Section 1: Particles, atoms and bonding

A substance has a fixed volume but takes the shape of the bottom of any container it is poured into. Which state is it in?

Which row describes the particles in a gas?

On a cold morning, drops of water form on the inside of a window. What is the name of this change of state?

A puddle of water dries up on a day when the air temperature is 20 °C. Which statement about this change is correct?

The end of a gas syringe containing air is sealed. The plunger is pushed in slowly so that the temperature of the air stays the same. What happens to the volume and the pressure of the air?

A balloon filled with air is taken from a cold room into a warm room. The pressure of the air around it stays the same. What happens to the balloon?

A sealed steel can of gas is heated. Its volume cannot change. Why does the pressure of the gas increase?

A solid is heated at a steady rate and its temperature is measured. The graph shows the results. Why does the temperature stay at 54 °C between 2 and 6 minutes even though heating continues?

In a heating experiment, the temperature of a substance rises from 20 °C to 54 °C, stays at 54 °C, then rises to 118 °C and stays at 118 °C. What is the state of the substance at 80 °C?

A bottle of perfume is opened in one corner of a still room. A few minutes later the perfume can be smelled on the other side of the room. Which statement explains this?

A crystal of purple potassium manganate(VII) is placed at the bottom of a beaker of water. The purple colour spreads through the water. The experiment is repeated with warmer water. What happens to the colour, and why?

Cotton wool soaked in concentrated ammonia solution is placed at one end of a long glass tube and cotton wool soaked in concentrated hydrochloric acid at the other end. The gases ammonia, NH₃, and hydrogen chloride, HCl, meet and form a white solid. Where does the white solid form, and why? [Mᵣ: NH₃ = 17, HCl = 36.5]

Which gas diffuses fastest at room temperature? [Aᵣ: H = 1, C = 12, N = 14, O = 16, Cl = 35.5]

Which substance is a compound?

Iron filings and powdered sulfur are mixed. Part of the mixture is then heated strongly, and it glows and forms a black solid. Which statement is correct?

A sample of gas contains some molecules made of two joined oxygen atoms and some molecules made of one carbon atom joined to two oxygen atoms. How is the sample best described?

Which statement is true for every compound?

Which row gives the relative charge and the relative mass of an electron?

What is the proton number (atomic number) of an atom?

An atom of aluminium has proton number 13 and mass number 27. How many protons, neutrons and electrons does it have?

An element has the electronic configuration 2,8,3. In which group and period of the Periodic Table is it?

What is the electronic configuration of a sulfide ion, S²⁻? [Proton number of S = 16]

Why are the noble gases in Group VIII very unreactive?

Carbon-12 and carbon-14 are isotopes of carbon. How are their atoms different?

How many protons, neutrons and electrons are there in the ion ³⁷₁₇Cl⁻?

A sample of neon contains 90.5% neon-20, 0.3% neon-21 and 9.2% neon-22. What is the relative atomic mass of neon in this sample?

Boron has two isotopes, boron-10 and boron-11. The relative atomic mass of boron is 10.8. What is the percentage of boron-10 atoms in boron?

Chlorine-35 and chlorine-37 react in exactly the same way with sodium. Why?

How does a potassium atom form a potassium ion, K⁺?

What is an ionic bond?

Lithium (proton number 3) reacts with fluorine (proton number 9) to form lithium fluoride. Which statement describes what happens to the electrons?

Solid sodium chloride does not conduct electricity, but molten sodium chloride does. Which statement describes this correctly?

Why does solid magnesium oxide not conduct electricity, while molten magnesium oxide does?

Which describes the structure of solid potassium bromide?

Magnesium oxide melts at 2852 °C and sodium chloride at 801 °C. Which explanation fits these data best?

Calcium (proton number 20) reacts with chlorine (proton number 17) to form calcium chloride. What are the electronic configurations of the ions formed?

What happens when a covalent bond forms between two atoms?

In a dot-and-cross diagram of ammonia, NH₃, how many bonding pairs and how many non-bonding (lone) pairs of electrons are around the nitrogen atom?

In a molecule of water, H₂O, how many electrons are in the outer shell of the oxygen atom, and how many of those are in the two bonding pairs?

How many electrons are shared between the two atoms in a nitrogen molecule, N₂?

Which describes the bonding in a molecule of carbon dioxide, CO₂?

How many pairs of electrons are shared in total in one molecule of ethene, C₂H₄?

Methane boils at −162 °C, although the C-H bonds in its molecules are strong. Why is its boiling point so low?

Liquid bromine is made of simple Br₂ molecules. Why is it a poor conductor of electricity?

Why is diamond used on the tips of drills for cutting rock?

Graphite powder is used to lubricate the moving parts of locks. Which feature of its structure makes it a good lubricant?

Graphite is used for electrodes. Why does graphite conduct electricity while diamond does not?

Which describes the structure of silicon(IV) oxide, SiO₂?

Diamond and silicon(IV) oxide have similar physical properties. Which pair of properties do they share, and why?

What is metallic bonding?

Why is copper a good conductor of electricity, both as a solid and when molten?

Gold can be hammered into very thin sheets without breaking. Which explanation is correct?