Predict which way water will move

Science · Organisms & Life Processes · ages 17-18

Name ______________________ Date ____________

Why does pure water sit at zero?
- Scientists voted zero as the nicest number
- Zero is the reference with nothing dissolved and no pressure
- Water has no mass at all
What two main pieces add up to water potential?
- Solute potential and pressure potential
- Colour and temperature
- Size and weight of the container
A plant has pressure potential 0.21 and solute potential minus 3.50. Type its total water potential.
Answer: ______________
After months of drought the soil drops below the plant. What happens now?
- Flow continues into the plant as before
- Flow reverses, leaving the plant toward the soil
- Water potential stops existing
Soil sits near zero after rain; the plant totals minus 3.29. Which way does water move?
- It stays perfectly still
- From plant into the soil
- From soil into the plant
In the U-tube, pressure pushed water right. How does adding solute left bring levels back?
- It drags the left total back down until sides match
- It removes the membrane
- It raises the right side higher
Why do leaf stomata tend to close during drought?
- To cut evaporation loss and hold remaining potential
- To let more water escape faster
- To photosynthesise in the dark
A student says bigger solute particles pull harder per particle. What is wrong?
- Solute never affects water at all
- Nothing; size is what matters
- Count matters, not size of particles

Answer key

For grown-ups. Fold this page away before handing over the rest.

Zero is the reference with nothing dissolved and no pressure · Everything else is measured against that reference point.
Solute potential and pressure potential · Dissolved stuff lowers it, pressure raises or lowers it.
-3.29 · Add the two pieces: 0.21 plus minus 3.50.
Flow reverses, leaving the plant toward the soil · The rule never changes; only the numbers flipped.
From soil into the plant · Water moves from higher potential to lower potential.
It drags the left total back down until sides match · Solute lowers; pressure raises; the total decides.
To cut evaporation loss and hold remaining potential · Closing the tiny pores keeps what little water the plant holds.
Count matters, not size of particles · More dissolved particles means lower potential, whatever their size.