Question 1 — Dye movement in celery stalks vs temperature
Compare how far a coloured dye travels up celery stalks standing in ice-cold and warm water baths, then measure an insect photograph and draw a celery leaf.
RUN IT ON THE BENCH
Your readings feed straight into the answer table below as you record them.
ON YOUR BENCH — FROM THE CONFIDENTIAL INSTRUCTIONS
Question 1 — materials
- celery stalks(2)
- 100 cm³ beaker of dye(2)
- 250 cm³ beaker of ice-cold water(1)
- empty 250 cm³ beaker labelled W(1)
Question 1 — apparatus
- white tile(1)
- thermometer(1)
- stop-clock(1)
- knife or scalpel(1)
- hand lens(1)
- permanent marker pen(1)
- 30 cm ruler with a mm scale(1)
- paper towels(5)
- suitable eye protection(1)
- gloves(1 pair)
THE BENCH — TWO CELERY STALKS, ONE ICE-COLD BATH, ONE WARM BATH
Place both stalks first.
Why does warmer water move the dye further?
The dye rides the transpiration stream — water pulled up through the xylem as it evaporates from the cut surface and (in a whole plant) the leaves. Warmth speeds up both evaporation and the kinetic energy of water molecules, so the whole column moves faster. It's the same reason washing dries quicker on a hot day.
Isn't this osmosis?
No solute concentrations are being compared here, and nothing is crossing a partially permeable membrane by diffusion down a water potential gradient cell-to-cell. This is bulk flow of water (carrying dye with it) up hollow xylem vessels — mass transport, not osmosis.
Why does the investigation need repeating?
One stalk in one beaker is one data point. A single unusually fast or slow stalk would look like a real result unless you had other runs to compare it against — repeating lets you spot anomalies and trust the trend rather than a fluke.
YOUR TASKS · 0/4
- ✓Place both stalks and record the starting temperatures
- ✓Run the fixed 3-minute period and record the final temperatures
- ✓Cut sections in beaker C until the dye disappears
- ✓Cut sections in beaker W until the dye disappears
TABLE 1.1 & 1.2 — YOUR READINGS
| BEAKER C | BEAKER W | |
|---|---|---|
| starting temp /°C | — | — |
| final temp /°C | — | — |
| sections cut | — | — |
| distance /mm | — | — |
Copy these into Table 1.1 (temperatures) and Table 1.2 (sections and distance) on the question paper.
YOUR ANSWERS
Record the starting temperatures of the water in large beaker C and large beaker W in Table 1.1, then (later) their final temperatures.
| large beaker C | large beaker W | |
|---|---|---|
| starting temperature of the water /°C | ||
| final temperature of the water /°C |
Prepare a table and record your results. Include the number of 5 mm sections cut before the dye was no longer visible, and the total distance moved by the coloured dye, for both celery stalks.
| beaker C (cold) | beaker W (warm) | |
|---|---|---|
| number of sections cut | ||
| total distance moved by the dye /mm |
Calculate the rate of movement of the dye in the celery stalk in beaker W. Include the unit.
State a conclusion for this investigation.
This investigation was only done once. Explain why it is better to repeat an investigation.
Identify two variables that were kept constant in this investigation.
The data you have recorded in Table 1.1 may indicate that there is a source of error with the method used in this investigation. Identify the possible error and describe an improvement to the method to reduce the effect of this error.
In step 9, it is difficult to determine precisely the final position of the dye in the xylem. Suggest an improvement to the method that would reduce this source of error.
Line AB represents the body length of the black aphid in Fig. 1.5 (magnification ×35). Measure line AB, then calculate the actual body length of the black aphid using magnification = (length of line AB) / (actual body length). Give your answer to one significant figure.
State three ways that the leaf miner fly shown in Fig. 1.6 differs from the black aphid shown in Fig. 1.5.
Fig. 1.7 is a photograph of a celery leaf. Draw a large diagram of the celery leaf shown in Fig. 1.7.
Carbon dioxide moves into celery leaves for photosynthesis. State the name of an indicator which could be used to test for the presence of carbon dioxide gas.