Q 01/05

Which gemstone, the hardest natural material, is made of the same element as pencil graphite?

A) Ruby

B) Sapphire

C) Diamond

D) Emerald

Answer · why

C) Diamond

Diamond is pure carbon, exactly like graphite, but its atoms lock into a rigid crystal. At room pressure graphite is the stable form, so a diamond is ...

Q 02/05

Which kitchen staple, formula NaCl, joins a soft reactive metal to a poisonous yellow-green gas?

A) Table salt

B) Baking soda

C) Cane sugar

D) White vinegar

Answer · why

A) Table salt

Table salt is sodium chloride. Neither ingredient is safe alone: sodium is a soft, highly reactive metal, and chlorine was used as a poison gas in Wor...

Q 03/05

Which precious metal has the chemical symbol Au, taken from the Latin name aurum?

A) Silver

B) Copper

C) Platinum

D) Gold

Answer · why

D) Gold

Gold is the most malleable metal of all. A single gram can be beaten into a sheet covering one square metre, thin enough to become semi-transparent.

Q 04/05

Which organelle, inherited almost only from the mother, makes the ATP that powers a cell?

A) Ribosome

B) Mitochondrion

C) Golgi apparatus

D) Lysosome

Answer · why

B) Mitochondrion

The mitochondrion keeps its own small genome, similar to a bacterium's. That is a clue to its origin: its ancestor was a free-living microbe that fuse...

Q 05/05

Which phenomenon makes an ambulance siren sound higher as it approaches and lower as it drives away?

A) Doppler effect

B) Coriolis effect

C) Greenhouse effect

D) Photoelectric effect

Answer · why

A) Doppler effect

The Doppler effect is named after Christian Doppler, who described it in 1842. Astronomers use the same shift in starlight to measure how fast stars a...