LF-22 · TEACHER LESSON PLAN

Celery and food coloring lab

Why colored water climbs a celery stalk into its leaves

BiologyGrades 3–715 min setup; 24–48 h observationHazard low; food coloring stains and adult knife preparationNGSS 4-LS1-1

01 //

Driving question

START THE LESSON WITH THISColored water climbs celery stalks and appears as lines in their leaves. How are different starting water temperatures associated with the arrival time and visible path?

02 //

Learning objectives

Students prepare three repeated cups for each cold, room-temperature and comfortably warm starting-water condition.
Students record starting water temperature and its drift at 2, 4 and 24 hours, leaf-arrival times, and visible color height after 24 hours.
Students explain how colored water traces vascular tissue and why a cut stalk is a limited model of water transport in a whole plant.

03 //

Standards

Dimension	Alignment
Performance expectation	4-LS1-1Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction. (Limited connection: students observe colored water in celery vascular tissue, but this cut-stalk model does not test how plant structures support the whole plant's survival or growth.)
Practices	SEP 4Analyze and interpret data. SEP 6Construct explanations and design solutions.
Core idea	LS1.APlants and animals have both internal and external structures that serve various functions in growth, survival, behavior, and reproduction.
Crosscutting	Structure and functionThe way an organism's structures work together can support its functions.

Standard text paraphrased from the Next Generation Science Standards. This is a limited connection because a colored-water celery stalk is a model of vascular transport, not evidence for every part of whole-plant survival and growth.

03A //

State standards crosswalk

Use the row as a planning crosswalk, then confirm local district pacing and grade placement. “Partial” labels describe a skill connection, not full mastery of the complete standard.

State	Verified standard	How this lesson aligns	Official source
California	CA NGSS 4-LS1-1	Limited connection: the colored pathway makes an internal plant structure visible, but the activity does not argue how structures support all listed life functions.	Open standard ↗
Texas	Science.4.13(A)	Partial connection: students observe a plant structure and relate it to water transport, but do not investigate the full range of plant structures and functions.	Open standard ↗
Florida	SC.3.L.14.1	Partial connection: the celery stalk supports discussion of plant structure and function, but this activity focuses on one transport pathway rather than comparing plant and animal structures.	Open standard ↗
New York	NYSSLS 4-LS1-1	Limited connection: students use an internal plant structure as evidence, but the cut-stalk model does not address the complete survival, growth, behavior, and reproduction expectation.	Open standard ↗
Pennsylvania	STEELS 3.1.4.A	Partial connection: students connect a plant structure with water movement, while the lesson does not examine the wider set of structures and functions in the standard.	Open standard ↗

04 //

Materials and prep timeline

PER GROUP

Nine similar fresh celery stalks with leafy tops
Nine same-size cups with 100 mL water in each
10 drops of food coloring per cup, 90 drops total
Cold, room-temperature and comfortably warm starting water; thermometer
Rulers, labels, timers, covered work surface and recording sheet

TEACHER ONLY

Immediately before setup, an adult makes a fresh angled cut (about 45°) across each base with a sharp knife on a stable cutting board; do not use scissors, which can crush the stem.
Prepare nine cups with 100 mL water and 10 drops of identical food coloring each. Use comfortably warm starting water, not hot, and similar leafy stalks.
Cover the bench and place labeled cups on a stable surface. Record temperatures at setup and at 2, 4 and 24 hours; cups on the bench are not temperature-controlled. Provide cleanup supplies; dyed celery is not food.

CLASS-SIZE KIT PLANNER

One per-group kit contains every item in the team materials list above. Groups are balanced around the listed 3–4 students target.

Students	Groups	Per-group kits	Student sheets	Suggested group split
20	6	6 complete kits	20 copies	2 groups of 4 and 4 groups of 3
25	7	7 complete kits	25 copies	4 groups of 4 and 3 groups of 3
30	8	8 complete kits	30 copies	6 groups of 4 and 2 groups of 3

DAY 1 SETUP — 0–5 MINPredict and label

Predict which cup may show color in its leaves first. Label the temperatures and review dye-stain and no-eating reminders.

DAY 1 SETUP — 5–15 MINStart nine stalks

Prepare three 100 mL cups with 10 food-coloring drops for each starting temperature. An adult cuts about 1 cm from each base at about 45° with a sharp knife on a stable board; do not use scissors. Place one fresh-cut stalk per cup, record actual starting temperatures and start together.

