Chapter 4. States Of Matter

Question 1

What is vapor pressure

Answer 1

The force exerted by gas particles colliding against the walls of a container.

Question 2

What are the assumptions on an ideal gases

Answer 2

-They have zero particle volume
-They have no intermolecular forces of attraction between their molecules
-They are made of particles in rapid and random motion
-The temperature of the gas is directly proportional to the average kinetic energy of the particles
-Collisions between an ideal gas’ particles are perfectly elastic
-Their molecules behave as rigid spheres

Question 3

Why do gases deviate from ideal gas behavior

Answer 3

-particles in a real gas have large molecules (their volume is not zero)
-real gas molecules have intermolecular forces

Question 4

What are the conditions necessary for a real gas to approach ideal gas behavior

Answer 4

-very high temperatures
-very low pressures

Question 5

State Boyle’s law

Answer 5

The product of pressure and volume is a constant provided temperature is constant
pv=constant

Question 6

Sate Charles’ law

Answer 6

The volume is proportional to the temperature provided pressure remains constant
v/T = constant

Question 7

State Gay-Lussac’s law (constant volume law)

Answer 7

Pressure is directly proportional to the temperature as long as volume remains constant
P/T = constant

Question 8

Sate the ideal gas equation

Answer 8

pV = nRT where p(Pa) = pressure, V(m^3) = volume, n = number of moles, R = gas constant(JK^-1mol^-1) and T(K) = temperature

Question 9

How many cubic cm are equal to one cubic metre

Answer 9

1 000 000

Question 10

How do you convert temperature from degrees Celsius to Kelvins

Answer 10

You add 273 to the temperature in degrees

Question 11

Explain what is meant by structure and give the two types of structures

Answer 11

Structure describes the geometrical arrangement of the atoms in space. The two types are giant structure where the atoms form an extended geometrical arrangement and the the other is molecular structure which consists of separate molecules.

Question 12

How do substances allow electricity to pass through them

Answer 12

A current of electricity is a flow of charge. In metals, negative electrons move. In ionic compounds, charged ions move.

Question 13

What is a lattice

Answer 13

A regular arrangement of ions which continues throughout the solid.

Question 14

What is coordination number

Answer 14

This is the number of ions that surround an ion for example in NaCl, the coordination number of sodium is 6 because it is surrounded by 6 chloride ions same for chlorine thus NaCl has a 6,6 coordination number

Question 15

Properties of ionic compounds

Answer 15

1. High melting points because a lot of energy is required to break the strong forces of attraction between positive ions and negative ions.
2. The structure is rigid and brittle
3. They are usually soluble in aqueous solvents
4. In solid state they are non-conductive of electricity because ions are in fixed positions. When molten or in aqueous solution they conduct electricity because ions are free to move from one place to another.

Question 16

Properties of molecular crystals

Answer 16

1. Low melting and boiling points because the Van dear Waal’s forces require very little energy to break because they are weak
2. Non conductor of electricity in any state because no charged particles are present
3. Low solubility in water because iodine molecules can not form hydrogen bonds with water

Question 17

Properties of buckminsterfullerene

Answer 17

1. Low sublimation point turns directly from solid to gas when heated at 600⁰C because of weak van der waal’s forces between its molecules
2. Soft because it requires very little energy to overcome weak van der waal’s forces
3. It is a poor conductor of electricity compared to graphite because the extent of electron delocalization is lower
4. It is more reactive compared to graphite or diamond (reacts with H₂, O₂, F₂, Cl₂ and Br₂) because of the relatively higher electron density in certain parts of the molecules.

Question 18

Properties of diamond

Answer 18

1. Very hard
2. Very high melting point
3. Does not conduct electricity

Question 19

Properties of graphite

Answer 19

1. Graphite is a soft material
2. It has a very high melting point and in fact it breaks down before it melts. This is because of the strong network of covalent bonds, which make it a giant structure.
3. It conducts electricity along the planes of the hexagons

Question 20

Properties of silicone dioxide

Answer 20

1. It is hard due to very strong covalent bonds
2. Has a high melting and boiling point because the very strong silicon-oxygen covalent bonds have to be broken through the structure before melting
3. It does not conduct electricity. There are no delocalized electrons and no ions
4. It is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and silicon or oxygen atoms resulting in overcoming the covalent bonds in the structure.

Question 21

Factors affecting the strength of metallic bonding

Answer 21

1. Number of protons-the more the number of protons the stronger the force of attraction between the positive ions and the delocalized electrons
2. Number of delocalized electrons per atom - the more the stronger
3. Size of the atom - the smaller the stronger

Question 22

Properties of metals

Answer 22

1. High melting points
2. Malleable
3. Ductile
4. Conduct electricity

Question 23

What is vapor pressure?

Answer 23

The pressure caused by the gas particles colliding against the walls of the container.

Question 24

What are the three gas laws?

