Q 01/05

Why does water boil cooler on Everest?

A) Colder air

B) Lower pressure

C) Weaker gravity

D) Less oxygen

Answer · why

B) Lower pressure

Lower pressure: the summit air presses down with only about a third of its sea-level force, so water boils at about 70 °C and food takes far longer to...

Q 02/05

Which way does heat never flow on its own?

A) From a hotter body to a colder one

B) From a colder body to a hotter one

C) Between bodies of equal size

D) Through a vacuum

Answer · why

B) From a colder body to a hotter one

From a colder body to a hotter one: heat makes that trip only when work forces it, which is why a refrigerator has to be plugged in.

Q 03/05

Which unit was defined as the heat needed to warm one gram of water by one degree Celsius?

A) The joule

B) The therm

C) The calorie

D) The BTU

Answer · why

C) The calorie

The calorie comes from calor, Latin for heat; confusingly, the 'Calories' on food labels are kilocalories, each enough to warm a whole kilogram of wat...

Q 04/05

What is absolute zero on the Celsius scale?

A) −73.15 °C

B) −273.15 °C

C) −573.15 °C

D) −1,273.15 °C

Answer · why

B) −273.15 °C

−273.15 °C is the bottom of the scale, yet matter would not be perfectly still there: quantum mechanics leaves atoms a residual zero-point motion.

Q 05/05

Which temperature scale is defined with absolute zero as 0?

A) Kelvin

B) Fahrenheit

C) Celsius

D) Réaumur

Answer · why

A) Kelvin

The Rankine scale also starts at absolute zero but uses Fahrenheit-sized degrees.