2F - 6. Molecules and Compounds

What is a compound?

• A pure substance formed from two or more elements

• A mixture of elements

• A gas at room temperature

• A single element

What is the chemical formula for water?

• HO

• O2H

• H2O

• H2O2

What is oxidation?

• The process of removing oxygen

• The process of adding oxygen

• The formation of a compound

• The breaking down of a substance

What is a reducing agent?

• A substance that is always a gas

• A substance that does not react

• A substance that reduces another substance

• A substance that oxidises another substance

What does the Law of constant composition state?

• Elements cannot combine

• Compounds have a fixed composition

• Mixtures have a fixed composition

• Compounds can vary in composition

Which of the following is a mixture?

• Hydrogen

• Air

• Carbon dioxide

• Water

What happens when iron filings and sulfur are heated?

• They become a gas

• They release oxygen

• They form a mixture

• They undergo a chemical reaction

What is an exothermic reaction?

• A reaction that occurs in water

• A reaction that produces gas

• A reaction that releases heat

• A reaction that absorbs heat

What is the proton number of an element?

• The total number of particles in the atom

• The number of electrons in the atom

• The number of neutrons in the nucleus

• The number of protons in the nucleus

What is the mass number of an atom?

• The total number of protons and neutrons

• The total number of electrons

• The number of neutrons only

• The number of protons only