WorksheetsChemistry Quiz on Compounds and Elements
Total questions: 30
Worksheet time: 15mins
A student says: "Oxygen gas is a compound because it has two atoms in each molecule (O₂)." Which is correct?
The student is correct
Oxygen gas is a compound because it has atoms bonded together
Oxygen gas is an element because both atoms are the same type
Oxygen gas is not a substance
Which of the following is NOT an example of a compound?
Table salt
Carbon dioxide
Hydrogen gas
Water
A certain liquid is made up of two elements chemically combined in a fixed ratio. On heating, it breaks down into two different gases. This liquid is most likely:
Water
Mercury
Alcohol
Oil
A pure sample of a substance always contains identical molecules. Which of these could it be?
Sugar
Milk
Sea water
Brass
Which of these statements is true about molecules?
Molecules can be broken down into atoms by chemical changes or means
Molecules are always visible with a microscope
Molecules always contain atoms of different elements
Molecules are the smallest particles of matter
Two elements, X and Y, form a compound XY₂. Which of these is true?
The ratio of atoms is fixed at 1:2
The ratio can change depending on conditions
XY₂ is a mixture of X and Y
XY₂ contains 2 molecules of X and 1 of Y
Which is most likely to be an alloy (mixture of metals)?
Bronze
Sodium chloride
Graphite
Methane
Which situation shows a chemical change forming a compound?
Mixing sugar in water
Melting ice
Burning magnesium in air to form magnesium oxide
Breaking glass
A gas cylinder contains oxygen. If all the gas is released, which of these remains in the cylinder?
Atoms of oxygen
Molecules of oxygen
Nothing (vacuum)
Oxygen atoms and molecules
The symbol for the element iron is Fe. Why is it Fe and not Ir or In?
It is based on its Latin name
It is randomly chosen
Fe means “ferrite” in English
Fe stands for “Ferrous metal”
A mixture of iron filings and sulfur powder is heated strongly. A black solid forms which cannot be separated by a magnet. What happened?
The mixture melted
A physical change occurred
A compound (iron sulfide) was formed
The sulfur evaporated
Why is air considered a mixture and not a compound?
Its components cannot be separated
Its components are chemically combined
Its components can be separated physically and are not in fixed proportions
Air has no elements
Which of these has exactly the same composition everywhere?
Tap water
Pure carbon dioxide
Sea water
Milk
When a chemical symbol has two letters, the second letter is always:
Capital
Small
A number
Optional
In a water molecule, hydrogen and oxygen are held together by:
Physical force
Magnetic force
Chemical bonds
Gravitational force
Which of the following is the correct way to write the symbol for calcium?
ca
Ca
CA
cA
The chemical symbol for sodium is “Na” because:
It stands for “Natural”
It comes from the Latin name “Natrium”
It was the first element discovered
It means “Not acidic”
Which of the following pairs is incorrectly matched?
Fe – Iron
Ag – Silver
Pb – Lead
K – Krypton
The molecular formula of carbon dioxide is CO₂. This means:
One molecule has 2 carbon atoms and 1 oxygen atom
One molecule has 1 carbon atom and 2 oxygen atoms
The gas contains carbon and oxygen in any ratio
One molecule has 2 oxygen molecules combined
Which of these is the correct chemical formula for water?
H₂O
HO₂
H₂O₂
OH₂
The number written below and to the right of a chemical symbol in a formula is called:
Subscript
Superscript
Coefficient
Index number
Which of these formulas represents a molecule made up of four atoms?
CO₂
CH₄
H₂O
None
Which is true about the formula NaCl?
It shows sodium and chlorine are physically mixed
It shows sodium and chlorine chemically combined in a fixed ratio
It shows one molecule of sodium joined with two molecules of chlorine
It shows sodium and chlorine can be separated easily
If the formula of a compound is Al₂O₃, how many oxygen atoms are present in 2 molecules of it?
3
6
9
12
Which of the following is a diatomic molecule of an element?
CO₂
H₂O
O₂
NaCl
A compound has the formula C₆H₁₂O₆. Which of the following is true?
It contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms per molecule
It contains 6 molecules of CH₂O
It is always a solid
It is a mixture of carbon, hydrogen, and oxygen
Which statement about the formula H₂SO₄ is correct?
It has 2 sulfur atoms
It has 4 hydrogen atoms
It has 2 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms
It is called hydrogen sulfate
Which of these symbols represents an element that is a metal?
O
S
Mg
Cl
The formula of methane is CH₄. Which conclusion is wrong?
Each molecule has one carbon atom
Each molecule has four hydrogen atoms
It is a compound of carbon and hydrogen
It has 4 carbon atoms for each hydrogen atom
The chemical formula for calcium carbonate is CaCO₃. What does this tell us?
It contains 1 atom each of calcium, carbon, and oxygen
It contains 1 calcium atom, 1 carbon atom, and 3 oxygen atoms per molecule
It is a mixture of calcium, carbon, and oxygen
It contains calcium oxide and carbon dioxide together
