A1.1 (Water) Flashcards
Why is water inorganic
Doesn’t have carbon. Organic stuff needs hydrogen AND carbon
Why can’t you drink ocean water while swimming?
It will make you dehydrated due to the high salt content
Why is water the medium of life?
We believe that life has originated in water.
- Where the cell membrane was formed
- Where the solutes dissolved
- Where the chemical reactions occurred
Implication: It gave way to prokaryotes. Life came from water
How much water is found in Earth? And where is most of them found? (edit percentage)
70%, most in oceans
Define covalent bond
Electron sharing
Why is water polar?
-
Unequal attraction/sharing of electrons oxygen has 8 electrons > the two hydrogen atoms have 1
-> due to oxygen’s stronger pull on the electrons
Outline the different bonds between water molecules (intermolecular + intramolecular)
If its just inside the molecule (i.e. between the oxygen and hydrogen atoms), it’s covalent (stronger),
if it’s between more than 1 molecule (intermolecular bond) it’s hydrogen bond
Explain what are hydrogen bonds
Definition: A type of bond between a hydrogen atom and an electronegatic (i.e. negatively-charged) atom such as oxygen
- This is due to the law of attraction as hydrogen is positively-charged.
Outline the biological properties of water
cohesion, adhesion, and solvent properties
Explain the cohesion of water and its effect on water
water-to-water molecule attraction (intramolecule — my own term)
- one hydrogen bond weak but many strong
Effect: More uniform motion — There would be surface tension when in contact with non-polar substances or — causing droplets (so they could have as less surface area/least “touching” with non-polar substances as possible). Because of the cohesive forces, the drop has a thin membrane.
Explain surface tension
tendency of liquid surfaces to be smallest VA when in contact with non-polar substances due to cohesion’s hydrogen bonding
(think of a drop of water on non-polar cloth for example)
How does cohesion affect the transport of water in plants?
Pulling forces caused by the evaporation of water from the leaves make the water moves upwards
-> And I think they’ll all go up in a somewhat uniform fashion because of the cohesive forces
Explain adhesion of water
- The attraction between water and polar surfaces (polar-polar attraction)
Adhesion and drinking from a straw
The water sticks to the polar surface (adhesion ) and make the capillary action to work
Describe capillary action relating to adhesion
(Adhesion): Water is attracted to polar surfaces, and the xylem vessel in the plants are polar.
- THEREFORE (implication): the water will follow the polar surface (xylem vessel) up and go to the parts of the plant that need water.
Side note: The law of attraction is not between non-polar and polar substances. It is only about polar and polar substances (because the law pertains to negative and positive charges)
Define “meniscus” (DOUBLE CHECK)
The shape of the “outer membrane” (or “outer layer of water”)
What determines the shape of the meniscus?
Convex: cohesive forces > adhesive forces (non-polar surface/substance)
(the molecules stick more together than on the surface)
Concave: cohesive forces < adhesive forces (polar)
(the molecules stick more to the surface than one another — most likely the surface will be wet bc its polar)
1 - OSC 1 - bs
Define tetrahedral
“4 heads”
How is tension created in the xylem when transporting water — aka what makes water go to the diff parts of the plant and why?
The water in the stomata are evaporating and creating different water potential (low water potential higher up the plant — near the stomata in the leaves)
- Therefore the water absorbed by the roots will travel along the water potential (high -> low) — transpiration pulling them
Why does water form a droplet when on non-polar molecules?
It’s averse to it and thus shrinks to smallest surface area possible -> droplet