How bonding and structure are related to the properties of substances

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The Three States of Matter

The three states of matter are solid, liquid and gas.
In a solid, particles are very close together in a regular arrangement and vibrate about fixed positions.
In a liquid, particles are close together and randomly arranged, and they move around each other.
In a gas, particles are far apart and randomly arranged, and they move quickly in all directions.
The simple particle model represents particles as small solid spheres.
A substance can usually exist in all three states depending on temperature (and pressure).

Changes of State

Melting is a solid changing into a liquid; freezing is the reverse, liquid to solid.
Melting and freezing occur at the melting point; boiling and condensing occur at the boiling point.
Boiling is a liquid changing into a gas throughout the liquid, forming bubbles.
Evaporation is a liquid changing into a gas only at the surface, and it occurs over a range of temperatures below the boiling point.
Condensation is a gas changing into a liquid on cooling.
Sublimation is a solid changing directly into a gas (e.g. iodine, solid carbon dioxide); the reverse is called deposition or desublimation.
Changes of state are physical changes: the particles themselves remain the same, only the forces between them change, and the change is easily reversed.

The state changes

Energy and Interconversions

The amount of energy needed to change state depends on the strength of the forces between the particles.
The stronger the forces between particles, the more energy is needed to overcome them, so the higher the melting point and boiling point.
When a substance is heated, particles absorb thermal energy and convert it into kinetic energy, so they vibrate or move more.
On a heating or cooling curve, horizontal sections show a change of state where temperature stays constant as energy is absorbed or released.
The sloped sections show the substance heating up or cooling down in a single state.
The interconversion of states can be shown with a reversible arrow: ⇌.

Predicting Physical State

Below the melting point, a substance is a solid.
Between the melting point and the boiling point, a substance is a liquid.
Above the boiling point, a substance is a gas.
For example, a substance with melting point −7 °C and boiling point 59 °C is a liquid at 20 °C and a gas at 100 °C.
Individual atoms do not have the bulk properties of the material they make up.

State Symbols

State symbols show the physical state of each substance in a chemical equation.
(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water).
State symbols are written after each formula in brackets.
Example: CuCO₃(s) + 2HCl(aq) → CuCl₂(aq) + CO₂(g) + H₂O(l).
Aqueous means the substance is dissolved in water to form a solution.

Properties of Ionic Compounds

Ionic compounds form giant ionic lattices with strong electrostatic forces of attraction in all directions between oppositely charged ions.
They have high melting and boiling points because a large amount of energy is needed to overcome the many strong electrostatic forces.
The greater the charge on the ions, the stronger the electrostatic forces and the higher the melting point (e.g. MgO has a higher melting point than NaCl).
Solid ionic compounds do not conduct electricity because the ions are in fixed positions and cannot move.
When molten or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry charge.

Properties of Small Molecules

Substances made of small molecules are usually gases or liquids with relatively low melting and boiling points.
They have strong covalent bonds between the atoms within each molecule, but only weak intermolecular forces between molecules.
When a simple molecular substance melts or boils, it is the intermolecular forces that are overcome, not the covalent bonds.
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
Small molecular substances do not conduct electricity because there are no free ions or electrons to carry charge.

Polymers

Polymers consist of very large molecules made by linking many small molecules called monomers.
The atoms in polymer molecules are linked by strong covalent bonds.
The intermolecular forces between polymer chains are relatively strong compared with those between simple molecules.
Because of these stronger intermolecular forces, polymers are usually solids at room temperature.
Examples include polythene and poly(chloroethene), commonly known as PVC.

Monomers joining to form a polymer

Giant Covalent Structures

Giant covalent structures are solids with very high melting points, made of many non-metal atoms bonded by strong covalent bonds.
All the atoms are linked by strong covalent bonds, and these bonds must be overcome to melt or boil the substance.
Examples include diamond, graphite and silicon dioxide (silica).
Diamond: each carbon atom bonds to four others in a tetrahedron; it is extremely hard, has a very high melting point, and does not conduct electricity.
Graphite: each carbon atom bonds to three others in layers of hexagons, leaving one free electron per carbon atom, so graphite conducts electricity and is soft and slippery.
Silicon dioxide is made from silicon and oxygen atoms and also has a giant covalent structure.

Properties of Metals and Alloys

Metals have giant structures with strong metallic bonding – the attraction between positive metal ions and negative delocalised electrons.
Most metals have high melting and boiling points because the metallic bonds are strong and need lots of energy to break.
Pure metals are malleable because the atoms are arranged in layers that can slide over each other when a force is applied.
An alloy is a mixture of two or more metals, or a metal with a non-metal such as carbon (e.g. steel is iron and carbon).
Alloys are harder than pure metals because the different-sized atoms distort the layers, making it more difficult for the layers to slide over each other.
Metals are good conductors of electricity because the delocalised electrons are free to move through the structure and carry charge.
Metals are good conductors of thermal energy because the delocalised electrons transfer energy through the structure.

