2.2 Properties of compounds

Question 1

2.2.1 States of matter

Solid, liquid, gas matter

Answer 1

• The amount of energy needed to change states depend on the strength of the forces between particles of substance
• the stronger the forces between the particles, the higher the melting point and boiling point of the substance.
• Solid: vibrate in a fixed position, particles touching, low in energy, organised in a regular arrangement
• Liquid: slighly further apart, can slide over each other, vibrating more, moderate amount of energy
• Gas: arranged randomly, far apart, bounce/moves quickly, high amount of energy.

Question 2

2.2.2 State symbols

State symbols

Answer 2

solid (s), liquid (l), aqueous (aq) and gaseous (g).

• Solids – most metals and insoluble compounds (like silver chloride and lead chloride).
• Liquid – water, ethanol and molten ionic compounds.
• Aqueous – anything in solution e.g. sodium chloride dissolved in water
• Gaseous – elements that are gaseous at room temperature include the noble gases, fluorine, oxygen and nitrogen

Question 3

2.2.3 Properties of ionic compounds

Properties of ionic compounds

Answer 3

• high MP and BP because of the large amounts of energy needed to break the many strong bonds
• when melted/dissolved, ionic compounds can conduct electricity - *ions are free to move so charge can flow. *

Question 4

2.2.4

Properties of small molecules

simple covalent molecules

Answer 4

• low MP and BP due to weak intermolecular forces
• intermolecular forces increase with the size of molecules (large molecules have high MP/BP)
• does not conduct electricity, doesn’t have charged particles
• gases/liquid at room temp (due to low MP/BP)

Question 5

2.2.5 Polymers

Polymers

Answer 5

• long chain of molecules joined together by covalent bonds
• made up of repeating units (monomers) joined together by covalent bonds
• High MP/BP – due to the strong covalent bonds which need a lot of energy to overcome
• Solid at room temp – due to the high melting and boiling point

Question 6

2.2.6 Giant covalent structures

Diamond

Answer 6

• 4 covalent bonds per carbon atom
• very strong covalent bonds - strong intermolecular forces
• high MP and BP - large amounts of energy needed to break bonds
• does not conduct electricity - no free electrons

Question 7

2.2.6 Giant covalent structures

Graphite

Answer 7

• 3 covalent bonds per carbon atom
• high MP to breaks bonds, strong intermolecular forces
• conducts electricity (has delocalised electrons per carbon atom)

Question 8

2.2.6 Giant covalent structures

Silicon dioxide

Silica

Answer 8

High MP, high BP – due to the strong covalent bonds which need a lot of energy to overcome

Unable to conduct electricity – as they do not contain moving charged particles.

Question 9

2.2.7 Properties of metals and alloys

Properties of metals and alloys

Answer 9

Alloys: mixture of two or more elements/metals. Distorted layers so the layers cannot slide, making it stronger and harder
Metals: has high MP, conducts heat and electricity (through delocalised electrons), high density, malleable.

Question 10

2.2.8 Metals as conductors

Metals as conductors

Answer 10

good conductors of electricity - the delocalised electrons in the metal carry electrical charge through the metal.
good conductors of thermal energy - energy is transferred by the delocalised electrons.