Bonding, structure and properties: GCSE questions with answers

Answer: D Close together in a regular pattern

In a solid, particles are packed in a regular pattern and vibrate in place. In a liquid, they are still close but move around each other. In a gas, they are far apart and move quickly in all directions.

Checked against Pearson Edexcel GCSE Chemistry 1CH0 specification, 2.1 States of matter

Answer: C Condensing

Melting turns a solid into a liquid and freezing turns it back. Boiling turns a liquid into a gas and condensing turns it back. Melting and freezing happen at the melting point; boiling and condensing at the boiling point.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.1 The three states of matter

Answer: C Burning magnesium

In a physical change, such as a change of state or dissolving, no new substance forms and the change is easy to reverse. In a chemical change, such as burning, new substances are made.

Checked against OCR Gateway Chemistry A J248 specification, C1.1b The particle model

Answer: A They vibrate more and move slightly apart

Particles themselves do not grow when heated. They gain energy, vibrate or move faster, and so take up more space. Gas particles have the most energy and solid particles the least.

Checked against OCR Gateway Chemistry A J248 specification, C1.1a The particle model

Answer: A It shows no forces between the particles

The simple model draws particles as solid, inelastic spheres with no forces between them. Real particles attract each other, are not solid spheres, and come in different sizes and shapes. So the model cannot explain why substances melt and boil at different temperatures.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.1 The three states of matter

Answer: A How strong the forces between its particles are

To melt or boil, particles need enough energy to overcome the forces holding them together. The stronger those forces, the more energy is needed and the higher the melting or boiling point.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.1 The three states of matter

Answer: B Weak forces between the molecules

Small molecules such as water and methane have strong covalent bonds inside them but only weak forces between them. Boiling overcomes the weak intermolecular forces, not the covalent bonds, so little energy is needed.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.3 and 4.2.2.4 Properties of ionic compounds and small molecules

Answer: B A simple molecular substance

Ionic compounds, giant covalent substances and most metals have strong bonds all through the structure, so they melt at high temperatures. Simple molecular substances only need weak intermolecular forces overcome, so they melt and boil at low temperatures.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.3 and 4.2.2.4 Properties of ionic compounds and small molecules

Answer: A Melts at −7 °C, boils at 59 °C

Compare the temperature with the melting and boiling points. Below the melting point it is a solid; between the melting and boiling points it is a liquid; above the boiling point it is a gas.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.1 The three states of matter

Answer: B Melts at 115 °C, boils at 445 °C

A substance is solid below its melting point, liquid between its melting and boiling points, and a gas above its boiling point. A substance that boils at 78 °C is a gas at 90 °C but a liquid at 20 °C.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.1 The three states of matter

Answer: D Ionic

There are three types of strong chemical bond. Ionic bonding happens between metals and non-metals, covalent bonding between non-metal atoms, and metallic bonding in metals and alloys.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.1 Chemical bonds

Answer: A A giant lattice of oppositely charged ions

An ionic compound is a giant structure of ions arranged in a regular lattice. Strong electrostatic forces act in all directions between the oppositely charged ions. A sodium ion and a chloride ion are not a molecule.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.3 Ionic compounds

Answer: D Carbon dioxide, CO₂

Compounds of non-metals such as CO₂, H₂O, CH₄ and NH₃ are small molecules. Diamond and silicon dioxide are giant covalent structures. Metal and non-metal compounds such as NaCl and MgO are ionic. Note that CO₂ and SiO₂ look alike but have very different structures.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.4 Covalent bonding

Answer: A A very large molecule of repeating units

Polymers such as poly(ethene) are very large molecules made of many repeating units joined into long chains. The atoms in each chain are held by strong covalent bonds.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.4 Covalent bonding

Answer: A Positive ions in a sea of delocalised electrons

Metals are giant structures with atoms arranged in a regular pattern of layers. Their outer electrons are delocalised, free to move through the whole structure, which holds the positive metal ions together.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.5 Metallic bonding

Answer: A Attraction between oppositely charged ions

An ionic bond is the strong electrostatic attraction between oppositely charged ions. A covalent bond is a pair of electrons shared between two atoms, held by attraction to both nuclei.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.1 Chemical bonds

Answer: B Sodium transfers an electron to chlorine

When a metal reacts with a non-metal, the metal atom loses its outer electrons and the non-metal atom gains them. Both ions end up with a full outer shell, like a noble gas.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.2 Ionic bonding

Answer: C An atom or group of atoms with a charge

An ion is an atom, or a group of atoms, that has a positive or negative charge because electrons have been lost or gained. Na⁺ is an ion; Ne, H₂O and CH₄ have no charge.

