Q 01/05

Which gas, a molecule of three oxygen atoms, forms a high layer that shields Earth from the Sun's ultraviolet rays?

A) Argon

B) Ozone

C) Radon

D) Xenon

Answer · why

B) Ozone

Ozone takes its name from the Greek word for smell, after the sharp odour it leaves in the air following a lightning strike. The oxygen people breathe...

Q 02/05

Which gas that humans breathe out freezes into dry ice, the solid that makes stage fog without ever melting?

A) Hydrogen sulfide

B) Pure oxygen

C) Water vapour

D) Carbon dioxide

Answer · why

D) Carbon dioxide

Carbon dioxide has no liquid stage at normal air pressure, so dry ice turns straight from a solid into a gas at about −78 °C. The name dry ice began l...

Q 03/05

What does water do as it freezes, unlike most liquids, because its molecules lock into an open six-sided pattern?

A) It expands

B) It shrinks

C) It darkens

D) It sinks

Answer · why

A) It expands

It expands by about 9%, which makes ice less dense than liquid water, so ice floats. That is why ponds freeze from the top down instead of from the bo...

Q 04/05

Which molecule do coffee and tea plants make as a natural pesticide that can paralyse and kill feeding insects?

A) Taurine

B) Theanine

C) Caffeine

D) Nicotine

Answer · why

C) Caffeine

Caffeine is the world's most widely consumed psychoactive drug. In flower nectar a small dose seems to sharpen a honey bee's memory of the reward, so ...

Q 05/05

Which cleaning product, made in Babylon around 2800 BC, has molecules with a water-loving head and a grease-loving tail?

A) Bleach

B) Soap

C) Vinegar

D) Borax

Answer · why

B) Soap

Soap molecules wrap specks of grease in tiny spheres called micelles, tails pointing in and heads pointing out. Plain water can then rinse the trapped...