PSS Exam #2 Questions and Correct Answers 2025/2026

PSS Exam #2 Questions and Correct Answers 2025/2026 *Intro to Soil Water* - Answer -... Where is Earth's water? - Answer --Oceans (97%) -Atmosphere (<1%) -Ice (2%) -Saline lakes (<1%) -Fresh lakes & rivers (<1%) -Soil moisture (<1%) -Ground water (<6%) Why study soil water? - Answer --plant survival and growth -loss of chemicals by leaching -groundwater contamination -evapotranspiration -nutrient availability -soil workability, consistence -soil aerationSoil water: - 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: - Answer --polarity -hydrogen bonding -cohesion/adhesion -surface tension Polarity of water - 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 - 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 - Answer -causes water molecules to stick to each other Adhesion (adsorption) - Answer -causes water molecules to stick to other materials (like soil particles) Surface tension - 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 surfaceCapillary rise is due to... - 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