In an alloy, atoms of a different size (Element Y) are scattered among the host metal's atoms (Element X), distorting the regular layered arrangement that a pure metal has.

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1.Which of the following is the name of the change of state when a liquid changes into a solid?
Easy
- Acondensation
- Bevaporation
- Cfreezing
- Dmelting
2.Substance Y melts at -101 °C and boils at -35 °C. What is the state of substance Y at -110 °C?
Easy
- Asolid
- Bliquid
- Cgas
- Daqueous
3.Substance Z has a melting point of -7 °C and a boiling point of 59 °C. What is the state of Z at 0 °C and at 100 °C?
Medium
- Asolid at 0 °C and gas at 100 °C
- Bgas at 0 °C and liquid at 100 °C
- Cliquid at 0 °C and solid at 100 °C
- Dliquid at 0 °C and gas at 100 °C
4.Substances exist as solids, liquids or gases. What change of state occurs at Y?
Medium
- Amelting
- Bfreezing
- Cboiling
- Dcondensation
5.A balloon is filled with helium gas. What is true about the gas particles inside the balloon?
Medium
- AThey have little energy
- BThey vibrate in fixed positions
- CThey fall to the bottom of the balloon
- DThey move in random directions
6.Which of the following is not a chemical change?
Medium
- AIron railings becoming rusty
- BBurning a piece of wood
- CNeutralising an acid with alkali
- DDissolving salt in water
7.The three states of matter are solid, liquid and gas.
Easy
True or false?
8.In a solid, the particles are arranged randomly and move quickly in all directions.
Easy
True or false?

