Year 8 Diagnostic Quiz – Elements, Compounds and Mixtures

Which of the following is a compound?

• Oxygen (O₂)

• Carbon (C)

• Water (H₂O)

• Helium (He)

What is the smallest part of an element?

• Molecule

• Atom

• Compound

• Proton

Which of these is a mixture?

• Salt (NaCl)

• Air

• Oxygen

• Carbon dioxide

Which is a correct symbol for an element?

• Co₂

• H₂O

• C

• NaCl

Elements in the periodic table are arranged by:

• Mass number

• Atomic number

• Alphabetical order

• Number of electrons

Which of the following is a molecule but not a compound?

• O₂

• CO₂

• H₂O

• NaCl

What does a chemical formula represent?

• How many mixtures are in a compound

• The number and types of atoms in a substance

• The melting point of a material

• A type of physical change

Which of the following is a compound?

• Hydrogen (H)

• Helium (He)

• Water (H₂O)

• Gold (Au)

What is a key difference between compounds and mixtures?

• A) Mixtures have fixed ratios

• B) Compounds can be separated physically

• C) Mixtures can be separated physically

• D) Compounds have variable compositions

Which diagram best represents a mixture?

• Identical atoms together

• Atoms joined in fixed ratios

• Different particles not bonded

• A single atom