PSS EXAM 2 LATEST 2025 WITH CORRECT
QUESTIONS AND DETAILED ANSWERS/ALREADY
GRADED A+
*Intro to Soil Water* - CORRECT ANSWER-...
Where is Earth's water? - CORRECT ANSWER--Oceans (97%)
-Atmosphere (<1%)
-Ice (2%)
-Saline lakes (<1%)
-Fresh lakes & rivers (<1%)
-Soil moisture (<1%)
-Ground water (<6%)
Why study soil water? - CORRECT ANSWER--plant survival and growth
-loss of chemicals by leaching
-groundwater contamination
-evapotranspiration
,-nutrient availability
-soil workability, consistence
-soil aeration
Soil water: - CORRECT ANSWER--water behaves differently than water in a river
or glass
-associated with soil particles, which affects its movement; water can flow up in
the soil!
Properties of water that greatly influence nature of soil water: - CORRECT
ANSWER--polarity
-hydrogen bonding
-cohesion/adhesion
-surface tension
Polarity of water - CORRECT ANSWER--causes attractions b/w water & other
things with charges (including water molecules!)
-Negative end (oxygen) attracted to cations (+ charged ions)
-Positive end (hydrogens) attracted to clay particles (- charged ions)
Hydrogen bonds - CORRECT ANSWER-weak bonds b/w the H of one water
molecule and the O of another
-H-bonds join a chain of water molecules
,Cohesion - CORRECT ANSWER-causes water molecules to stick to each other
Adhesion (adsorption) - CORRECT ANSWER-causes water molecules to stick to
other materials (like soil particles)
Surface tension - CORRECT ANSWER-water molecules are more attracted to
each other than to the air around them--gives the water the appearance of having
an elastic membrane covering the surface
Capillary rise is due to... - CORRECT ANSWER--adhesion to the surface and
cohesion to itself
-the height of rise is inversely proportionate to the pore/capillary radius: h=0.15/r
(finer the soil texture, the higher the capillary rise)
-In a sand, capillary rise will be fast but not high
-In a clay, capillary rise will be slow but higher than sand
-In a loam, capillary rise will be somewhere in the middle
*Capillary "rise" can take place horizontally AND vertical in a a soil
Potential energy - CORRECT ANSWER--key to understand movement of water
through soil (movement in soils is too slow for kinetic energy to have large
influence)
, -high energy status -> low energy status
-we can use this to predict movement of water through the soil
3 forces act on soil water & affect its energy: - CORRECT ANSWER--Matric
-Osmotic
-Gravity
Matric forces - CORRECT ANSWER--attraction of water to soil solids (same
principle that causes capillary rise in pores)
-energy of water is lower nearer to particle surfaces -- molecules have less
freedom of movement so lower energy
Osmotic forces - CORRECT ANSWER--water is attracted to ions & solutes, which
reduces the energy state of water
-Dilute solution (high energy) -> Concentrated solution (low energy)
-Excess salts: can happen in arid environments; house plants can suffer from
excess salts
-Salts in water draw water our of root tissue, killing plants
Gravity - CORRECT ANSWER--pulls water downward
QUESTIONS AND DETAILED ANSWERS/ALREADY
GRADED A+
*Intro to Soil Water* - CORRECT ANSWER-...
Where is Earth's water? - CORRECT ANSWER--Oceans (97%)
-Atmosphere (<1%)
-Ice (2%)
-Saline lakes (<1%)
-Fresh lakes & rivers (<1%)
-Soil moisture (<1%)
-Ground water (<6%)
Why study soil water? - CORRECT ANSWER--plant survival and growth
-loss of chemicals by leaching
-groundwater contamination
-evapotranspiration
,-nutrient availability
-soil workability, consistence
-soil aeration
Soil water: - CORRECT ANSWER--water behaves differently than water in a river
or glass
-associated with soil particles, which affects its movement; water can flow up in
the soil!
Properties of water that greatly influence nature of soil water: - CORRECT
ANSWER--polarity
-hydrogen bonding
-cohesion/adhesion
-surface tension
Polarity of water - CORRECT ANSWER--causes attractions b/w water & other
things with charges (including water molecules!)
-Negative end (oxygen) attracted to cations (+ charged ions)
-Positive end (hydrogens) attracted to clay particles (- charged ions)
Hydrogen bonds - CORRECT ANSWER-weak bonds b/w the H of one water
molecule and the O of another
-H-bonds join a chain of water molecules
,Cohesion - CORRECT ANSWER-causes water molecules to stick to each other
Adhesion (adsorption) - CORRECT ANSWER-causes water molecules to stick to
other materials (like soil particles)
Surface tension - CORRECT ANSWER-water molecules are more attracted to
each other than to the air around them--gives the water the appearance of having
an elastic membrane covering the surface
Capillary rise is due to... - CORRECT ANSWER--adhesion to the surface and
cohesion to itself
-the height of rise is inversely proportionate to the pore/capillary radius: h=0.15/r
(finer the soil texture, the higher the capillary rise)
-In a sand, capillary rise will be fast but not high
-In a clay, capillary rise will be slow but higher than sand
-In a loam, capillary rise will be somewhere in the middle
*Capillary "rise" can take place horizontally AND vertical in a a soil
Potential energy - CORRECT ANSWER--key to understand movement of water
through soil (movement in soils is too slow for kinetic energy to have large
influence)
, -high energy status -> low energy status
-we can use this to predict movement of water through the soil
3 forces act on soil water & affect its energy: - CORRECT ANSWER--Matric
-Osmotic
-Gravity
Matric forces - CORRECT ANSWER--attraction of water to soil solids (same
principle that causes capillary rise in pores)
-energy of water is lower nearer to particle surfaces -- molecules have less
freedom of movement so lower energy
Osmotic forces - CORRECT ANSWER--water is attracted to ions & solutes, which
reduces the energy state of water
-Dilute solution (high energy) -> Concentrated solution (low energy)
-Excess salts: can happen in arid environments; house plants can suffer from
excess salts
-Salts in water draw water our of root tissue, killing plants
Gravity - CORRECT ANSWER--pulls water downward
