The first law of thermodynamics is essentially a statement of
- A.The conservation of energy
- B.The increase of entropy
- C.Thermal equilibrium
- D.The unattainability of absolute zero
Correct answer
Explanation
The correct answer is A, the conservation of energy. The first law says that the heat supplied to a system is equal to the increase in its internal energy plus the external work it does. Nothing is lost and nothing is created; energy only changes its form, which is the principle of conservation applied to heat.
Option B belongs to the second law, which introduces entropy and says that it never decreases in an isolated system. Option C belongs to the zeroth law, which says that two bodies each in thermal equilibrium with a third are in equilibrium with one another and which makes the measurement of temperature possible. Option D belongs to the third law, which says that the entropy of a perfect crystal tends to zero as the temperature tends to absolute zero and that absolute zero cannot be reached.
Read the full article: Heat and Thermodynamics: Laws, Latent Heat and Transfer
Practice Questions
View allThe SI unit of heat is the
- A.Calorie
- B.Joule
- C.Kelvin
- D.Watt
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Heat is a form of energy in transit, so it is measured in the same unit as work and energy, the joule, which is one newton metre.
Read the full explanation →Water has its maximum density at a temperature of
- A.0 degrees Celsius
- B.4 degrees Celsius
- C.100 degrees Celsius
- D.Minus 4 degrees Celsius
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Water behaves abnormally between zero and four degrees: it contracts as it is heated in that range and expands again above four degrees, so the same mass occupies its least volume, and therefore has its greatest density, at four degrees Celsius.
Read the full explanation →The latent heat of vaporisation of water is about
- A.80 calories per gram
- B.540 calories per gram
- C.336 calories per gram
- D.2260 calories per gram
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This is the heat that one gram of water at a hundred degrees Celsius must absorb to become steam at the same temperature, with no rise in temperature at all; the same quantity is released when steam condenses back to water.
Read the full explanation →In a vacuum flask, the vacuum between the two walls prevents heat transfer mainly by
- A.Conduction and convection
- B.Radiation only
- C.Conduction only
- D.Neither conduction nor convection
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Both of these modes need matter: conduction passes energy from particle to particle and convection carries it by the movement of a fluid.
Read the full explanation →Which law of thermodynamics provides the basis for the concept of temperature?
- A.The zeroth law
- B.The first law
- C.The second law
- D.The third law
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It states that if body A is in thermal equilibrium with body C, and body B is also in thermal equilibrium with body C, then A and B are in thermal equilibrium with each other.
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