Answer 24

1. Boyle’s law: The volume of a fixed mass of a gas at a fixed temperature is inversely proportional to the applied pressure.
   pV = constant and P₁V₁ =P₂V₂
2. Charles’ law: The volume of a fixed mass of a gas is directly proportional to the absolute temperature provided the pressure remains constant.
   V/T = constant
3. The “constant volume” law(Gay-Lussac’s law): The pressure of a fixed mass of a gas is directly proportional to the absolute temperature provided its volume remains constant.
   P/T = constant

Question 25

What is the ideal gas equation?

Answer 25

pV = nRT where: p is pressure in Pa(Nm^-2) V is the volume in m³ n is number of moles(mol) R is 8.31JK^-1mol^-1 T is temperature in K

Question 26

What are the basic assumptions of an ideal gas?

Answer 26

1. Ideal gases have zero particle volume. 2. There are no intermolecular forces of attraction between the molecules of an ideal gas. 3. All collisions between molecules of an ideal gas are perfectly elastic. (i.e. There is no loss of kinetic energy during collisions.) 4. The temperature of the gas is related to the average kinetic energy of the molecules. 5. The gas molecules move rapidly and randomly. 6. The molecules of an ideal gas behave as rigid spheres Note: The volume is negligible not necessarily zero

Question 27

Why do real gases deviate from ideal gas?

Answer 27

1. Particles in a real gas have large molecules (their volume is not negligible). 2. Real gas molecules have intermolecular forces

Question 28

What are the conditions necessary for a gas to approach ideal gas behaviour?

Answer 28

Very high temperatures and very low pressures At a very high temperature and a very low pressure, particles have high kinetic energy and are far apart. They have negligible intermolecular forces and particles occupy negligible volume compared with the volume of the container.

Question 29

Explain the limitations of the ideal gas behaviour

Answer 29

The difference between an ideal gas and a real gas are especially noticeable at very high pressures and very low temperatures. Under these conditions: Molecules are close to each other so volume of the molecules is not negligible compared with the volume of the container.There are Van der Waals forces of attractions between molecules. These attractive forces pull the molecules towards each other and away from the walls of the container

Question 30

Properties of ionic compounds

Answer 30

1. High melting points because a lot of energy is required to break the strong forces of attraction between positve ions and negative ions. 2. The structure is rigid and brittle. 3. They are usually soluble in aqueous solvents. 4. In solid state, they are non-conductors of electricity because ions are in fixed positions. When molten or in aqueous solution they conduct electricity because ions are free to move form one place to another

Question 31

Properties of a crystalline solid which is simple molecular

Answer 31

1. Low melting and boiling points because the Van der Waals’forces require very little energy to break because they are weak. 2. Non conductor of electricity in any state becaues no charged particles are present. 3. Low solubility in water because iodine molecules can not form hydrogen bonds with water i.e iodine

Question 32

Properties of carbon fullerene

Answer 32

1. Low sublimation point turns directly from solid to gas when heated at 600oC because of weak van der Waals’ forces between its molecules. 2. Soft because it requires very little energy to overcome weak van der Waals’ forces. 3. It is a poor conductor of electricity compared with graphite because the extent of electron delocalisation is lower. 4. it is more reactive compare with graphite or diamond (reacts with H2, O2, F2, Cl2 and Br2) because of the relatively higher electron density in certain parts of the molecules

Question 33

Properties of a carbon nanotube

Answer 33

1. They have very high tensile strength when a force is applied along the long axis of the cylinder. They can be up to 100 times stronger than steel of the same thickness. 2. They have very high electrical conductivity along the long axis of the cylinder because some of the electrons are delocalised and can move along the cylinder when a voltage is applied. They are superconductors at low temperatures. 3. They have vey high melting points (about 3500oC) because of strong covalent bonds thoughout the structure. 4. Good heat conductance. 5. Multi-walled nanotubes exist, where several concentric tubes lie within each other. The inner tubes can rotate and slide within the outer tube with negligible friction.

Question 34

Properties of a crystalline solid which is a giant molecular

Answer 34

1. It is hard due to very strong covalent bonds. 2. Has a high melting and boiling point because the very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs. 3. It does not conduct electricity. There are no delocalised electrons and no ions. 4. It is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and silicon or oxygen atoms resulting in overcoming the covalent bonds in the structure

Question 35

Properties of graphene

Answer 35

1. Graphene is extremely strong for its mass. (One square hammock made of graphene could support a 4kg cat but would weigh only as much as the cat’s whisker.) 2. Graphene conducts electricity and heat much better than graphite. 3. Graphene is the most chemically reactive form of carbon. Single sheets if graphene burn at very low temperatures and are much more reactive than graphite.

Question 36

Allotropes of carbon

Answer 36

Graphene nanotube fullerene diamond graphite

Question 37

Factors affecting the strength of metallic bonds

Answer 37

1. Number of protons/strength of nuclear attraction. -The more the protons the stronger the force of attraction between the positive ions and the delocalised electrons 2. NUmber of delocalised electrons per atoms-the more the stronger 3. Size of atoms-the smaller the stronger

Question 38

Advantages of recycling

Answer 38

1. less wastes. 2. Cheaper than extracting the metals form ores. 3. Saves energy and ores