Q 01/05

Which chemist created the first widely accepted periodic table?

A) Antoine Lavoisier

B) Marie Curie

C) Dmitri Mendeleev

D) John Dalton

Answer · why

C) Dmitri Mendeleev

Dmitri Mendeleev left gaps in his table for elements nobody had found and forecast their properties; three of them were discovered within twenty years...

Q 02/05

Beyond solid, liquid and gas, what is usually counted as the fourth state of matter, the stuff of stars and lightning?

A) Colloid

B) Liquid crystal

C) Superfluid

D) Plasma

Answer · why

D) Plasma

Plasma forms when a gas is heated or electrified until electrons break free of its atoms, which is why it conducts electricity and glows, as in a neon...

Q 03/05

What type of chemical reaction absorbs heat energy from its surroundings?

A) Redox

B) Catalytic

C) Exothermic

D) Endothermic

Answer · why

D) Endothermic

Endothermic changes soak up heat from their surroundings, which is how an instant cold pack works: squeezing it lets ammonium nitrate dissolve in wate...

Q 04/05

Dry ice is the frozen form of which gas?

A) Nitrogen

B) Carbon monoxide

C) Carbon dioxide

D) Nitrous oxide

Answer · why

C) Carbon dioxide

Carbon dioxide has no liquid state at normal pressure, so dry ice at −78.5 °C turns straight into gas, keeping food frozen without leaving a puddle.

Q 05/05

What subatomic particle found in the nucleus of an atom carries a positive electric charge?

A) Electron

B) Proton

C) Neutron

D) Photon

Answer · why

B) Proton

Proton: the number of protons fixes which element an atom is, so no chemical reaction could turn lead into gold as the alchemists hoped; that takes a ...