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NCEA L1 ChemBio study materials
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NCEA L1 ChemBio practice questions

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Question 1Chemistry

Which particle in an atom carries a negative charge?

  1. Electron Correct answer.
  2. Neutron
  3. Nucleus
  4. Proton

Explanation

Electrons are the negatively charged particles that occupy the shells around the nucleus. Protons are positive and neutrons are neutral, and the nucleus is a region containing both.

Question 2Chemistry

What is the chemical symbol for the element potassium?

  1. Po
  2. K Correct answer.
  3. P
  4. Pt

Explanation

Potassium's symbol K comes from its Latin name kalium. P is phosphorus, Po is polonium and Pt is platinum.

Question 3Chemistry

A substance has a fixed volume but takes the shape of its container. In which state is it?

  1. Gas
  2. Solid
  3. Plasma
  4. Liquid Correct answer.

Explanation

Liquids have particles close together with a fixed volume but they can flow to fill the shape of the container. Solids keep both shape and volume, and gases fill both the shape and volume of the container.

Question 4Chemistry

In a neutral atom, the number of protons is always equal to the number of what?

  1. Electrons Correct answer.
  2. Energy levels
  3. Neutrons
  4. Nucleons

Explanation

A neutral atom has no overall charge, so the positive protons must be balanced by an equal number of negative electrons. The neutron number can vary between isotopes.

Question 5Chemistry

Which change of state describes a solid turning directly into a gas?

  1. Sublimation Correct answer.
  2. Melting
  3. Condensation
  4. Evaporation

Explanation

Sublimation is the direct change from solid to gas without passing through the liquid state. Melting is solid to liquid and evaporation is liquid to gas.

Question 6Chemistry

Which of these is a compound rather than an element or a mixture?

  1. Sea water
  2. Air
  3. Oxygen gas
  4. Sodium chloride Correct answer.

Explanation

A compound contains two or more elements chemically combined in fixed proportions, as in sodium chloride. Oxygen is an element, while air and sea water are mixtures.

Question 7Chemistry

What does the atomic number of an element tell you?

  1. The number of electron shells
  2. The number of protons in the nucleus Correct answer.
  3. The total number of protons and neutrons
  4. The number of neutrons in the nucleus

Explanation

The atomic number counts the protons in the nucleus and so identifies the element. The total of protons plus neutrons is the mass number.

Question 8Chemistry

Which observation shows that a chemical reaction has taken place when iron nails are left in damp air?

  1. The nails keep the same mass and appearance
  2. The nails become colder
  3. A reddish-brown coating forms Correct answer.
  4. The nails become shinier

Explanation

Rusting produces a new reddish-brown substance, iron oxide, which is a sign of a chemical change. A physical change would not create a new substance with a different colour and texture.

Question 9Chemistry

An atom of chlorine has 17 protons and 18 neutrons. What is its mass number?

  1. 35 Correct answer.
  2. 18
  3. 17
  4. 36

Explanation

The mass number is the sum of protons and neutrons, so 17 + 18 = 35. The proton count alone is the atomic number.

Question 10Chemistry

Which statement best explains why a gas can be compressed easily but a liquid cannot?

  1. The spaces between gas particles are much larger Correct answer.
  2. Gas particles are chemically bonded to each other
  3. Gas particles have more mass than liquid particles
  4. Gas particles are larger than liquid particles

Explanation

In a gas the particles are far apart with large empty spaces between them, so they can be pushed closer together. In a liquid the particles are already close together and resist further compression.

Question 11Chemistry

Magnesium burns in oxygen to form magnesium oxide. Which word equation is correct?

  1. magnesium oxide + oxygen → magnesium
  2. magnesium oxide → magnesium + oxygen
  3. magnesium + oxygen → magnesium oxide Correct answer.
  4. magnesium + magnesium oxide → oxygen

Explanation

In a combustion reaction the reactants are written on the left and the product on the right. Magnesium combines with oxygen to produce magnesium oxide.

Question 12Chemistry

Sodium has the electron arrangement 2,8,1. What is the most likely charge on a sodium ion?