Checked against Pearson Edexcel GCSE Chemistry 1CH0 specification, 1.22 Key concepts in chemistry

Answer: D It loses two electrons

Group 1 and 2 metals lose 1 or 2 electrons, making 1+ and 2+ ions. Group 6 and 7 non-metals gain 2 or 1 electrons, making 2− and 1− ions. Either way the ion gets a full outer shell.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.2 Ionic bonding

Answer: D Attraction between positive ions and delocalised electrons

In a metal the outer electrons are delocalised. There is a strong electrostatic attraction between these free electrons and the positive metal ions, which is metallic bonding.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.5 Metallic bonding

Answer: D 4

Each covalent bond is one shared pair of electrons. In a dot and cross diagram, methane has four shared pairs, ammonia three and water two. Each hydrogen shares one pair.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.4 Covalent bonding

Answer: B Two

Each oxygen atom has six outer electrons and needs two more, so the two atoms share two pairs: a double bond. Hydrogen and chlorine each need one more electron, so they share one pair.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.4 Covalent bonding

Answer: C Eight outer electrons, one from sodium, and a 1− charge

Dots and crosses show which atom each electron came from. Sodium gives its one outer electron to chlorine, so the chloride ion has a full shell of eight, one of them from sodium, and a 1− charge. Magnesium gives two electrons to oxygen, making Mg²⁺ and O²⁻.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.2 Ionic bonding

Answer: A The 3D shape of the molecule

A dot and cross diagram is good for showing where electrons come from and which are shared. But it is flat, so it does not show the real 3D shape of a molecule or the relative sizes of the atoms.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.4 Covalent bonding

Answer: D Bonds are forces, not solid sticks

Every model leaves something out. Ball and stick models show bonds as sticks with gaps, but bonds are forces and the atoms are much closer. Diagrams of giant structures show only a tiny part of the real lattice.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.1.3 Ionic compounds

Answer: B Its ions are free to move

Ionic compounds conduct electricity when melted or dissolved in water, because the ions are free to move and carry charge. In the solid the ions are fixed in the lattice, so it does not conduct.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.3 and 4.2.2.4 Properties of ionic compounds and small molecules

Answer: C Their molecules have no overall charge

Molecules have no overall charge, so substances made of them do not conduct. The bigger the molecules, the stronger the intermolecular forces between them, so the higher the melting and boiling points.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.3 and 4.2.2.4 Properties of ionic compounds and small molecules

Answer: D Delocalised electrons move through the metal

Metals conduct electricity and heat because their delocalised electrons move through the structure and carry charge and energy. The atoms are in layers that can slide over each other, so metals can be bent and shaped.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.5 to 4.2.2.8 Polymers, giant covalent structures, metals and alloys

Answer: C Different-sized atoms distort the layers so they cannot slide easily

Pure metals are fairly soft because their layers of atoms slide easily. In an alloy, atoms of different sizes distort the layers, so they cannot slide over each other as easily and the alloy is harder.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.5 to 4.2.2.8 Polymers, giant covalent structures, metals and alloys

Answer: D The intermolecular forces between the long chains are fairly strong

Polymer molecules are very long. The forces between these large molecules are relatively strong compared with those between small molecules, so polymers are solids at room temperature.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.5 to 4.2.2.8 Polymers, giant covalent structures, metals and alloys

Answer: A It does not have these bulk properties

Bulk properties such as shine, hardness, melting point and conducting electricity come from how huge numbers of atoms are bonded and arranged. A single atom on its own does not have them.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.2.1 The three states of matter

Answer: D 4

Carbon is in Group 4, so it has four outer electrons. It shares each of them with another atom, forming four covalent bonds and a full outer shell of eight.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.3.1 and 4.2.3.2 Diamond and graphite

Answer: C Carbon atoms join into chains and rings

Carbon atoms can bond strongly to each other, forming chains of almost any length, branches and rings. They can also form families of similar compounds. That is why there is a vast range of natural and synthetic carbon compounds.

Checked against AQA GCSE Chemistry 8462 specification, 4.7.1.2 Fractional distillation and petrochemicals

Answer: A Each carbon atom is bonded to four others by strong covalent bonds

In diamond, every carbon atom forms four strong covalent bonds in a giant structure. That makes it very hard with a very high melting point, so it is used in cutting tools. All its outer electrons are in bonds, so it does not conduct.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.3.1 and 4.2.3.2 Diamond and graphite

Answer: D Its layers can slide over each other

In graphite, each carbon atom bonds to three others, making layers of hexagonal rings with no covalent bonds between the layers. The layers slide easily, so graphite is a lubricant. One electron from each atom is delocalised, so it conducts and is used for electrodes.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.3.1 and 4.2.3.2 Diamond and graphite

Answer: D Many strong covalent bonds in the layers must break

Graphite is soft because its layers slide, but melting it means breaking the many strong covalent bonds within the layers. That takes a lot of energy, so graphite, like diamond, has a very high melting point.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.3.1 and 4.2.3.2 Diamond and graphite

Answer: C A single layer of graphite

Graphene is one layer of graphite, just one atom thick. Its strong covalent bonds make it very strong, and its delocalised electrons let it conduct electricity, so it is useful in electronics and composites.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.3.3 Graphene and fullerenes

Answer: B Molecules of carbon atoms with hollow shapes

Fullerenes are molecules of carbon atoms with hollow shapes, such as balls and tubes. They are based on hexagonal rings, sometimes with rings of five or seven atoms. The first found was buckminsterfullerene, C₆₀, which is shaped like a ball.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.3.3 Graphene and fullerenes

Answer: D 1 to 100 nm

Nanoparticles are 1 to 100 nm across, while an atom is about 0.1 nm. So a nanoparticle contains a few hundred atoms. It is much bigger than an atom but far smaller than anything you can see.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.4.1 Sizes of particles and their properties

Answer: C 1 × 10⁻⁹ m

One nanometre is a billionth of a metre, 1 × 10⁻⁹ m. A typical atom has a radius of about 1 × 10⁻¹⁰ m, so ten atoms side by side span only a few nanometres.

Checked against AQA GCSE Chemistry 8462 specification, 4.2.4.1 Sizes of particles and their properties