Bonding and physical properties

Question 1

Four types of crystal structure:

Answer 1

• ionic
• metallic
• macromolecular (giant covalent)
• molecular

Question 2

Heating a solid

Answer 2

energy is supplied to particles causing them to vibrate in a fixed position. Slightly increases distance between particles causing solid to expand

Question 3

Turning solid to liquid

Answer 3

Energy is needed to weaken the forces between particles. Enthalpy change of melting so when a solid is melting the temp does not increase because the heat energy provided is absorbed as the forces are weakened

Question 4

Heating a liquid

Answer 4

Supply energy to particles causing them to move more quickly - they have more kinetic energy. Particles move a little further apart so liquids also expand on heating

Question 5

Turning liquid to gas

Answer 5

Enough energy is needed to break the intermolecular forces. Gas consists of particles that are far apart and move independently. Energy needed is called the enthalpy change of vaporisation. No temp change during process

Question 6

Heating a gas

Answer 6

Particles gain kinetic energy and move faster. Get much further apart so gases expand a great deal on heating

Question 7

Ionic Crystals

Answer 7

Strong electrostatic attractions between oppositely charged ions. They have high melting points due to strong electrostatic attractions which extend throughout the structure. Require alot of energy to break in order for the ions to move apart from each other.

Question 8

Metallic Crystals

Answer 8

lattice of positive ions embedded in a delocalised sea of electrons. High melting temp is a result of strong metallic bonds

Question 9

Molecular Crystals

Answer 9

Covalent bonds hold molecules together but do not act between them.

• soft and break easily
• low melting temp and sublimes readily to form gaseous iodine molecules
• do not conduct electricity as no charged particles to carry charge

Question 10

Macromolecular Crystals

Answer 10

Covalent bonds extend throughout the compound and have a giant structure - high melting points.

Question 11

Diamond

Answer 11

Giant structure of pure carbon with covalent bonds present.

• very hard material
• very high melting temp (over 3700K)
• does not conduct electricity as no free charges particles

Question 12

Types of intermolecular forces

Answer 12

van der waals - act between all atoms
dipoledipole - act between molecules with permanent dipoles
hydrogen - highly electronegative atoms and hydrogen atoms are bonded together