Thêm câu hỏi

9.For a pure substance, the melting point and freezing point are the same temperature.
Easy
True or false?
10.What is the state symbol for a substance dissolved in water?
Easy
- A(s)
- B(l)
- C(g)
- D(aq)
11.Which statement about ionic compounds is correct?
Medium
- AThey conduct electricity when solid because electrons are free to move.
- BThey have low melting points because the ions are small.
- CThey conduct electricity when molten or dissolved because the ions are free to move.
- DThey are made of molecules held together by weak intermolecular forces.
12.Which statement about simple molecular substances is correct?
Medium
- AThey have high melting points because covalent bonds are strong.
- BThey conduct electricity when molten because electrons are free.
- CThey have low melting points because the intermolecular forces are weak.
- DThey have low melting points because the covalent bonds break easily.
13.Which statement about polymers is correct?
Medium
- AThey are gases at room temperature because they have weak intermolecular forces.
- BThey are solids at room temperature because the intermolecular forces between polymer chains are relatively strong.
- CThey have low melting points because they are made of small molecules.
- DThey conduct electricity because they have delocalised electrons.
14.Which statement about giant covalent structures is correct?
Medium
- AThey have low melting points because they are made of small molecules.
- BThey have high melting points because they have many strong covalent bonds.
- CThey conduct electricity because they have free electrons.
- DThey are soft and slippery because the layers slide over each other.
15.Why are alloys harder than pure metals?
Medium
- AAlloys have stronger metallic bonds than pure metals.
- BAlloys have atoms of different sizes that distort the layers, making it harder for them to slide.
- CAlloys have delocalised electrons that are less free to move.
- DAlloys have weak intermolecular forces between the atoms.
16.Why do metals conduct electricity?
Medium
- AThey have free ions that can move and carry charge.
- BThey have delocalised electrons that can move and carry charge.
- CThey have weak intermolecular forces between the atoms.
- DThey have strong covalent bonds between the atoms.
17.Which of the following statements about ionic compounds are correct? (select all that apply)
Medium
- AThey have high melting points because of strong electrostatic forces between oppositely charged ions.
- BThey conduct electricity when solid because their ions are free to move.
- CThey form giant ionic lattices with regular arrangements of ions.
- DThey conduct electricity when molten or dissolved in water because their ions can move.
- EThey are made of small molecules held together by weak intermolecular forces.
18.Which of the following statements about simple molecular substances are correct? (select all that apply)
Medium
- AThey have low melting and boiling points.
- BThey conduct electricity when molten.
- CThey have strong covalent bonds between the atoms within each molecule.
- DThey have weak intermolecular forces between the molecules.
- EThey are usually solids at room temperature.
19.Match each state symbol to its meaning.
Medium
- (s)
- (l)
- (g)
- (aq)
- solid
- liquid
- gas
- aqueous
20.Match each change of state to its correct description.
Medium
- melting
- boiling
- freezing
- condensation
- solid to liquid
- liquid to gas
- liquid to solid
- gas to liquid
21.Arrange the steps to show the changes of state as a solid is heated until it becomes a gas.
Medium
- solid
- liquid
- gas
22.Arrange the states of matter in order of increasing distance between particles.
Medium
- solid
- liquid
- gas
23.Match each change of state to the correct description.
Medium
- Melting
- Freezing
- Evaporation
- Condensation
- A solid changes into a liquid
- A liquid changes into a solid
- A liquid changes into a gas at the surface, below the boiling point
- A gas changes into a liquid
24.Which of the following are correct about the simple particle model of matter? (select all that apply)
Medium
- AParticles are represented by small solid spheres
- BThe model includes forces between the particles
- CThe model represents all particles as the same, regardless of their chemical identity
- DThe particles are represented as inelastic spheres
- EThe model distinguishes between atoms, ions and molecules
25.Arrange the following processes in order of increasing energy required to overcome the forces between particles, starting with the least energy.
Easy
- Melting a simple molecular substance
- Boiling a simple molecular substance
- Melting a giant ionic compound
- Melting a giant covalent structure
26.A substance has a melting point of 80 °C and a boiling point of 218 °C. In which state is the substance at 100 °C?
Medium
- ASolid
- BLiquid
- CGas
- DAqueous
27.When a simple molecular substance boils, the covalent bonds within its molecules break.
Easy
True or false?
28.Which statement best explains why diamond does not conduct electricity but graphite does?
Hard
- AIn diamond all outer electrons are held in covalent bonds, while in graphite each carbon atom has one delocalised electron that can move
- BDiamond has a giant covalent structure while graphite has a simple molecular structure
- CGraphite has free ions that carry charge, while diamond has free electrons
- DDiamond has weak intermolecular forces that prevent charge flow, while graphite has strong covalent bonds
29.Match each substance to its structure type.
Medium
- Sodium chloride
- Carbon dioxide
- Diamond
- Poly(ethene)
- Giant ionic lattice
- Simple molecular
- Giant covalent
- Polymer
30.Which statement explains why metals are good conductors of electricity?
Hard
- ADelocalised electrons are free to move through the structure and carry charge
- BPositive metal ions are free to move through the structure and carry charge
- CThe layers of metal atoms can slide over each other
- DMetals have weak intermolecular forces between their atoms
31.Which of the following statements about alloys are correct? (select all that apply)
Medium
- AAlloys are mixtures of two or more metals or a metal and a non-metal
- BAlloys are harder than pure metals because atoms of different sizes distort the layers
- CAlloys have lower melting points than pure metals because the bonds are weaker
- DAlloys contain atoms of different sizes which prevent layers from sliding easily
- EAlloys are pure metals with a regular arrangement of identical atoms
32.Which of the following is a property of a typical simple molecular substance?
Medium
- AIt has a high melting point because of strong covalent bonds
- BIt conducts electricity when molten
- CIt has a low boiling point because of weak intermolecular forces
- DIt is a giant lattice of ions
33.Which of the following statements about polymers is correct?
Medium
- APolymers are gases at room temperature because they have weak intermolecular forces
- BPolymers are solids at room temperature because the intermolecular forces between polymer chains are relatively strong
- CPolymers consist of small molecules with low melting points
- DPolymers conduct electricity because they have delocalised electrons
34.A label on a bottle of drinking water states: calcium ions 60 mg per 1000 cm³. Calculate the mass of calcium ions in 250 cm³ of this water.
Medium
- A15 mg
- B60 mg
- C240 mg
- D0.24 mg
35.A solid ionic compound is tested for electrical conductivity in three different conditions. In which condition will it conduct electricity?
Medium
- AWhen molten
- BWhen solid
- CWhen frozen
- DIt never conducts
36.A substance has a melting point of 122 °C and a boiling point of 249 °C. A student places a sample in a beaker of hot water at 80 °C. What happens to the substance?
Hard
- AIt remains a solid and does not melt
- BIt melts to form a liquid
- CIt boils and forms a gas
- DIt sublimes directly to a gas
37.Which statement explains why sodium chloride has a much higher melting point than iodine?
Medium
- ASodium chloride has a giant ionic lattice with strong electrostatic forces in all directions, while iodine has weak intermolecular forces between molecules
- BSodium chloride has weak intermolecular forces while iodine has strong covalent bonds
- CSodium chloride has strong covalent bonds while iodine has a giant covalent structure
- DSodium chloride has delocalised electrons while iodine has free ions
38.A substance conducts electricity when solid and has a very high melting point. It is also malleable. Which type of structure does it have?
Hard
- AMetallic
- BSimple molecular
- CGiant covalent
- DIonic
39.A substance is a solid at room temperature, does not conduct electricity, and has a very high melting point. It is made from a non-metal element. Which type of structure is it most likely to have?
Hard
- AGiant covalent
- BSimple molecular
- CIonic
- DMetallic
40.A polymer is heated and eventually melts. Which forces are overcome when the polymer melts?
Hard
- AThe intermolecular forces between the polymer molecules
- BThe covalent bonds between the atoms within the polymer molecules
- CThe ionic bonds between the polymer molecules
- DThe metallic bonds between the polymer molecules
41.A gas is cooled and starts to form a liquid at 10 minutes. It is completely liquid at 25 minutes. Calculate the number of minutes it took from the gas first starting to form a liquid until the substance was completely liquid.
Medium
42.Complete the sentence about a heating curve.
Easy
The ____ lines on the graph show interconversions between the three states of ____.
43.Complete the sentence about freezing point.
Easy
Freezing point is the same as ____ point.
44.Name the change of state when a solid changes directly into a gas.
Easy
45.Name the type of bonding in a metal.
Easy
46.Describe how the movement and arrangement of water particles changes when water is cooled from 10 °C to -10 °C.
Hard
47.A student puts some solid wax into a test tube and heats it with a Bunsen burner. Name the interconversion of state that happens and describe how the student could reverse this change.
Hard
48.A teacher reacts sodium with chlorine to make the compound sodium chloride. Are the properties of sodium chloride the same or different to sodium and chlorine? Give a reason for your answer.
Hard
49.Explain why ionic compounds conduct electricity when molten or dissolved in water but not when solid.
Hard
50.Explain why simple molecular substances have low melting and boiling points.
Hard
51.A gas is cooled and starts to form a liquid at 10 minutes. It is completely liquid at 25 minutes. Calculate the number of minutes it took from the gas first starting to form a liquid until the substance was completely liquid.
Medium
- A16 minutes
- B15 minutes
- C17 minutes
- D14 minutes