  1. 1−
  2. 1+ Correct answer.
  3. 3+
  4. 2+

Explanation

Sodium loses its single outer electron to gain the stable arrangement 2,8. Losing one negative electron leaves a single positive charge.

Question 13Chemistry

Which of these is a physical change rather than a chemical change?

  1. Wood burning
  2. Iron rusting
  3. Ice melting Correct answer.
  4. Milk souring

Explanation

Melting ice changes only the state of water, and the substance can be frozen back, so it is a physical change. Rusting, burning and souring all create new substances.

Question 14Chemistry

Two isotopes of carbon are carbon-12 and carbon-14. How do their atoms differ?

  1. They have different numbers of electrons
  2. They have different numbers of neutrons Correct answer.
  3. They have different numbers of protons
  4. They have different chemical symbols

Explanation

Isotopes of an element have the same proton number but different neutron numbers. Carbon-12 has six neutrons and carbon-14 has eight.

Question 15Chemistry

A compound contains 40% calcium, 12% carbon and 48% oxygen by mass. Which is its simplest empirical formula? (Ar: Ca = 40, C = 12, O = 16)

  1. CaC₂O₃
  2. CaCO₃ Correct answer.
  3. Ca₂CO₃
  4. CaCO₂

Explanation

Divide each percentage by its atomic mass: 40/40 = 1, 12/12 = 1, 48/16 = 3. The ratio is 1:1:3, giving CaCO₃.

Question 16Chemistry

Which statement correctly describes what happens to particles when a liquid evaporates?

  1. Particles break apart into atoms
  2. The particles slow down and lock into place
  3. The fastest particles escape from the surface Correct answer.
  4. New particles are formed chemically

Explanation

Evaporation occurs when the most energetic particles at the surface gain enough energy to escape into the gas state. The remaining liquid cools as a result.

Question 17Chemistry

Which observation would confirm that a clear liquid is pure water rather than a salt solution?

  1. It conducts electricity well
  2. It boils at exactly 100 °C at standard pressure Correct answer.
  3. It is colourless and transparent
  4. It freezes into a white solid

Explanation

A pure substance has a sharp, fixed boiling point. Dissolved salt raises the boiling point and spreads it over a range.

Question 18Chemistry

In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water form when 4 moles of hydrogen react completely with excess oxygen?

  1. 1 mole
  2. 4 moles Correct answer.
  3. 2 moles
  4. 8 moles

Explanation

The equation shows 2 moles of hydrogen produce 2 moles of water, a 1:1 ratio. So 4 moles of hydrogen produce 4 moles of water.

Question 19Chemistry

Which list contains only ions?

  1. Na, Cl₂, Mg
  2. Na⁺, Cl⁻, Mg²⁺ Correct answer.
  3. H₂O, CO₂, NaCl
  4. Na⁺, Cl₂, Mg²⁺

Explanation

Each species in this list carries a charge, marking it as an ion. Neutral atoms or molecules carry no charge symbol.

Question 20Chemistry

A student heats a hydrate and the mass falls from 25.0 g to 16.0 g. If all the lost mass is water, what is the percentage of water in the hydrate?

  1. 9%
  2. 64%
  3. 36% Correct answer.
  4. 56%

Explanation

The water lost is 25.0 − 16.0 = 9.0 g. Dividing 9.0 by the original 25.0 g and multiplying by 100 gives 36%.

Question 21Chemistry

Which statement best explains why the noble gases are very unreactive?

  1. They have no neutrons in their nuclei
  2. They have very large atoms
  3. They exist only as liquids
  4. They have full outer electron shells Correct answer.

Explanation

A full outer shell is a stable arrangement, so noble gases have little tendency to gain, lose or share electrons. This makes them chemically inert.

Question 22Chemistry

An unknown ion X²⁻ has the electron arrangement 2,8,8. What is the atomic number of the neutral element X?

  1. 14
  2. 16 Correct answer.
  3. 18
  4. 20

Explanation

The ion has 18 electrons in total. Because X²⁻ has gained two electrons, the neutral atom has 18 − 2 = 16 electrons, so its atomic number is 16.

