Topic 2 Bonding, Structure And The Properties Of Matter

Question 1

Element X forms ions with a 2- charge. What is the group number of element X?

Answer 1

6. Elements in group 6 gain two electrons to get a stable electronic structure, forming 2- ions.

Question 2

If an atom loses two electrons to form an ion. What charge will the ion have?

Answer 2

2+ as electrons are negatively charged.

Question 3

Describe how an ionic bond forms between a metal atom and a non-metal atom. Explain your answer in terms of electron transfer.

Answer 3

The metal atom loses electrons to form a positively charged ion. The non-metal atom gains these electrons to form a negatively charged ion. These oppositely charged ions are strongly attracted to each other by electrostatic forces forming an ionic bond.

Question 4

5. A dot and cross diagram of sodium flouride is shown on the right. Only the outer shells are shown in the diagram. Sodium is in group 1 and flourine is in group 7. Identify two errors in the diagram.

Answer 4

The charge on the sodium ion should be 1+. Sodium is in group 1 of the periodic table so it loses one electron to get a full outer shell forming 1+ ions. The flouride ion should have eight electrons in it’s outer shell (only seven are shown in the diagram) as elements in group 7 gain 1 electron to gain a full outer shell of 8 electrons

Question 5

Do ionic compounds have high or low boiling points?

Answer 5

Ionic compounds have high melting points. This is due to the strong electrostatic forces of attraction that exist between the ions.

Question 6

Give one limitation of using ball and stick modes to represent ionic compounds?

Answer 6

• the relative sizes of the ions may not be shown
• there aren’t any gaps between the ions where the model suggests there are

Question 7

Explain why ionic compounds conduct electricity when molten but not when solid.

Answer 7

In order for a substance to conduct electricity, it must contain charged partcles that are free to move around and carry the current. The ions in a solid ionic compound are held together in a rigid lattice structure, so can’t move arund. When an ionic compound melts the ionic bonds break and the ions become free to move and carry an electric current.

Question 8

Describe the structure and bonding in an ionic compound.

Answer 8

Ionic componds have a giant ionic lattice structure. The ions form a closely packed, regular lattice held together by ionic bonds. There are strong electrostatic forces of attraction between oppositely charged ions in all directions.

Question 9

5. An ionic compound is made up of calcium and chloride ions. Calcium is in group 2 and chlorine is in group 7. What is the empirical formula of compound A?

Answer 9

Calcium is in group 2 so it loses two electrons to get a full outer shell and form a 2+ ion.
Chloine is in group 7 so it gains an electron get a full outer shell and form a 1- ion.
The compound has to be neutral overall, so you need chlorine ions to cancel out the 2+ charge of the calcium ion.
So the empirical formula of the compound is CaCl₂

Question 10

How many electrons does each atom donate to a single covalent bond?

Answer 10

The atoms in a single covalent bond donate 1 electron each.

Question 11

T or F? Non-metals can form covalent bonds with each other.

Answer 11

True - covalent bonds only form between non-metal atoms

Question 12

Describe some limitations of using a displayed formula to represent a molecule?

Answer 12

• doesn’t show you the 3d structure of the molecule.
• doesn’t give you any information about which atoms the electrons in the covalent bonds have come from.

Question 13

6. Explain why carbon forms four covalent bonds with hydrogen atoms in CH₄.

Answer 13

A non-metal atom will generally try to form enough covalent bonds to fill its outer shell. Carbon has four electrons in its outer shell, so needs to form 4 single covalent bonds in order to have 8 electrons in its outer shell.

Question 14

7. Why dosen’t a compound with the formula NH₅ exist?

Answer 14

Nitrogen already has 5 electrons in its outer shell so it only needs to form 3 single covalent bonds to get a full outer shell. If nitrogen frmed 5 covalent bonds with hydrogen atoms, it would have more than 8 electrons in its outer shell.

Question 15

1. What is the name of the molecule shoen in the dot and cross diagram below?

Answer 15

Hydrogen chloride

Question 16

2. Which of the following molecules contains a triple bond?

H₂O
NH₃
N₂
Cl₂

Answer 16

N₂ - it contains an N≡N triple bond

An atom of nitrogen has 5 electrons in its outer shell, so it needs 3 electrons to get a full outer shell.

It can do this by forming a triple covalent bond with another nitrogen atom.

Question 17

Why don’t simple molecular substances conduct electricity?

Answer 17

Simple molecular substances aren’t charged so there aren’t any free electrons or ions to carry an electric current.

Question 18

A says ‘’ The covalent bonds between nitrogen atoms are stronger than the covalent bonds between hydrogen atoms so the boiling point of nitrogen will be higher than that of hydrogen. Explain why A isn’t necessarily correct.

Answer 18

The covalent bonds within a molecule aren’t broken whe a substance boils. It’s the weak intermolecular forces that exist between the molecules that get broken. The strength of the intermolecular forces dosen’t depend on the strength of the covalent bonds within the molecule, so even though nitrogen has stronger covalent bonds than hydrogen, it might not have a higher boiling point.

