Walking water experiment
01 // Question
Which selected paper-towel product moves water farthest along a matched bridge in 60 minutes?
Change the tested product, measure wet-front distance along the towel at 15, 30, and 60 minutes, and use three independent bridges per product. First cup arrival is a separate supporting observation.
02 // Variables
Independent
Type of paper towel- Selected thin, low-cost product
- Selected thick/select-a-size product
- Selected recycled-fiber product; record brand, product, and ply
Dependent
Wet-front distance along the towel at 60 minutes- Distance in centimeters at 15, 30, and 60 minutes on each of three bridges
- First scheduled check when a colored drop is visible in the receiving cup
03 // Hypothesis
IF one selected paper-towel product has fiber spaces that wick water more effectively than the others, THEN its three-bridge mean wet-front distance may be greater after 60 minutes, BECAUSE capillary movement depends on the product's fiber structure and the matched bridge setup; thickness alone does not identify a winner.
04 // Procedure
1. Label nine matched pairs
Use 18 identical plastic or glass cups: three source-and-receiver pairs for each of three selected towel products. Add 150 mL and 3 dye drops to every source cup.
2. Prepare matched bridges
Cut three equal-length and equal-width strips from each product, keep each product's supplied ply structure, record its label/ply, and fold all strips the same way.
3. Start and check consistently
Record a start time as each bridge first touches its source water. Measure along the towel at 15, 30, and 60 minutes; check cup arrival again at 2, 4, and 6 hours, noting the first check with a visible drop and the preceding dry check.
4. Measure the wet front
Mark the source-waterline point on each towel, then use a ruler to measure from that mark to the leading wet edge along the same path. Record centimeters, not cup water level; log first cup arrival separately.
5. Compare three trials
Keep all three readings per product, compare mean wet-front distance and spread at 60 minutes, and report first-arrival checks as observed intervals rather than exact times.
Materials // Prepare the bench
- 18 matching plastic or glass cups
- 1.35 L room-temperature water
- 27 drops of food coloring
- three selected paper-towel products
- ruler
- measuring cup
- timer
- labels
- level tray
05 // Data table
| Product · trial | 15 min front (cm) | 30 min front (cm) | 60 min front (cm) | Arrival interval (last dry to first wet, min) |
|---|---|---|---|---|
| Thin · 1 | ____ | ____ | ____ | ____ |
| Thin · 2 | ____ | ____ | ____ | ____ |
| Thin · 3 | ____ | ____ | ____ | ____ |
| Thick · 1 | ____ | ____ | ____ | ____ |
| Thick · 2 | ____ | ____ | ____ | ____ |
| Thick · 3 | ____ | ____ | ____ | ____ |
| Recycled · 1 | ____ | ____ | ____ | ____ |
| Recycled · 2 | ____ | ____ | ____ | ____ |
| Recycled · 3 | ____ | ____ | ____ | ____ |
06 // What to expect
Water wets cellulose fibers and moves through connected narrow spaces by capillary action; gravity helps it descend after the bridge's high point. A paper towel is a limited model: water transport in living plants also involves xylem structure and transpiration, not capillary rise alone.
When two differently dyed streams enter one cup, the visible color shows that the liquids mixed. It does not mean capillary action created a new substance or that the activity measured diffusion by itself.
07 // Lab notes
- Set all nine pairs on a level, covered tray away from edges and walkways; leave them undisturbed for scheduled checks at 15, 30, and 60 minutes, then 2, 4, and 6 hours.
- Use plastic or glass cups, not paper, so the cups themselves don't absorb water and change the results.
- Food coloring can stain hands and countertops. Do not drink the test water; wipe spills promptly and wash hands after cleanup.
08 // Remember
Water can wick through tiny spaces between paper fibers. Compare three measured bridges per product; thickness alone does not name a winner.
09 // Set up a capillary-action comparison
Choose one specific thin/low-cost product, one thick or select-a-size product, and one recycled-fiber product. Write each package's brand, product name and ply on the record sheet; these labels describe only the products tested, not every towel in that category. Prepare three separate source-and-empty cup pairs per product (nine pairs total). Use the same clear cup size/material, 150 mL of room-temperature water and three dye drops in each source cup.
Cut three strips from each product to the same measured length and width. Fold each strip the same way, preserve the product's supplied ply construction, and record that construction rather than adding or removing layers. Keep cup gaps, starting water levels, strip immersion depth, tray level and check schedule the same. The independent variable is the selected product; the primary outcome is wet-front distance along the towel at 60 minutes.
10 // Explain how water moves through the towel
Water wets cellulose fibers and moves through connected narrow spaces by capillary action; adhesion, cohesion and surface tension all contribute. After water crosses the high fold, gravity helps it descend. The wet front is the leading edge in the towel; it is not the same as water collected in a receiving cup. A paper bridge is a limited model of plant transport: xylem structure and transpiration also matter in living plants.
If differently dyed source cups feed one receiving cup, the resulting color shows that the liquids mixed. It does not mean the towel created a new substance or that this setup isolated diffusion. If a bridge is dry, check both contact points and record the problem before restarting with fresh matched strips.
11 // Make the investigation more informative
Use a level, covered tray away from table edges and electrical devices; food coloring stains, so do not drink the test water and wipe spills promptly. Leave all nine pairs undisturbed between checks. Record front distance along the same towel path at 15, 30 and 60 minutes; check cup arrival again at 2, 4 and 6 hours, recording the last dry check and first check with a visible drop.
