`Outcome 1- Water/ Ionic equations Flashcards
Properties of water
- High melting and boiling points of water compared wit h similarly sized molecular substances.
- Expands when frozen
- Relatively high latent heat value for fusion and evaporation
- High specific heat capacity
- Ability to dissolve other substances
Explain how the properties of water can be explained by the nature of the intermolecular forces between water molecules
The existence of hydrogen bonding between water molecules allows it be a good solvent for other polar substances as well as many ionic substances
Why is water different from most liquids with respect to its density in the solid and liqud states
Its solid form is less dense than its liquid form. The molecules are arranged in a more structured hexagonal way. This means ice floats on water and that water freezes from the surface down.
What is latent heat
Measures the amount of energy required to change the state of a given amount of substance
What is specific heat capacity
The amount of energy needed to raise the temperture of one gram of the substance by one degree celcius.
How is water unique to latent heat and SHC
it has the ability to absorb large amounts of heat energy with only a minimal increase in temperture. The higher the SHC is the more energy it must absorb to raise its temp
Why would life not exist if ice was denser than water
If Ice were denser than water, bodies of water would freeze solid during winter and the aquatic life would die.
How does “like dissolves like” explain that- Potassium chloride dissolves in water
Potassium chloride is ionic and water is Polar
How does “like dissolves like” explain that- Ammonia dissolves in water
Ammonia and water are both polar
How does “like dissolves like” explain that- Methane is insoluble in water
Methane is non polar where as water is polar
Latent heat of fusion
The change from solid to liquid
Latent heat of vaporisation
The change from liquid to gaseous
Symbol for latent heat is
l and units are kjmol-1 and jkg-1
Latent heat of fusion of water is
6.02kj mol-1
How much energy is needed to raise 250ml of water from 20C to 100C?
250x 4.18x (100-20)
=83 kj or 8300j or 4.2x 10^3 j
Specific heat capacity of water
4.18jg-1
Is water electrically neutral?
Pure does conduct electricity very slightly, however the amount is so tiny, it is still viewed as a non conductor.
Water molecules can react with each other. this is called SELF IONISATION OF WATER
Hydrophillic
They are polar compounds so they are strong enough to break the cohesive hydrogen bonds. This dissolves with the water
Hyrdro phobic
Cannot overcome the cohesive nature of water.
These molecules are non polar and cannot dissolve
Capillary action
When water molecules are molecules are attracted to other water molecules by cohesion (Attraction of water) This causes water molecule to go up a glass straw
Using water a solvent
Industrial Applications
Biological Applications
Domestic Applications
Two reactions when mixing solutions
Nuetralisation and precipation
Dissociation is
Ionic compounds dissolving in water
Ionisation is
Covelant compounds dissolving in water
Equation for self ionisation of water
H2O + H2O -> H3O+ + OH-
