Chemical reaction

What are the substances called that start a chemical reaction?

• Elements

• Reactants

• Compounds

• Products

What is the chemical symbol for oxygen?

• H

• O

• N

• C

In the chemical formula H2O, what does the '2' represent?

• Two molecules of water

• Two atoms of oxygen

• Two atoms of hydrogen

• Two elements combined

What does the arrow in a chemical equation signify?

• The reactants in a reaction

• The products formed in a reaction

• The end of a reaction

• The start of a reaction

What remains unchanged in terms of quantity during a chemical reaction?

• The number of molecules

• The number of atoms

• The number of compounds

• The number of elements