Chapter 2

Question 1

Why is water a universal solvent?

Answer 1

Because water can dissolve more substances than any other liquid

• a solvent is able to dissolve other substances

Question 2

Solid water (ice) is ___ dense than liquid water

Answer 2

Less!

• this is why ice floats

Question 3

What is polarity in water?

Answer 3

• water is composed of two hydrogen atoms and one oxygen atom, which forms polar covalent bonds.
• the polarity of water creates a slightly positive charge for hydrogen and a slightly negative charge for oxygen, which causes water molecules to attract.

Question 4

What does polarity mean?

Answer 4

That it is a good solvent, aka “universal solvent”

• water cannot dissolve non-polar substances such as oils and fats

Question 5

What is electronegativity?

Answer 5

A chemical property that describes the tendency of an atom to attract electrons.

Question 6

Why does water have high electronegativity?

Answer 6

The electronegativity of oxygen is much higher than that of hydrogen

• this makes water polar.

Question 7

How are water molecules connected?

Answer 7

Through hydrogen bonds

• this leads to low boiling and melting points
• also creates surface tension, and explains why water droplets are attracted to each other.

Question 8

What are some properties of humidity and condensation?

Answer 8

• warm water can hold more water vapor
• Condensation occurs when relative humidity is at 100%

Question 9

What is dew point temperature?

Answer 9

the temperature at which current absolute humidity equals 100% relative humidity

Question 10

Where does humidity and condensation occur?

Answer 10

In mist and clouds

Question 11

What are the three mechanisms for precipitation?

Answer 11

1. Convective
2. Frontal (extratropical cyclones/lows)
3. Orographic (mountain)

• they all involve adiabatic cooling
• chinook / foehnwinds = adiabatic heating

Question 12

What is adiabatic heating/cooling?

Answer 12

Changes in temperature by the expanding (cooling) or compression (warming) of a body of air as it rises or descends on the atmosphere, with no exchange of heat with the surrounding air

Question 13

What is evaporation?

Answer 13

The conversion of liquid water into water vapor returning to the atmosphere

• evaporation happens through open water and soils

Question 14

What is evapotranspiration?

Answer 14

evaporation + transpiration

• when water is transferred from the land to the atmosphere by evaporation from the soil and and transpiration from plants.

Question 15

What is PET and AET?

Answer 15

Potential Evapotranspiration (in a perfect world)

• evapotranspiration if there is water available, not limiting

Actual Evapotranspiration

• almost always equal or less than PET

Question 16

What is a lysimeter?

Answer 16

A device that measures AET for a vegetated surface based on weight

• underground metal cylinders with grass and soil inside

Question 17

What is climate moisture index (CMI) and how do you calculate it?

Answer 17

The difference between annual precipitation and potential evapotranspiration

CMI = P - PET

• when CMI is less than 0, precipitation is greater than potential evapotranspiration

Question 18

What is runoff and how do you calculate it?

Answer 18

• The amount of water that moves into streams and further downstream, divided by watershed area.

Runoff (mm) = Volume (m3) / watershed area (m2) * 1000

Question 19

What is the water balance equation?

Answer 19

change in storage = precipitation - evapotranspiration - runoff

• sometimes its necessary to account for groundwater flows
• other times it can be assumed that change in storage and groundwater flow equals zero.