Polarity
Physical Properties
Water & Life
Capillary Action
Can It H-Bond
100
These types of molecules are insoluble in water.
What are nonpolar molecules?
100
These two properties of water work together to transport water through plant stems.
What are cohesion & adhesion?
100
This property of water allows aquatic animals to spend less energy keeping themselves upright/floating.
What is buoyancy?
100
Plants have evolved xylem and roots that are both _______ to better attract water through them.
Polar
100
These are the three elements capable of bonding unequally enough with hydrogen to form H-bonds.
What are oxygen, nitrogen, and fluorine?
200
Water is polar, due to __________ bonds sharing electrons __________, creating oppositely charged ends.
What is covalent & unequally?
200
This property of water allows it to be used for transporting nutrients quickly and easily.
What is fluidity?
200
Scientists believe that this property of water was the main contributing factor to the evolution of early ocean life.
What is thermal stability?
200
Water travels around plant cells via the ________ pathway.
What is apoplastic?
200
A hydrogen bond is not a true bond, but rather a different type of ____________ force.
What is intermolecular?
300
This property of oxygen allows water to form hydrogen bonds.
What is electronegativity?
300
This property of water makes it the optimal medium for chemical reactions inside of cells.
What is solvent ability?
300
This property of water caused many aquatic animals to develop insulated blubber or fur.
What is thermal conductivity?
300
Water travels through plant cells via small openings called ________________ in the ________ pathway.
What are plasmodesmata & symplastic?
300
Hydrogen bonds are not intramolecular forces because they don't involve the sharing or transfer of this subatomic particle.
What are electrons?
400
IB STYLE:
Draw two water molecules hydrogen-bonded together. Label the intermolecular and intramolecular forces, and the partial charges on each molecule. [4]
1 mark - two water molecules are drawn as H2O with O in the middle
1 mark - the bonds between O-H inside each molecule are labeled "covalent" or "intramolecular"
1 mark - the bond between O-H of neighboring water molecules is labeled "H-bond" or "intermolecular", AND is visually distinct from the covalent bond
1 mark - the partial charges are correctly indicated with the negative around the oxygen AND in proper notation (either with an arrow or delta symbol)
400
IB STYLE:
List and briefly describe three ways water is necessary for the human body. [3]
ANY OF THE FOLLOWING (1 each)
1) Water is the main component of blood, which transports nutrients (fluidity)
2) Water is the main component of cytoplasm, which allows metabolism to occur in cells
3) Water is the main component of our waste, which allows it to dissolve and be expelled easily
4) Water between our cells and in tissues allows nutrients, chemical messages, etc... to be transported between cells
400
Describe one advantage and one challenge of living in the water. [2]
Advantages (1 each)
1) buoyancy - keeps up body weight, no wasting energy
2) fluidity - allows very fast motion OR transport of sexual materials OR transport of filter feeder nutrients
3) thermal stability - allows long-term stable evolution
Disadvantages (1 each)
1) thermal conductivity - causes body heat to be lost quickly
2) viscosity - increases drag and makes movement more energetically expensive
3) opacity - reduces visibility, especially at very low depths and reduces capacity for plant life
4) density - makes hunting difficult as organisms need to control how well they sink or float
400
An experiment is conducted to test the speed at which water climbs various polar tubes. Three tubes are used - one 0.1 mm diameter, one 0.5 mm diameter, and one 1 mm diameter of the same length. Students time how long water takes to travel up each one.
Predict the results of the experiment and justify your prediction by discussing one property of water. [2]
1 mark - prediction of the 0.1 mm tube having the fastest climb time
1 mark - justification of prediction by discussing that increased surface area between the water and tube allows for more adhesive attraction
400
The molecule below can form this many H-bonds at once.
What is three?
500
IB STYLE
Surface tension is the property of water that results in large splashes or painful "splats" if a diver has improper technique.
A) Draw a diagram of surface tension [2].
B) Explain what forces result in surface tension [2].
A) 1 mark - diagram includes a body of water and some depiction of water molecules making it up
1 mark - water molecules at the surface are shown hydrogen bonding to each other
B) 1 mark - identification of hydrogen bonds as the intermolecular forces creating surface tension
1 mark - some connection of these forces to the requirement to "break" the bonds to enter the water (requires energy, causes resistance, etc...)
500
IB STYLE
A) Draw the most energetically optimal shape for a fish. [1]
B) List two properties of water and discuss how the fish's shape helps it adapt to them. [2]
A) 1 mark - drawing is football shaped (can include fins but no limbs)
B) 2 marks - buoyancy, fish do not expend energy maintaining limbs and rely on water to carry weight
2 marks - viscosity, fish are shaped to reduce drag from pushing through water
500
IB STYLE:
Outline the role of water in the origin of early life [3].
ANY THREE OF THE FOLLOWING (1 point each)
1) water provided a thermally stable environment, allowing things to evolve and change without disruption in the ocean
2) water allowed nutrients, amino acids, etc... to be dissolved, giving them a place to interact and combine into more complicated molecules and eventually cells
3) water's solvency made it the perfect medium for early cells (cytoplasm is mostly water)
4) water was brought to Earth via asteroids
5) water (as steam) provided thermal stability to Earth's atmosphere and helped cool it down after the extremely hot and firy collisions that formed the planet
6) water provided a fluid medium for sperm and other reproductive materials to travel, allowing for early methods of sexual reproduction
500
IB STYLE:
Draw and label a model of nutrient transport and capillary action in plants. Label the role of water at each relevant location. [4]
ANY COMBINATION OF THE FOLLOWING (1 point each) ((NUMBER ONE MUST BE INCLUDED))
1) Water shown flowing up through the plant and out into the atmosphere using arrows or other means
2) Zoomed-in view of molecular interactions between polar plant xylem and water, labeled "capillary action" or "cohesion"
3) Zoomed-in view of plant cells with water in them
4) Zoomed-in view of water flowing into the gaps between plant cells and through cells themselves, labeled symplastic pathway
5) Zoomed-in view of water flowing around plant cells, labeled apoplastic pathway
6) Diagram of water pulling itself up the xylem (the surface water pulling the water below it upwards) labelled adhesion
7) Diagram of partial charges on water relating them to partial charges of other water molecules
8) Diagram of partial charges on water relating them to the partial charges of xylem walls, roots, or soil
500
IB STYLE:
Distinguish between a polar molecule and an ion. [2]
ANY TWO OF THE FOLLOWING:
1 mark - an ion has an overall molecule charge due to having extra or less electrons than normal
1 mark - a polar molecule is a covalently bonded molecule that shares electrons unequally, causing partial charges rather than an overall molecular charge
1 mark - polar molecules result from covalent bonds being unequal, ions result from ionic bonds