Compounds and their properties

Question 1

Whats the difference between an ionic compound and a molecular compound?

Answer 1

an ionic compound is made of a cation (positively charged ion) and an anion (negatively charged ion)
- Forms between a metal and a non-metal
- The atoms exchange electrons to fill their valence shell and become more stable
Molecular compounds share electrons instead of one giving another its electrons
- Forms between 2 non-metals

Question 2

What is a formula unit?

Answer 2

A formula unit represents the smallest ratio of an ionic compound
Smallest ratio of a molecular compound is just called a molecule

Question 3

What are some common characteristics of ionic compounds?

Answer 3

Typically solid at room temperature

Dissolve in water and conduct electricity (electrolytes)

Question 4

What are some common characteristics of molecular compounds?

Answer 4

Usually gas at room temperature (can be liquid ex. water)

Most are poor conductors of electricity

Question 5

How much solar energy is absorbed by the atmosphere?

Answer 5

About 70%

Question 6

How do green house gases affect the earth?

Answer 6

Greenhouse gases are particularly good at absorbing head energy radiated off the earths surface

Question 7

What are some common green house gases and their sources

Answer 7

Carbon dioxide - comes from cellular respiration and forest fires, also comes from the combustion of fossil fuels
Water vapour - comes from transpiration and evaporation, also comes from the combustion of fossil fuels
Methane - comes from decaying organic matter, also comes from flatulence of animals
Nitrous oxide - comes from denitrification, also comes from the combustion of fossil fuels and decomposition of chemical fertilizers
Chlorofluorocarbons (CFCs) - no natural source, comes from leaks of and improper disposal of refrigeration gases

Question 8

Why is water a particularly interesting substance?

Answer 8

Water can form hydrogen bonds with itself (weak bonds between the oxygen of one molecule and the hydrogen of another)
- Leads to high boiling point and surface tension
Water is highly polar making it a good solvent
Water also has a high specific heat capacity (the amount of energy required to heat a substance 1 degree celcius)
Water also takes a long time to cool down
Allows for large bodies of water to not experience sudden temperature shifts

Question 9

How does evaporation purify water?

Answer 9

When water evaporates, only the water goes into the air leaving all contaminants behind
A great deal of evaporation happens through transpiration (evaporation of water out of the leaves of plants)

Question 10

What is hydrogen bonding and how does it affect the propertied of water?

Answer 10

The electronegativity difference between oxygen and hydrogen causes the electrons to be closer to the oxygen than the hydrogen making the end that has the oxygen slightly negative and the end that has the hydrogens slightly positive
This results in an attraction between the hydrogen of one molecule and the oxygen of another known as a hydrogen bond
The hydrogen bond allows water to have a high boiling point because more energy is required to split the hydrogen bonds
Since they are attracted to each other, they also have high surface tension leading them to bead.
The hydrogen bonds function as elastic bands which are able to store more energy than a normal substance
Also leads to oil and water not mixing, hydrogen bonding creates an attraction between water that oil cannot break