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