Question 23Chemistry

A sample of an element contains 75% of an isotope with mass number 35 and 25% of an isotope with mass number 37. What is its relative atomic mass?

  1. 35.0
  2. 36.5
  3. 36.0
  4. 35.5 Correct answer.

Explanation

Calculate the weighted average: (0.75 × 35) + (0.25 × 37) = 26.25 + 9.25 = 35.5. The average lies closer to 35 because that isotope is more abundant.

Question 24Chemistry

Which change would shift the position of equilibrium in a gaseous reaction toward the products?

  1. Adding more of the product
  2. Lowering the temperature of any reaction
  3. Increasing the total pressure of any reaction
  4. Removing a product as it forms Correct answer.

Explanation

According to Le Chatelier's principle, removing a product lowers its concentration and the system shifts to replace it, favouring the forward reaction. Pressure and temperature effects depend on the specific reaction.

Question 25Chemistry

Two colourless solutions are mixed and a white precipitate forms. Which conclusion is best supported?

  1. A physical change of state has taken place
  2. The mixture has simply been diluted
  3. A chemical reaction has occurred forming an insoluble product Correct answer.
  4. The solutions were both pure water

Explanation

A precipitate is a new insoluble solid formed when ions in solution combine, which indicates a chemical reaction. Dilution or a change of state would not create a solid from two clear solutions.

Question 26Chemistry

Which particle is found in the nucleus of an atom and has no electrical charge?

  1. Neutron Correct answer.
  2. Ion
  3. Electron
  4. Proton

Explanation

The nucleus contains protons and neutrons; protons are positively charged and neutrons have no charge. Electrons are negatively charged and orbit the nucleus.

Question 27Chemistry

Which of these is a homogeneous mixture?

  1. Oil and water
  2. Salt water Correct answer.
  3. Granite
  4. Concrete

Explanation

A homogeneous mixture has the same composition throughout. Salt water is a solution where the salt is evenly dissolved in the water.

Question 28Chemistry

Which group in the periodic table contains the alkali metals?

  1. Group 18
  2. Group 1 Correct answer.
  3. Group 2
  4. Group 17

Explanation

Alkali metals are the elements in Group 1 (excluding hydrogen), such as lithium, sodium and potassium. They are soft, reactive metals with one valence electron.

Question 29Chemistry

Which statement describes a covalent bond?

  1. A bond formed by the attraction between metal cations and delocalised electrons.
  2. A bond formed by the attraction between oppositely charged ions.
  3. A bond formed by the sharing of electrons between atoms. Correct answer.
  4. A bond formed by the transfer of electrons from one atom to another.

Explanation

Covalent bonding occurs when non-metal atoms share pairs of electrons to achieve stable electron arrangements. Ionic bonds involve electron transfer, and metallic bonds involve delocalised electrons.

Question 30Chemistry

Which of the following is a balanced chemical equation?

  1. 2H₂ + O₂ → 2H₂O Correct answer.
  2. H₂ + O₂ → H₂O
  3. H₂ + O₂ → H₂O₂
  4. 2H₂ + 2O₂ → 2H₂O

Explanation

A balanced equation has the same number of each type of atom on both sides. In 2H₂ + O₂ → 2H₂O there are 4 hydrogen atoms and 2 oxygen atoms on each side.

Question 31Chemistry

Which of these is an example of a combustion reaction?

  1. Zn + 2HCl → ZnCl₂ + H₂
  2. CaCO₃ → CaO + CO₂
  3. AgNO₃ + NaCl → AgCl + NaNO₃
  4. CH₄ + 2O₂ → CO₂ + 2H₂O Correct answer.

Explanation

Combustion is the reaction of a substance with oxygen to produce oxides, often releasing energy. The reaction of methane with oxygen produces carbon dioxide and water.

Question 32Chemistry

Which particle is responsible for carrying a positive charge in an electric current through a metal wire?

  1. Proton
  2. Neutron
  3. Electron Correct answer.
  4. Ion

Explanation

In metals, electrical conductivity occurs due to the movement of delocalised electrons. These electrons are negatively charged, but conventional current is described in the opposite direction.

Question 33Chemistry

Which of these is a property of ionic compounds?