Keep the three raw measurements for every product. Compare each product's mean and range for wet-front distance at 60 minutes. The first detected cup-arrival check is only bounded by the last check with no drop and the first check with a drop; report that interval rather than an invented exact arrival time. Do not average these arrival-check windows as if they were precise timestamps. Conclude only about the named products and setup.
12 // Tell capillary rise from water collecting in the cups
A wet mark on the bridge, a wet front at a measured distance, and a visible drop in the receiver are three distinct observations. This lesson measures the advancing front along the towel at 15, 30 and 60 minutes, then checks cup arrival at 2, 4 and 6 hours. Mark where source water meets the towel and measure from that point along the bridge to the wet edge. Start each elapsed-time record when that bridge first contacts its source water; do not call the cup's water level the towel's wet-front distance.
Use three separately assembled bridges for each selected product. Cut all strips to the same length and width, use the same fold and cup gap, and record the product name and supplied ply structure. If the receiver is still dry at a check, retain the distance measurement and continue; at six hours record 'not reached by 6 h.' Compare the mean/range of the three distances at a fixed check, and describe cup arrival only as the interval between the last dry check and first observed drop.
13 // Questions people ask
Why does water travel up a paper towel?
Water wets cellulose and moves through narrow connected spaces among its fibers. Adhesion, cohesion, and surface tension contribute to capillary action; gravity helps water descend after it crosses the fold. Plants use additional structures and transpiration, so a towel is only a limited model.
Will a thick paper towel always move water fastest?
No. Thickness or a product's absorbency claim does not predict a universal winner. Fiber arrangement, ply, strip preparation, cup gap, starting level, and contact affect a particular test; compare the measured products under matched conditions.
Is the time to the first cup drop exact?
Only if someone watches continuously. With scheduled checks, record the first check when a visible drop appears and the preceding check when it was still absent; report that interval instead of inventing an exact arrival time.
What should I record if no water reaches the cup?
Record the wet-front distance at each check and write 'not reached by 6 h' if no drop is visible at the endpoint. Check that both towel ends still touch water and note any setup disturbance.
What do the mixed colors show?
They show that differently dyed water reached the same cup and mixed. The color change does not mean a new substance formed and does not isolate diffusion from the water's movement.
14 // Keep going
Can you explain the investigation?
Walking water experiment · Student Data Sheet
Question: Which selected paper-towel product moves water farthest along a matched bridge in 60 minutes?
Hypothesis: If one selected paper-towel product has fiber spaces that wick water more effectively than the others, then its three-bridge mean wet-front distance may be greater after 60 minutes, because capillary movement depends on the product's fiber structure and the matched bridge setup; thickness alone does not identify a winner.
Materials
- 18 matching plastic or glass cups
- 1.35 L room-temperature water
- 27 drops of food coloring
- three selected paper-towel products
- ruler
- measuring cup
- timer
- labels
- level tray
Safety before starting
- Set cups on a level tray away from table edges. Food coloring can stain skin and surfaces; cover the work area and wipe spills promptly.
- Use clean, room-temperature water only. Do not drink the colored water, and wash hands after setup and cleanup.
Lab notes
- Set all nine pairs on a level, covered tray away from edges and walkways; leave them undisturbed for scheduled checks at 15, 30, and 60 minutes, then 2, 4, and 6 hours.
- Use plastic or glass cups, not paper, so the cups themselves don't absorb water and change the results.
- Food coloring can stain hands and countertops. Do not drink the test water; wipe spills promptly and wash hands after cleanup.
Variables
Independent: Type of paper towel · Dependent: Wet-front distance along the towel at 60 minutes
Keep constant: same cup material and size · 150 mL source water and 3 dye drops per pair · starting water temperature · measured strip length and width · same fold and cup gap · level tray and check schedule
Procedure
- Label nine matched pairs: Use 18 identical plastic or glass cups: three source-and-receiver pairs for each of three selected towel products. Add 150 mL and 3 dye drops to every source cup.
- Prepare matched bridges: Cut three equal-length and equal-width strips from each product, keep each product's supplied ply structure, record its label/ply, and fold all strips the same way.
- Start and check consistently: Record a start time as each bridge first touches its source water. Measure along the towel at 15, 30, and 60 minutes; check cup arrival again at 2, 4, and 6 hours, noting the first check with a visible drop and the preceding dry check.
- Measure the wet front: Mark the source-waterline point on each towel, then use a ruler to measure from that mark to the leading wet edge along the same path. Record centimeters, not cup water level; log first cup arrival separately.
- Compare three trials: Keep all three readings per product, compare mean wet-front distance and spread at 60 minutes, and report first-arrival checks as observed intervals rather than exact times.
Record your observations
| Product · trial | 15 min front (cm) | 30 min front (cm) | 60 min front (cm) | Arrival interval (last dry to first wet, min) |
|---|---|---|---|---|
Answer key and expected pattern
Water wets cellulose fibers and moves through connected narrow spaces by capillary action; gravity helps it descend after the bridge's high point. A paper towel is a limited model: water transport in living plants also involves xylem structure and transpiration, not capillary rise alone.
When two differently dyed streams enter one cup, the visible color shows that the liquids mixed. It does not mean capillary action created a new substance or that the activity measured diffusion by itself.
Remember: Water can wick through tiny spaces between paper fibers. Compare three measured bridges per product; thickness alone does not name a winner.