Conservation of mass | Starter Quiz | Oak National Academy

What are the building blocks of all matter?

• molecules

• compounds

• atoms

Answer explanation

Atoms are the building blocks of all matter.

Atoms cannot be created or ...

Answer explanation

Atoms cannot be created or destroyed. The number at the start of a reaction in the reactants is the same as at the end in the products.

Name the elements and number of atoms of each type in (NH₄)₂SO₄

• nitrogen (1) hydrogen (4) sodium (4)

• nitrogen hydride (2) sulfur oxide (4)

• nitrogen (2), hydrogen (8), sulfur (1) and oxygen (4)

• nitrogen (2), hydrogen (8) and oxygen (4)

• ammonium (2), sulfur (1) and oxygen (4)

Answer explanation

(NH₄)₂SO₄ is ammonium sulfate and contains the following elements and atoms of each; nitrogen (2), hydrogen (8), sulfur (1) and oxygen (4).

Hydrogen reacts with oxygen to form water as steam. Match up the following statements to make complete sentences about this reaction.

• There are the same number of atoms ...

• gases shown by the state symbol (g).

• The word equation for the reaction is:

• of oxygen (2) and hydrogen (4) in the reactants and products.

• Water is ...

• hydrogen + oxygen → water (dihydrogenoxide)

• All the reactants and products are ...

• 2H₂ (g) + O₂(g) → 2H₂O(g)

• The symbol equation for the reaction is:

• a gas as it is steam.

Answer explanation

Hydrogen and oxygen react to form water as steam = all gases. The number of atoms in the reactants and products must be the same as matter cannot be created or destroyed. 2H₂ = 4 atoms + O₂ = 2 atoms → 2H₂O (4 atoms of hydrogen and 2 of oxygen).

Methane (CH₄) burns to produce carbon dioxide (CO₂) and water (H₂O). Count how many atoms of each element are on the left and right hand side of the equation. Are they equal? CH₄ + 2O₂ → CO₂ + 2H₂O

• carbon (1), hydrogen (4) oxygen (4)-> carbon (1), hydrogen (4) oxygen (4) No

• carbon (1), hydrogen (4) oxygen (2)-> carbon (1), hydrogen (4) oxygen (3) Yes

• carbon (4), hydrogen (4) oxygen (2)-> carbon (2), hydrogen (4) oxygen (3) Yes

• carbon (1), hydrogen (4) oxygen (4)-> carbon (1), hydrogen (4) oxygen (4) Yes

Answer explanation

carbon (1), hydrogen (4) oxygen (4)-> carbon (1), hydrogen (4) oxygen (4) Yes the equation is balanced as there are equal numbers of each element in the starting substances (reactants) and those formed (products).