  1. They do not dissolve in water.
  2. They conduct electricity when molten or dissolved in water. Correct answer.
  3. They have low melting points.
  4. They are usually gases at room temperature.

Explanation

Ionic compounds consist of a lattice of ions. When molten or dissolved, the ions are free to move and carry an electric current.

Question 34Chemistry

What is the pH of a neutral solution at 25°C?

  1. 7 Correct answer.
  2. 1
  3. 0
  4. 14

Explanation

At 25°C, a neutral solution has equal concentrations of hydrogen and hydroxide ions, giving a pH of 7. Acids have pH less than 7, and bases have pH greater than 7.

Question 35Chemistry

Which of the following is the correct electron arrangement for a chlorine atom (atomic number 17)?

  1. 2,8,6
  2. 2,8,7 Correct answer.
  3. 2,8,8
  4. 2,8,5

Explanation

Chlorine has 17 electrons. These fill the shells in order: 2 in the first shell, 8 in the second, and 7 in the third.

Question 36Chemistry

Which statement best explains why the melting point of magnesium oxide (MgO) is much higher than that of sodium chloride (NaCl)?

  1. MgO has ions with higher charges, leading to stronger electrostatic attractions. Correct answer.
  2. MgO has a covalent network structure, while NaCl is ionic.
  3. MgO has weaker ionic bonds because magnesium is a smaller ion.
  4. MgO has a lower lattice energy due to its smaller ions.

Explanation

Both compounds are ionic, but Mg²⁺ and O²⁻ ions have higher charges than Na⁺ and Cl⁻ ions. The electrostatic force between ions increases with charge, so more energy is needed to break the lattice in MgO.

Question 37Chemistry

Which of the following is the correct formula for aluminium oxide?

  1. AlO
  2. Al₂O
  3. Al₂O₃ Correct answer.
  4. Al₃O₂

Explanation

Aluminium forms Al³⁺ ions and oxygen forms O²⁻ ions. To balance the charges, two Al³⁺ ions (total +6) and three O²⁻ ions (total -6) are needed, giving Al₂O₃.

Question 38Chemistry

Which statement correctly describes the shape of a methane (CH₄) molecule?

  1. Trigonal planar, with bond angles of about 120°.
  2. Tetrahedral, with bond angles of about 109.5°. Correct answer.
  3. Linear, with bond angles of 180°.
  4. Bent, with bond angles of about 104.5°.

Explanation

In methane, the central carbon atom is bonded to four hydrogen atoms with no lone pairs. The electron pairs repel equally, giving a tetrahedral shape with bond angles of approximately 109.5°.

Question 39Chemistry

Which of the following is the correct IUPAC name for CH₃CH₂CH₂OH?

  1. Propanoic acid
  2. Propan-2-ol
  3. Propan-1-ol Correct answer.
  4. Propanal

Explanation

The longest carbon chain has three carbon atoms (propane). The hydroxyl group (-OH) is on the first carbon, so the name is propan-1-ol.

Question 40Chemistry

Which of these is an addition reaction?

  1. Ethene reacting with bromine to form 1,2-dibromoethane Correct answer.
  2. Propene being hydrated to propan-2-ol
  3. Ethane reacting with chlorine in the presence of UV light
  4. Ethanol being oxidised to ethanoic acid

Explanation

An addition reaction involves two molecules combining to form a single product without the loss of any atoms. Ethene and bromine add together to form 1,2-dibromoethane.

Question 41Chemistry

Which statement best explains why the rate of a chemical reaction increases when the temperature is raised?

  1. A greater proportion of particles have energy greater than the activation energy. Correct answer.
  2. The particles become larger and collide more often.
  3. The activation energy of the reaction decreases.
  4. The concentration of the reactants increases.

Explanation

Raising the temperature increases the average kinetic energy of particles, so more particles have enough energy to overcome the activation energy barrier. This leads to more successful collisions per unit time.

Question 42Chemistry

Which of these is the correct half-equation for the reduction of chlorine gas to chloride ions?