Thẻ ghi nhớ

What are the three states of matter?

Solid, liquid and gas.

In the simple particle model, how are particles represented?

As small solid spheres.

How are particles arranged and how do they move in a solid?

Regular arrangement; they vibrate about fixed positions.

How are particles arranged and how do they move in a liquid?

Randomly arranged; they move around each other.

How are particles arranged and how do they move in a gas?

Randomly arranged and far apart; they move quickly in all directions.

What is melting?

The change from solid to liquid, occurring at the melting point.

What is freezing?

The change from liquid to solid, occurring at the same temperature as melting.

What is boiling?

The change from liquid to gas, occurring at the boiling point.

What is condensation?

The change from gas to liquid on cooling.

What is sublimation?

The direct change from solid to gas, e.g. iodine or solid carbon dioxide.

What is the relationship between the strength of forces between particles and melting/boiling points?

The stronger the forces between the particles, the more energy needed to overcome them, so the higher the melting and boiling points.

What state symbols are used in chemical equations?

(s) solid, (l) liquid, (g) gas, (aq) aqueous solution.

Why do ionic compounds have high melting and boiling points?

They have giant ionic lattices with strong electrostatic forces of attraction between oppositely charged ions in all directions, requiring lots of energy to overcome.

When can ionic compounds conduct electricity?

When molten or dissolved in water, because the ions are free to move and carry charge.

Why do simple molecular substances have low melting and boiling points?

They have weak intermolecular forces between molecules, which require little energy to overcome; the strong covalent bonds within molecules do not break.

What is the difference between covalent bonds and intermolecular forces in a simple molecule?

Covalent bonds are strong forces between atoms within a molecule; intermolecular forces are weak forces between molecules.

Why do polymers have higher melting points than simple molecules?

The intermolecular forces between polymer chains are relatively strong, so polymers are usually solids at room temperature.

Why do giant covalent structures have very high melting points?

All atoms are linked by strong covalent bonds in a giant lattice, and these bonds must be overcome, requiring lots of energy.

Name three examples of giant covalent structures.

Diamond, graphite and silicon dioxide (silica).

Why are metals malleable?

The atoms are arranged in layers that can slide over each other when a force is applied.

Why are alloys harder than pure metals?

Alloys contain atoms of different sizes, which distort the layers and make it more difficult for the layers to slide over each other.

Why do metals conduct electricity?

They contain delocalised electrons that are free to move through the structure and carry charge.

Why do metals conduct thermal energy?

Delocalised electrons transfer energy through the structure.

What is the structure of a metal?

A giant lattice of positive metal ions with delocalised electrons; strong metallic bonding holds the structure together.

How can you predict the state of a substance from its melting and boiling points?

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

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