Question 19

How are the atoms in a polymer joined together.

Answer 19

The atoms in a polymer are joined together by covalent bonds.

Question 20

Which element makes up diamond?

Answer 20

Carbon

Question 21

Look at the compound below. What physical state will it be in at room temperature?

Answer 21

It will be solid. The compound is a polymer and the intermolecular forces between polymer molecules are relatively strong. This means they require a fair amount of energy to break, so almost all polymers are solids at room temperature.

Question 22

Why do giant covalent structures have high melting points?

Answer 22

In order to melt a giant covalent structure, you need to break the strong covalent bonds that exist between the atoms. This requires a lot of energy so giant covalent structures have high melting points.

Question 23

5. The melting points of two substances are shown in the table below. Explain the difference between the melting points of the two substances, in terms of structure and bonding.

Answer 23

In order to melt silica, you have to break the strong covalent bonds that exist between the atoms. This requires a lot of energy so silica has a high melting point. Polyethene melts when relatively weak intermolecular forces are broken. Intermolecular forces are much weaker than covalent bonds, so polyethene has a much lower melting point than silica.

Question 24

T or F? A buckminsterfullerine molecule is shaped like a ball.

Answer 24

True. It’s a hollow sphere made up of carbon atoms arranged in rings.

Question 25

In graphene how many covalent bonds does each carbon atom form?

Answer 25

3 - carbon atoms in graphene are arranged in hexagons.

Question 26

Why can carbon nanotubes conduct electricity?

Answer 26

In a carbon nanotube, each carbon only forms three bonds, so each carbon atom has a delocalised electron that’s free to move around. These electrons carry thermal energy around the structure (so carbon nanotubes are good conductors of heat).

Question 27

Describe the structure of graphite.

Answer 27

Graphite is made up of carbon atoms arranged hexagons. These hexagons join together to form sheets, which are held together weakly (by intermolecular forces).

Question 28

Give one appliation of graphene. Explain why the properties of graphene make it suitable for that application.

Answer 28

• strong but light so it can be added to composites to inprove strength without adding much weight.
• can conduct electricity through the whole stucture, so can be used in electronics.

Question 29

Why do most metals have high melting points?

Answer 29

they’re held together by stong metallic bonds, which require a lot of energy to break. it’s these bonds that get broken when metals melt, so most metals have high melting points.

Question 30

Why can most metals be easily bent and shaped?

Answer 30

The atoms in a metal are arranged in layers which acn slide over each other, so metals can be bent or shaped without breaking the structure of the metal.

Question 31

Copper is a metal that is often used in electrical wiring. Explain why the structure of copper allows it to conduct electricity.

Answer 31

Copper has a giant metallic structure made up of metal ions and delocalised free electrons. The delocalised free electrons can move around the structure and carry charge.

Question 32

Bronze is an alloy made up of copper and small amounts of tin. descibe how the structure of bronze makes it harder than pure copper.

Answer 32

Bronze contains atoms of two different sizes (copper and tin). The tin atoms distort the layers of the copper atoms, which makes it harder for the layers to slide over each other, so bronze is harder than pure copper.

Question 33

J is shopping for a new garden bench. All the metal benches he sits on feel colder than any of the wooden benches he tries, even though they’re all the same temperature. Suggest why.

Answer 33

Metals are good conductors of heat (they contain delocalised free electrons). So when j sits on the metal benches the heat is being moved away from his body much quicker than when he sits on the wooden benches. This makes the metal benches feel colder.

Question 34

What does it mean if a substance is aqueous?

Answer 34

Aqueous means that a substance is dissolved in water.

Question 35

A supersonic hedgehog is running around. As he runs the air near his feet heats up. What effect will this have on the gas particles near his toes?

Answer 35

Gas particles move fater at higher temperatures (because thay have more energy), so the gas particles will speed up. The gas will also expand slightly or its pressure will increase.

Question 36

Describe the movement of paticles in a liquid.

Answer 36

The particles in a liquid are randomly arranged and free to move past each other, but tend to stick close together. The particles are constantly moving in random motion.

Question 37

Give some limitations of using particle theory to decribe the movement of particles.

Answer 37

in reality, partilces aren’t slid spheres (they’re atoms, ions or molecules). The particle model dosen’t show the forces between the particles, so there’s no way of telling how stong the forces are.

Question 38

What is condensation?

Answer 38

where a gas is cooled below it’s boiling point

Question 39

what is the main factor that determins the melting point of a substance?

Answer 39

The strength of the forces between the particles.

Question 40

Describe some limitations of using dot and cross diagrams to represent ionic bonding.

Answer 40

Dot and cross diagrams don’t show the structure of the compound, the size of the ions or how the ions are arranged.

Question 41

The structure of compound A is shown below. Describe the structure and bonding in A.

Answer 41

Compound A is an ionic compound which has a giant ionic lattice structure. The ions form a closely packed, regualr lattice held togather by ionic bonds. There are strong electrostatic forces of attraction between the oppositely charged ions, in all directions.

