Ch 12 - Properties of water Flashcards
How much of the earths land does water cover?
70%
How much does water make up of the human body?
70%
What are 4 physical properties of water
-is a polar molecule-freezes at 0 degrees-exissts in liquis form at 25 degrees-will boil at 100 degrees
Define latent heat
Amount of energy needed to change a substance to a different state.
What are the units for latent heat?
kJ mol-1, and Jkg-1
What is the symbol for latent heat?
L
Define latent heat fusion of water
The amount of energy required to change a fixed amount of water from a solid to a liquid state.
What happens in the process of latent heat fusion of water
The bonds in the ice are broken enabling the water molecules to move around more freely
What are the values for latent heat fusions?
6.02kJ energy is needed to change one mole of water from a solid to a liquid
Define latent heat of vaporisation
Amount of energy hat is needed to change a fixed amount of water from a liquid to a gas.
Does water have a high latent heat?
Yes
Why is it that water has a high latent heat
Strong intermolecular forces between states
What are the values for latent heat vaporisation?
40.7 mol (needed to vaporise one mole of water)
What is perspiration and how does it involve latent heat vaporisation?
Perspiration is a way of removing unwanted heat from the body, .
Define specific heat capacity
The amount of energy needed to raise one gram of substance by one degree
The formula for specfic heat capacity
Q=mct
What is the pattern with high specific heat capacity and energy?
The higher the specific heat capacity the more energy it will need to absorb to raise the temperature.
What is waters specific heat
4.15
What is ethanols specific heat
2.5
Define density
The measure of amount of mass that is contained in a certain volume of substance
Formula for density
d=m/v
What are the units for density?
gcm-3 and kgm-3
What is the official symbol for density?
p
Is ice or liquid water more dense
Liquid water
At what temperature is water at its densist
4 degrees celcius
Does ice float on water
Yes
What does the low density of ice mean?
It expands when frozen
Does pure water conduct electricity
In the very slightest, however is described as a non-conductor
Define self-ionisation
Water molecules reacting slightly with one another to produce a small amount of ions
What bonds so water have?
dispersion and hydrogen
What elements does the hydrogen bind to
Fluorine, nitrogen and oxygen
Explain the strength of hydrogen bonding
No electrons left to shield one side as both of the hydrogens are drawn towards the oxygen, hence water can attract other molecules very closely resulting in a stronger bond.
Do temperatures usually increase or decrease down a group?
increase due to having to break down larger molecules which require more energy.
List ways the hydrogen bonding affects the properties of water
-High melting and boiling points-High latent heat (fusion and vaporisation)-High heat capacity-Ablitlity of water to dissolve other substances
What is water also reffered to as in regards to solubility?
The universale solvent
Are water moelcules polar or non-polar
POlar
What is the rule to do with dissolving
like dissolves like
Explain how water produces hydrated ions
Salt is placed in the water and the water surrounds the postiive and negative ions and pulls them apart
List the behaviour of some substances in water
-some can remain undissolved-ionisation (polar molecules reacting with water to orm ions)-Ionic substances may dissociate-Other polar molecuels such as (suagr and ethanol) can still undergo disscation however the solution will not conduct electricty
Do polar gases dissolve easily in water?
YEs e.g ammoinia gas and hcl gas
Do non-polar gases dissolve easily in water?
NO
What can have an impact on gases dissolving in wate?r
-Temperature: Generally an increase in temperature will decrease solubility
