What does a water molecule look like? What is its shape?
Water is a bent polar molecule. the oxygen is extremely electronegative, so it is partially negative and the hydrogen is partially positive.
How does hydrogen bonding work?
Hyrogen bonding is when the partially negative oxygen is attracted to a partially positive pole in another polar molecule.
Describe hydrogen bonding in liquid, solid and gas forms of water.
1) In liquid, hydrogen bonds are weak, so water is the shape of the container. The molecules have no order, and very transient h bonds.
2) In solid, the low temperature causes very low kinetic energy, so the h bonds are strong enough to hold molecules in place. thThe average distance between each water molecule is larger, so ice is less dense than liquid water.
3) gas - less order, and has very few h bonds because the molecules are moving so fast that they can't get close enough to each other to h bond.
What is the maximum amount of h bonds a water molecule can create?
4. Two to the partially negative O and 2 to the partially positive H.
4 h bonds in ICE, less in other stages
each orient each other so that the opposite charges attract each other.
what are the four emergen tproperties of water that contribute to Earth's fitness for life? What are they caused by?
They are caused by hydrogen bondding and are 1) Cohesion 2) Ability to moderate temperature 3) Insulate Bodies of Water by Floating Ice 4) "Universal" solvent
What is cohesion?
Hydrogen bonding makes water a more structured liquid since each water molecule is linked to multiple other molecules by h bonding. Water molecules cling lightly to each other. This is cohesion.
What is adhesion?
Water clings to another surface that is hydrophilic and polar like itself. For example, tree membranes are very hydrophilic. The wider the cylinder, the worse it is for adhesion, hence why tree trunks are thin and long. Plants have very thin vessels, microscopically thing. This process to bring water up is called transpiration.
What is surface tension?
Measure of how difficult it is to stretch or break the surface of a liquid because the molecules are bonding to the molecules below it, forming a type of layer/film. Pressure needs to be added to go through this film.
How can water moderate temperature?
Water has high specific heat, so it can absorb a lot of heat before it changes temperature. This is again due to hydrogen bonding. Heat is absorbed to break hydrogen bonds instead of to heat the molecules. Because of this,
1)large bodies of water can absorb and store a huge amount of heat.
2) Also conversely, since they are warm, they can warm the air and the surrounding bodies. 3) Ocean temperatures are stable, so marine life can survive.
4) Evaporative cooling helps moderate earth's climate since heat is absorbed by water and then forms rain. Hottest molecules go up as gas.
How does water allow life in oceans?
Water's h bonds in colder weather allow it to have an average distance farther away from each other than in liquid. Therefore, frozen water floats in liquid water, and water freezes from the top down. This helps animals live! Despite freezing temps above water, oceans very rarely freeze and definitely do not freeze entirely.
How is water the solvent of life?
Water is polar. Positive and negative charges of water surround the individual atoms of a molecule that are polar or ionic and separate them from each other. This process is called hydrolysis. Water forms a hydration shell around each atom.
Compounds do not need to be ionic to dissolve in water. Sugar does also
What is hydrophilic
Substances tha tlove wawater. Substances can be hydrophilic without dissolving, like cotton. (this is called a colloid)
what is hydrophobic
Substance that hates water. it is nonionic and non polar and repels water (oils, fats)
How does water dissociate? How often does this happen?
Water has equal concentrations of hydrogyn ions and hydroxide ions.
-increase [H+] of a solution
-donates hydrogion ions (aka protons) - "proton donator"
-HCL --> H+ + Cl (hence strong acid)
-[H+] concentration is 10 ^ (-PH)
so ph of lmeon juice is 2. It has 10^-2 [H+].
Ammonia has a ph of 11. It has 10^-11 [H+]; much smaller.
[OH] is 14-[H+].
Every time you move up on the pH scale is increases ten fold. So if you move two up, it's 10^2 (which is 100 x less/more acidic, etc.)
what are buffers?
Acid base pair that minimize changes in the concentrations of H+ and OH-. Buffers are both hydrogen ion donators and accpetors. H2CO3 (carbonic acid) is a buffer.
The tendency of water molecules to stay close to each other as a result of hydrogen bonding _____.
-keeps water moving through the vessels in a tree trunk
-provides the surface tension that allows leaves to float on water
-acts to moderate temperature
-is called cohesion
-All of the listed responses are correct.
All of the listed responses are correct.
The phenomenon responsible for maintaining the upward movement of water through a vessel is _____.
-heat of vaporization
Adhesion is best described as _____.
-a property of water that helps moderate Earth's temperature
-the clinging of one substance to another substance
-the process by which a crystalline lattice forms
-the process that contributes to the transport of water and dissolved nutrients in plants by causing water molecules to tug on other water molecules
-None of the listed responses is correct.
the clinging of one substance to another substance
Which action would involve the greatest transfer of heat
-raising the temperature of 10 g of ethyl alcohol by 25°C
-condensing 5 g of steam to liquid water
-cooling 10 g of water from 80°C to 40°C
-changing the temperature of 1 g of water from 10°C to 90°C
-evaporating 1 g of water at 25°C
condensing 5 g of steam to liquid water
Sweating has a cooling effect because of water's high
-heat of vaporization
Heat of vaporization
A solution at pH 6 contains _____ than the same amount of solution at pH 8.
-2 times more H+
-4 times less H+
-100 times more H+
-100 times less H+
-4 times more H+
100 times more H+
If you add a weak acid to a buffered solution, what will happen to the pH of the solution? Why?
The pH will stay the same. As the acid donates protons to the solution, the buffer should accept them and remove free protons from the solution.
Coffee has a pH of 5. Lemon juice has a pH of 2. Which has the highest concentration of hydrogen ions? Hydronium ions? Coffee has __x the concentration of protons that lemon juice has.
Lemon juice has the highest protons.
coffee has the higher hydronium ions.
Lemon juice has 10^3 more hydrogen ions, so coffee has .0001 x the amount of hydrogen ions than lemon juice.
Explain why ice floats on water, and how this characteristic helps organisms survive in the cold.
In very cold climates, water molecules do not move much. Therefore, hydrogen bonds can keep molecules together, forming a lattice like structure in ice. In this structure, the average distace between water molecules is larger than in liquid water. therefore, for the same volume of ice versus liquid, the density of the ice is less . Ice feezes from the top down in very cold climates. Once it feezes, the water underneath is actually protected from the freezing conditions above the ice. These two last facts allow organisms can survive in the cold underneath the ice.