Ch 3 - Water Flashcards
(25 cards)
Water is polar. Why is this?
Water is composed of covalent bonds where the oxygen atom gets the electrons more regularly than the hydrogen atoms; thus, oxygen takes on a more negative charge while the hydrogen atoms take on a more positive charge
How much of a living organisms is comprised of water
60%-90%
Hydrogen bonds
Contributes to important properties if water
4 of water’s properties that facilitate life
1: Cohesive behavior
2: Ability to moderate temperature
3: Expansion upon freezing
4: Versatility as a solvent
Cohesion
Attraction between the same substance
Example of cohesion
The hydrogen bonds which hold water molecules together
Adhesion
The attraction between different substances
Example of adhesion
The attraction between water and plant cell walls
What aids cohesion in plants?
Water conducting cels which utilize both the cohesive nature of water and the property if adhesion.
Surface tension
A measure of how hard it is to break the surface of a liquid
Temperature moderation of water
Water absorbs heat from warmer air and releases stored heat to cooler air. Can also absorb/release a large amount of gear with only a slight change in its own temperature.
Specific heat
The amount of heat that must be absorbed or lost for 1g if that substance to change its temperature by 1C.
What is the specific heat if water?
1 cal/(g•C)
How is heat released/absorbed by water?
Heat is released when hydrogen bonds form. Heat is absorbed when hydrogen bonds break.
Heat of vaporization
The heat a liquid must absorb for 1g of of that substance to be converted to gas (water has a high heat if vaporization).
Evaporative cooling
As a liquid evaporates, it’s remaining surface cools.
At what temperature is water’s density highest?
4C –> water becomes less dense as it becomes a solid at lower temperatures
Why is water called the universal solvent?
It can form hydrogen kinds with many other compounds and most biochemical reactions occur in water.
Dissociation
The breaking apart of water molecules into ions in an aqueous solution;
Ions
Molecules with a net positive or negative charge
pH scale
A measure of the acidity or baseness of a solution; the correct balance or H+ and OH- is critical for the proper chemical functioning of organisms.
What happens when an ionic compound is dissolved in water?
Each ion is surrounded by a sphere of water molecules. Even large polar molecules such as proteins can be dissolved in water f they have ionic and polar regions
What area of our solar system contains the proper temperature range suitable for life and the presence of water?
The band where earth and mars exist
What is the focus if astrobiologists seeking life on other planets?
The presence of water.