  1. 2Cl⁻ → Cl₂ + 2e⁻
  2. Cl₂ + e⁻ → 2Cl⁻
  3. Cl₂ → 2Cl⁻ + 2e⁻
  4. Cl₂ + 2e⁻ → 2Cl⁻ Correct answer.

Explanation

Reduction is the gain of electrons. Chlorine (Cl₂) gains two electrons to form two chloride ions (Cl⁻), giving the half-equation Cl₂ + 2e⁻ → 2Cl⁻.

Question 43Chemistry

What is the mass of 0.50 mol of carbon dioxide (CO₂)? (Ar: C = 12, O = 16)

  1. 44 g
  2. 11 g
  3. 88 g
  4. 22 g Correct answer.

Explanation

The molar mass of CO₂ is 12 + 2×16 = 44 g/mol. Therefore, 0.50 mol has a mass of 0.50 × 44 = 22 g.

Question 44Chemistry

Which of the following is the correct electron configuration for a calcium ion, Ca²⁺? (Atomic number of Ca = 20)

  1. 2,8,8,2
  2. 2,8,9
  3. 2,8,8 Correct answer.
  4. 2,8,7

Explanation

A neutral calcium atom has 20 electrons with the configuration 2,8,8,2. The Ca²⁺ ion has lost two electrons from its outermost shell, giving 2,8,8.

Question 45Chemistry

Which statement about the periodic table is correct?

  1. The number of electron shells increases across a period from left to right.
  2. Atomic radius generally increases across a period from left to right.
  3. Atomic radius generally decreases across a period from left to right. Correct answer.
  4. Metallic character increases across a period from left to right.

Explanation

Across a period, the number of protons increases while electrons are added to the same shell. The increased nuclear charge pulls the electrons closer, so atomic radius decreases.

Question 46Chemistry

Which of the following is the strongest intermolecular force present in liquid water?

  1. Dipole-dipole attraction
  2. Ionic bonding
  3. Hydrogen bonding Correct answer.
  4. London dispersion forces

Explanation

Water molecules form hydrogen bonds because hydrogen is bonded to a highly electronegative oxygen atom. These are stronger than ordinary dipole-dipole attractions and dispersion forces.

Question 47Chemistry

Which of these statements about a catalyst is correct?

  1. It changes the equilibrium position of a reversible reaction.
  2. It increases the rate of reaction by providing an alternative pathway with lower activation energy. Correct answer.
  3. It is consumed in the reaction and must be replenished.
  4. It increases the rate of reaction by increasing the activation energy.

Explanation

A catalyst speeds up a reaction by lowering the activation energy, often by providing a different reaction mechanism. It is not consumed overall and does not affect the position of equilibrium.

Question 48Chemistry

Which of the following is the correct balanced equation for the complete combustion of ethane (C₂H₆)?

  1. 2C₂H₆ + 5O₂ → 4CO₂ + 6H₂O
  2. C₂H₆ + 3O₂ → 2CO₂ + 3H₂O
  3. 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O Correct answer.
  4. C₂H₆ + 2O₂ → 2CO + 3H₂O

Explanation

Complete combustion of a hydrocarbon produces carbon dioxide and water. For ethane, the balanced equation is 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O, which has 4 C, 12 H and 14 O on each side.

Question 49Chemistry

A student adds zinc granules to excess dilute hydrochloric acid. Which change would increase the initial rate of reaction without changing the amount of zinc?

  1. Using zinc powder instead of granules Correct answer.
  2. Using a larger volume of more dilute acid
  3. Cooling the reaction mixture
  4. Adding water to the acid

Explanation

Increasing the surface area of a solid reactant increases the frequency of collisions with acid particles, raising the reaction rate. Zinc powder has a much larger surface area than granules.

Question 50Chemistry

In the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), which change would increase the equilibrium yield of ammonia?

  1. Adding a catalyst
  2. Increasing the pressure Correct answer.
  3. Increasing the temperature
  4. Decreasing the concentration of nitrogen

Explanation

According to Le Chatelier's principle, increasing pressure shifts the equilibrium towards the side with fewer gas molecules. There are 4 moles of gas on the left and 2 on the right, so higher pressure favours ammonia formation.