Investigation focus
This lab uses observable phenomena to connect molecular structure to macroscopic properties. You are expected to explain what happens using polarity, partial charges, and hydrogen bonding—not simply describe what you see.
Safe materials only
Suitable materials: water, salt water, sugar water, dish-soap solution, vegetable oil, food colouring, paper towel, coins/pennies, capillary tubes or narrow straws, ice, and room-temperature containers.
Student information
Pre-lab molecular model
1. Why is a water molecule polar?
2. What is a hydrogen bond in water?
3. Predict how disrupting hydrogen bonding might change the behavior of water.
Station 1 — Cohesion & Surface Tension
Coin-drop investigation- Place a clean, dry coin on a flat surface.
- Add water one drop at a time to the center of the coin. Count the drops until the dome collapses.
- Repeat for three trials.
- Repeat the same procedure using dilute dish-soap solution.
| Liquid | Trial 1 | Trial 2 | Trial 3 | Average drops | Observation |
|---|---|---|---|---|---|
| Water | — | ||||
| Dilute soap solution | — |
AP-level analysis: Why did adding soap change the number of drops the coin could hold?
Station 2 — Adhesion & Capillary Action
Paper towel / narrow tube investigation- Place colored water in a beaker or cup.
- Insert one end of a paper towel strip or narrow capillary tube into the water.
- Observe the movement of water upward over time.
- Record the height reached at the specified times.
| Time | Height of water (cm) | Observation |
|---|---|---|
| 1 min | ||
| 3 min | ||
| 5 min |
AP-level analysis: Explain how both cohesion and adhesion contributed to the upward movement of water.
Station 3 — Water as a Polar Solvent
Solubility comparison- Add a small, equal amount of each test substance to separate cups of water.
- Stir each for the same amount of time.
- Record whether the substance dissolves, partially dissolves, or remains separate.
| Substance added to water | Prediction | Result | Molecular explanation |
|---|---|---|---|
| Table salt | |||
| Sugar | |||
| Vegetable oil |
AP-level analysis: Why is the phrase “like dissolves like” useful, but incomplete, when explaining water as a biological solvent?
Station 4 — Ice, Density & Hydrogen Bonding
Solid vs liquid water- Place one ice cube into a clear container of liquid water.
- Observe whether the ice sinks or floats.
- Record what the observation indicates about relative density.
| Observation | Density inference | Hydrogen-bond explanation |
|---|---|---|
Biological significance: Why is it important that ice is less dense than liquid water?
Optional extension — Temperature Stability & Evaporative Cooling
Water has a relatively high specific heat. How does hydrogen bonding help explain this property?
How does evaporation cool a surface?
Synthesis — From Molecular Structure to Biological Function
1. Which observed property depended most clearly on cohesion? Use evidence from your data.
2. How can the same molecular feature—water polarity—help explain both capillary action and solubility?
3. Choose one property investigated and explain why it matters for living organisms.
4. Construct a cause-and-effect chain from oxygen's electronegativity to one emergent property of water.
AP Biology CER Conclusion
Write a Claim–Evidence–Reasoning conclusion explaining how hydrogen bonding gives rise to the observed properties of water.
Completion status
Complete the observations and AP-level explanations. Your work can be saved locally on this device.
Submit to Myers Science Hub
When your lab is complete, submit your responses directly to the MSH backend. Your local saved copy will remain on this device.