Question 42

The diagram shows the structure of propane. What is the name given to this type of diagram. What is the molecular formula of propane.

Answer 42

Displayed formula - the covalent bonds are single lines between the atoms.
C₃H₈

Question 43

5) The structures of hydrogen and methane are shown below. Which compound would have a higher boiling point?
Explain your answer.

Answer 43

The boiling point of a compound depends on the strength of the intermolecular forces that exist between the molecules. Larger molecules have stronger intermolecular forces, so methane will have a higher boiling point than hydrogen.

Question 44

Give one property of daimond.

Answer 44

hard, high melting point, dosen’t conduct electrity

Question 45

3) Look at the table below. What
physical state will iodine be in at 100°C?

4) Which of the substances in the table on the right will be a gas at 110 °C?

5) A student is investigating the effect of temperature on the physical state of octane.
He heats a sample of octane from 25 °C to 130 °C. Describe the changes that occur in the energy and arrangement of the particles over the course of the experiment.

Answer 45

3) lodine has a melting point of 114 °C, so it will be a solid at 100 °C. This is because the iodine particles won’t have enough energy to break free from their fixed positions and form a liquid.
5) Octane will be a liquid at 25 °C, as this temperature is above its melting point but below its boiling point. As the temperature increases, the particles of octane will gain more energy. This will make the particles move faster, which will weaken the forces that hold the liquid together. Once the temperature reaches the boiling point of octane (126 °C), the particles will have enough energy to break the forces between them. The liquid octane will boil/become a gas.
4) Water is the only substance in the table that will be a gas at 110 °C. In order for a substance to form a gas, it has to be heated above its boiling point. Water has a boiling point of 100 °C, so water will be a gas at any temperatures above 100 °C. Both iodine and octane have boiling points higher than 110 °C, so won’t be gases at that temperature.

Question 46

1) True or False? Fine particles are larger than nanoparticles.

Answer 46

1) True-fine particles are 100-2500 nm and nanoparticles are 1-100 nm.

Question 47

2) What’s the diameter of the smallest possible coarse particle?

Answer 47

2) 2500 nm/2.5 x 10^-6m (Coarse particles have diameters of 2500-10 000 nm.)

Question 48

3) The diameters of some different particles are shown below.
A. 150 nm
B. 0.2 nm

C. 50 nm

D. 1000nm

Which of the particles could be nanoparticles?

Answer 48

3) Nanoparticles have diameters between 1 nm and 100 nm - the only particle with a diameter that falls within this range is the 50 nm particle.

Question 49

4) Silver catalysts work by providing a surface for molecules to react on.
Why might a catalyst containing silver nanoparticles be more effective than one made from a sheet of silver foil?

Answer 49

4) When it’s in the form of nanoparticles, silver has a much higher surface area to volume ratio than when it’s in bulk. So a catalyst made of silver nanoparticles would have a very high surface area for reactions to take place on.

Question 50

Mickey has a cube of cheese. The cube has sides that are 500cm long, and a surface area to volume ratio of 0.012cm^-1. He starts nibbling on the cube. Eventually he is left with a cube with sides that are 5 cm long. What surface area to volume ratio will the nibbled cube have? Explain your answer.

Answer 50

5) The surface area to volume ratio of the nibbled cube will be 1.2 cm^-1. As the side of any cube decreases by a factor of ten, the surface area to volume ratio of the cube will increase by a factor of ten. Mickey’s cube started out with sides of 500 cm, but finished with sides of 5 cm. The side length has decreased by 100 times (500/5 = 100). So, the surface area to volume ratio will increase by the same amount: 0.012 x 100 = 1.2 cm^-1.

Question 51

1) Give one property that a nanoparticle needs if it’s
going to be used in a computer chip.

Answer 51

1) E.g. the nanoparticle needs to be able to conduct electricity.

Question 52

2) Suggest one use for a nanoparticle that has antibacterial properties.

Answer 52

2) E.g. it could be added to fibres that are used to make bandages/surgical masks/wound
dressings. It could be added to deodorants.

Question 53

3) Nanoparticles can be used in cosmetics to make them more effective.
Suggest some possible risks of using nanoparticles in cosmetics.

Answer 53

3) There are quite a few answers you could have given here: e.g. the long-term health impacts of nanoparticles aren’t known. The nanoparticles might damage the environment after they have been washed off the skin. The nanoparticles might be small enough to pass through the skin and remain in the body.

Question 54

4) B company has developed two different types of nanoparticle, A and B. Nanoparticle B has a ball-like structure and is soluble in water. Nanoparticle A is shaped like a thin rod and is slightly soluble in water. Which nanoparticle would be most suitable for delivering drugs to the body cells? Explain your answer.

Answer 54

4) E.g. nanoparticle A would be more suitable for drug delivery, as drugs could be carried within the ball structure and released once the nanoparticle reaches the target cell. Nanoparticle A is also more soluble in water than nanoparticle B, so would be absorbed more easily by the cells/travel more efficiently in the bloodstream.