J of work. Its coefficient of performance is
ExplanationCOP = Qc/W = 400/100.
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Question 25 of 100
The sea breeze in coastal areas blows from the
ExplanationLand heats faster than water, causing convection currents.
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Question 26 of 100
Mayer's relation for an ideal gas is
ExplanationMore heat is needed at constant pressure because the gas does work.
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Question 27 of 100
Water is unusual because it has its maximum density at
ExplanationThis anomalous expansion allows fish to survive under frozen lakes.
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Question 28 of 100
Boyle's law states that at constant temperature the pressure of a fixed mass of gas is
ExplanationPV = constant.
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Question 29 of 100
Heat is a form of
ExplanationIt flows from a hotter body to a colder body.
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Question 30 of 100
The zeroth law of thermodynamics is the basis for the concept of
ExplanationIf A and B are each in thermal equilibrium with C, they are in equilibrium with each other.
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Question 31 of 100
The normal temperature of the human body is about
ExplanationIt is equal to 98.6 °F.
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Question 32 of 100
The thermometer used to measure human body temperature is the
ExplanationIt has a range of about 35 °C to 42 °C.
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Question 33 of 100
A temperature of 100 °C in Fahrenheit is
Explanation°F = (9/5 × °C) + 32 = 212 °F.
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Question 34 of 100
The heat required to raise the temperature of 2 kg of water by 10 °C (c = 4,200 J/kg·K) is
ExplanationQ = mcΔT = 2 × 4200 × 10.
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Question 35 of 100
For a monatomic ideal gas, the molar specific heat at constant volume (Cᵥ) is
ExplanationIt has three translational degrees of freedom.
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Question 36 of 100
Which of the following is NOT a method of heat transfer?
ExplanationSublimation is a change of state.
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Question 37 of 100
A gas at 2 atm and 4 L expands isothermally to 8 L. The new pressure is
ExplanationP₁V₁ = P₂V₂ → P₂ = 2 × 4/8.
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Question 38 of 100
In an adiabatic process,
ExplanationThe first law gives ΔU = −W.
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Question 39 of 100
The heat required to melt 2 kg of ice at 0 °C (L = 3.36 × 10⁵ J/kg) is
ExplanationQ = mL = 2 × 3.36 × 10⁵.
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Question 40 of 100
Metals are good conductors of heat because they have
ExplanationFree electrons carry energy quickly.
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Question 41 of 100
According to the pressure law, at constant volume the pressure of a gas is proportional to its
ExplanationP/T = constant.
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Question 42 of 100
A refrigerator works by
ExplanationA compressor does work on the refrigerant.
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Question 43 of 100
The root mean square speed of gas molecules is proportional to
Explanationv_rms = √(3RT/M).
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Question 44 of 100
A gas expands at constant pressure of 1 × 10⁵ Pa by 0.02 m³. The work done is
ExplanationW = PΔV = 10⁵ × 0.02 = 2,000 J.
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Question 45 of 100
A thermos flask keeps liquids hot for long because it
ExplanationIt has a vacuum between double walls and silvered surfaces.
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Question 46 of 100
The SI unit of temperature is
ExplanationThe Celsius scale is also widely used, with 0 °C = 273.15 K.
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Question 47 of 100
The heat needed to convert 1 kg of ice at 0 °C to water at 20 °C (L = 3.36 × 10⁵ J/kg; c = 4,200 J/kg·K) is
ExplanationQ = 3.36 × 10⁵ + 1 × 4200 × 20 = 4.2 × 10⁵ J.
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Question 48 of 100
On the Fahrenheit scale, water boils at
ExplanationIt freezes at 32 °F.
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Question 49 of 100
The change of a gas into a liquid is called
ExplanationWater vapour condenses on a cold glass.
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Question 50 of 100
Convection currents are used in
ExplanationHot water rises while cooler water sinks.
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Question 51 of 100
The temperature at which Celsius and Fahrenheit readings are equal is
ExplanationC = F at −40 °.
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Question 52 of 100
Absolute zero is
ExplanationIt is the lowest possible temperature.
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Question 53 of 100
Solids generally
ExplanationParticles vibrate more and take more space.
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Question 54 of 100
The triple point of water is at about
ExplanationIce, liquid water and vapour coexist in equilibrium.
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Question 55 of 100
Heat always flows from
ExplanationIt continues until the temperatures become equal.
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Question 56 of 100
While a substance changes its state, its temperature
ExplanationThe supplied heat is used to change the state.
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Question 57 of 100
6 L of gas at 300 K is heated at constant pressure to 450 K. The new volume is
ExplanationV₂ = V₁ × T₂/T₁ = 6 × 450/300 = 9 L.
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Question 58 of 100
Charles's law states that at constant pressure the volume of a gas is directly proportional to its
ExplanationV/T = constant, with T in kelvin.
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Question 59 of 100
A gas absorbs 500 J of heat and does 200 J of work. The change in internal energy is
ExplanationΔU = Q − W = 500 − 200.
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Question 60 of 100
Water boils at ______ at normal atmospheric pressure.
ExplanationIt is 212 °F on the Fahrenheit scale.
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Question 61 of 100
Pure water freezes at
ExplanationIt is 32 °F or 273.15 K.
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Question 62 of 100
Temperature is a measure of
ExplanationHeat is the energy transferred due to temperature difference.
