Chapter 3 - Water and Life Flashcards
Four of water’s properties that facilitate an environment for life are…
- Cohesive behavior
- Ability to moderate temperature
- Expansion upon freezing
- Versatility as a solvent
Cohesion
The linking together of like molecules, often by hydrogen bonds.
Adhesion
The clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds.
Surface tension
The measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.
How does Water Moderate Temperature?
- Water absorbs heat from warmer air and releases stored heat to cooler air
- Water can absorb or release a large amount of heat with only a slight change in its own temperature
Heat
A measure of the total amount of kinetic energy due to molecular motion
Temperature
Measures the intensity of heat due to the average kinetic energy of molecules.
Calorie (cal)
the amount of heat required to raise the temperature of 1 g of water by 1°C.
Joule (J)
unit of energy where 1 J = 0.239 cal, or 1 cal = 4.184 J
Specific heat
The amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC.
The specific heat of water is…
1 cal/g/ºC Water resists changing its temperature because of its high specific heat. This minimizes temperature fluctuations to within limits that permit life.
Water has a high specific heat because…
– Heat is absorbed when hydrogen bonds break – Heat is released when hydrogen bonds form
Heat of vaporization
The heat a liquid must absorb for 1 g to be converted to gas.
Evaporative cooling
The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state. Evaporative cooling of water helps stabilize temperatures in organisms and bodies of water.
Ice floats in liquid water because…
Hydrogen bonds in ice are more “ordered,” making ice less dense.
Water reaches its greatest density at…
4°C
Solution
A liquid that is a homogeneous mixture of substances.
Solvent
The dissolving agent of a solution.
Solute
The substance that is dissolved.
Aqueous solution
A solution in which water is the solvent.
Water is a versatile solvent due to its…
polarity, which allows it to form hydrogen bonds easily.
Hydration shell
This forms when an ionic compound is dissolved in water. Each ion is surrounded by a sphere of water molecules.
Can water dissolve Water can also compounds made of nonionic polar molecules?
Yes. Even large polar molecules such as proteins can dissolve in water if they have ionic and polar regions.
Hydrophilic Substance
A substance that has an affinity for water.