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
Correct answer
Explanation
The correct answer is B, 4 degrees Celsius. 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.
Option A is the freezing point, where water turns to ice; ice is in fact less dense than water, which is why it floats. Option C is the boiling point at normal atmospheric pressure, where water is at its most expanded as a liquid. Option D lies below the freezing point, where pure water at ordinary pressure is solid. The property matters in nature because in a pond in winter the water at four degrees sinks, the colder water floats and freezes at the top, and fish survive in the liquid water below.
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
Show answer
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 →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
Show answer
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
Show answer
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 →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
Show answer
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.
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
Show answer
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.
Read the full explanation →