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Question 63 of 100
If the absolute temperature of a gas is made four times, the rms speed of its molecules becomes
Explanationv_rms ∝ √T.
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Question 64 of 100
The change in length of a rod on heating is given by
Explanationα is the coefficient of linear expansion.
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Question 65 of 100
Water has a high specific heat capacity, so it
ExplanationThis is why it is used as a coolant.
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Question 66 of 100
The inner walls of a vacuum flask are silvered to reduce heat loss by
ExplanationShiny surfaces reflect radiation and emit poorly.
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Question 67 of 100
Which of the following is a good conductor of heat?
ExplanationMetals have free electrons.
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Question 68 of 100
Joule's mechanical equivalent of heat is approximately
ExplanationIt shows that work and heat are equivalent forms of energy.
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Question 69 of 100
Transfer of heat through solids without movement of the material is called
ExplanationHeat passes from particle to particle.
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Question 70 of 100
A gas is compressed rapidly and its temperature rises because
ExplanationThe process is nearly adiabatic.
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Question 71 of 100
The ideal gas equation is
ExplanationR = 8.314 J/(mol·K).
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Question 72 of 100
200 g of water at 80 °C is mixed with 300 g of water at 20 °C. The final temperature is
ExplanationT = (200 × 80 + 300 × 20)/500 = 22,000/500 = 44 °C.
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Question 73 of 100
According to Newton's law of cooling, the rate of loss of heat of a body is proportional to
ExplanationIt holds approximately for small temperature differences.
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Question 74 of 100
Evaporation of a liquid causes
ExplanationThe fastest molecules escape, lowering the average energy of the rest.
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Question 75 of 100
A cup of hot tea cools down on standing because heat is lost to
ExplanationHeat flows from the hot tea to the cooler surroundings.
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Question 76 of 100
A Carnot engine operates between 600 K and 300 K. Its efficiency is
Explanationη = 1 − Tc/Th = 1 − 300/600 = 0.5.
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Question 77 of 100
Transfer of heat in liquids and gases by movement of the fluid is called
ExplanationHot fluid rises and cold fluid sinks.
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Question 78 of 100
Woollen clothes keep us warm because they
ExplanationWool and air are insulators.
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Question 79 of 100
Heat from the Sun reaches the Earth by
ExplanationRadiation needs no medium and can travel through a vacuum.
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Question 80 of 100
The Kelvin–Planck statement of the second law says that
ExplanationSome heat must be rejected to a cold reservoir.
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Question 81 of 100
Real gases deviate most from ideal gas behaviour at
ExplanationIntermolecular forces and molecular size become important.
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Question 82 of 100
The entropy change when 600 J of heat is absorbed reversibly at 300 K is
ExplanationΔS = Q/T = 600/300.
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Question 83 of 100
A temperature of 27 °C in kelvin is
ExplanationK = °C + 273 = 300 K.
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Question 84 of 100
Steam at 100 °C causes a more severe burn than boiling water at 100 °C because steam
ExplanationThe latent heat of vaporisation is released on the skin.
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Question 85 of 100
The third law of thermodynamics states that
ExplanationIt is not possible to reach absolute zero in a finite number of steps.
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Question 86 of 100
A bimetallic strip is used in
ExplanationTwo metals with different expansion rates bend when heated.
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Question 87 of 100
Land heats faster than the sea in the daytime because land has
ExplanationWater takes more heat to raise its temperature.
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Question 88 of 100
According to the kinetic theory, gas pressure is caused by
ExplanationMore frequent and harder collisions mean higher pressure.
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Question 89 of 100
The principle of calorimetry states that
ExplanationIt follows from conservation of energy.
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Question 90 of 100
Entropy is a measure of the
ExplanationEntropy of an isolated system never decreases.
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Question 91 of 100
The latent heat of vaporisation of water is about
ExplanationThe latent heat of fusion of ice is about 3.36 × 10⁵ J/kg.
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Question 92 of 100
The SI unit of heat is
ExplanationCalorie is another unit: 1 cal ≈ 4.2 J.
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Question 93 of 100
The rate of heat conduction through a slab is given by
Explanationk is the thermal conductivity.
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Question 94 of 100
Wien's displacement law states that the wavelength of maximum emission of a black body
ExplanationλₘₐₓT = constant, so hotter bodies emit at shorter wavelengths.
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Question 95 of 100
A rod of length 2 m and α = 12 × 10⁻⁶ per °C is heated by 50 °C. Its increase in length is
ExplanationΔL = αLΔT = 12 × 10⁻⁶ × 2 × 50 = 1.2 × 10⁻³ m.
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Question 96 of 100
Which of the following is a poor conductor (insulator) of heat?
ExplanationWood and plastic are used for handles of cooking utensils.
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Question 97 of 100
In a pressure cooker, food cooks faster because
ExplanationWater boils at above 100 °C inside it.
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Question 98 of 100
Dark-coloured surfaces
ExplanationThat is why white clothes are preferred in summer.
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Question 99 of 100
The average translational kinetic energy of a gas molecule is
ExplanationIt is proportional to the absolute temperature.
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Question 100 of 100
According to the Stefan–Boltzmann law, the power radiated by a black body is proportional to
ExplanationDoubling the absolute temperature increases the power 16 times.
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