Q 01/05

Which lizard's grip on glass has long been credited to van der Waals forces from tiny hairs on its feet?

A) Chameleon

B) Iguana

C) Gecko

D) Skink

Answer · why

C) Gecko

Gecko footpads pack about 14,000 hair-like setae into every square millimeter. Forces this weak only add up to a firm grip over a very large contact a...

Q 02/05

Which gemstone is pure carbon, each atom covalently bonded to its neighbors in a rigid 3D network?

A) Diamond

B) Zircon

C) Garnet

D) Amber

Answer · why

A) Diamond

Diamond has more atoms per unit volume than any other known substance, which is why it is both the hardest and the least compressible.

Q 03/05

Which attraction between water molecules makes ice less dense than liquid water, so that it floats?

A) Ionic bonding

B) Hydrogen bonding

C) Covalent bonding

D) Pi stacking

Answer · why

B) Hydrogen bonding

Hydrogen bonding locks the molecules of ice into an open hexagonal framework, so the solid is about 8% less dense than the liquid. Floating ice keeps ...

Q 04/05

Which kitchen staple dissolves in water as whole molecules, not ions, because it is covalently bonded?

A) Table salt

B) Baking soda

C) Cream of tartar

D) Table sugar

Answer · why

D) Table sugar

Table sugar is a non-electrolyte: its molecules stay whole in water instead of breaking into ions. Salt water conducts electricity because its dissolv...

Q 05/05

Which metal, used in light-bulb filaments, owes its record-high melting point to strong bonds between its atoms?

A) Tungsten

B) Titanium

C) Platinum

D) Chromium

Answer · why

A) Tungsten

Tungsten melts at 3,422 °C, hotter than any other metal, and has the highest tensile strength of any pure metal. That toughness puts it in heating ele...