gases & liquids plant physiology uni spring 2009
TRANSCRIPT
Gases & Liquids
Plant Physiology UNI
Spring 2009
Properties of gases & liquids
gases liquids
density (L/H)
Properties of gases & liquids
gases liquids
density (L/H) lower higher
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F)
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction between molecules(near 0/lots)
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction between molecules(near 0/lots)
zero for ideal gas
yes, holds molecules together
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction btwn molecules (0/lots)
zero for ideal gas
yes, holds molecules together
Change in V with temp (little/lots)
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction btwn molecules (0/lots)
zero for ideal gas
yes, holds molecules together
Change in V with temp (little/lots)
lots little
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction btwn molecules (0/lots)
zero for ideal gas
yes, holds molecules together
Change in V with temp (little/lots)
lots less
Change in V with P(little/lots)
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction btwn molecules (0/lots)
zero for ideal gas
yes, holds molecules together
Change in V with temp (little/lots)
lots less
Change in V with P(little/lots)
lots almost none
Properties of gases & liquids
gases liquids
density (L/H) lower higher
diffusion (S/F) faster slower
interaction btwn molecules (0/lots)
zero for ideal gas
yes, holds molecules together
Change in V with temp (little/lots)
lots little
Change in V with P(little/lots)
lots almost none
Quiz—State & pressure
Demonstrations
Syringe sealed at bottom
Liquid
Air
Pull up
What is holding up this part of the water drop?
What will happen to the liquid when we pull up?What happens to air & liquid pressures?
Acting out a gas
• Student volunteers
• Gas molecules don’t hold onto each other
• Can compress if contained (can push) – big volume change
• Can't pull (no connection between molecules)
• Gases: can push but not pull
• Gases: under positive pressure only
Acting out a liquid (water)
• Same volunteers• Can push or pull: molecules bound to each other
– Especially true for water– More like solid than like gas
• Positive or negative P (“pressure” or “tension”)– Compression: P is + – Tension: P is - (like solid)
• Must contain liquid to push (like gas)
Gas in liquid—acting out in class
• Same volunteers
• Make the middle molecule a gas– Can push – Can't pull
• Gas bubble is called embolism – may occur naturally
• Embolisms stop transport based on pulling
Archaic use of “tension”
• Hypertension, oxygen tension in blood, high tension electrical wires
• “Tension” was used to mean + pressure – Still use this sense in medicine
• Gas pressure can be lower than atmospheric, but that is still positive – Low pressure is positive– Vacuum is zero pressure – No negative pressures in gases
Water: gas, liquid & solid
• Life mostly water: properties critical
• Boil or evaporate: big change in volume
• Small volume change when we make ice
• Polar molecules– Not stuck together in gas– Stuck together loosely in liquid– Stuck together tightly in solid