DAY 1 — AT 2 H AND 4 HCheck temperatures and leaves

Record each starting group's measured water temperature and check for first leaf color at consistent times. Log each cup separately; do not call the starting temperature a maintained 24-hour treatment.

DAY 2 — AT 24 HMeasure color height

Record the 24-hour temperature and measure the highest visible color path in every stalk in centimeters. Record thin vascular streaks as observed; do not infer unseen flow.

BY 48 HSummarize repeats and clean

If leaf color has not appeared, continue observations to 48 hours and record no arrival by then. Calculate arrival-time mean/range only for groups where all three cups show color; otherwise report the non-arrival count and observed times. Calculate height mean/range from all three 24-hour readings, then clean the covered area and wash hands.

04A //

Lab figures and data visuals

Reviewed article images support the lesson flow. Use the tables and student sheet to record actual observations; pictured patterns are not target results.

Nine similar fresh celery stalks stand in identical cups of the same red dye water, in three groups of three for cold, room-temperature, and warm starting conditions. — **Repeat each starting-temperature condition three times.**Use the same red dye, cup size, water volume, and similar stalks across all nine cups. The comparison is by starting temperature.

A cut celery cross-section highlights xylem pathways carrying colored water toward leaves and transpiration from leaf surfaces. — **The dye traces water-conducting tissue.**Xylem moves water through the stalk, while cohesion, adhesion and leaf transpiration help explain upward transport in the cut-stalk model.

Three groups of three celery cups with an observation timeline and repeated blank recording tables for cold, room-temperature, and warm starting water. — **Log temperature changes and every stalk's result.**Record actual group temperatures at setup, 2, 4, and 24 hours, plus each cup's leaf-arrival time and visible path height at 24 hours.

04B //

Printable shopping list

TEACHER PREP · Celery and food coloring lab

Shopping and staging checklist

Multiply the per-group kit contents by the class-size planner. The teacher section includes teacher-provided materials and setup or safety notes.

PER-GROUP KITS

Nine similar fresh celery stalks with leafy tops
Nine same-size cups with 100 mL water in each
10 drops of food coloring per cup, 90 drops total
Cold, room-temperature and comfortably warm starting water; thermometer
Rulers, labels, timers, covered work surface and recording sheet

TEACHER-PROVIDED MATERIALS + SETUP RULES

Immediately before setup, an adult makes a fresh angled cut (about 45°) across each base with a sharp knife on a stable cutting board; do not use scissors, which can crush the stem.
Prepare nine cups with 100 mL water and 10 drops of identical food coloring each. Use comfortably warm starting water, not hot, and similar leafy stalks.
Cover the bench and place labeled cups on a stable surface. Record temperatures at setup and at 2, 4 and 24 hours; cups on the bench are not temperature-controlled. Provide cleanup supplies; dyed celery is not food.

QUANTITIES BY CLASS SIZE

Material	Per group kit	20 students	25 students	30 students
Fresh leafy celery stalks	9	54	63	72
Clear cups	9	54	63	72
Water at 100 mL per cup	900 mL	5.4 L	6.3 L	7.2 L
Food coloring at 10 drops per cup	90 drops	540 drops	630 drops	720 drops
Rulers, thermometers, timers and labels	1 of each	6 of each	7 of each	8 of each
Student recording sheets	1 per student	20	25	30
Covered work surface and cleanup supplies	1 shared station	1	1	1

Prepare 6 kits for 20 · 7 kits for 25 · 8 kits for 30 students.

05 //

Lesson flow

Minutes	What happens
Day 1 setup — 0–5 min	Engage Predict which cup may show color in its leaves first. Label the temperatures and review dye-stain and no-eating reminders.
Day 1 setup — 5–15 min	Explore Prepare three 100 mL cups with 10 food-coloring drops for each starting temperature. An adult cuts about 1 cm from each base at about 45° with a sharp knife on a stable board; do not use scissors. Place one fresh-cut stalk per cup, record actual starting temperatures and start together.
Day 1 — at 2 h and 4 h	Explore Record starting-group temperature and check for first leaf color at consistent times. Log each cup separately and identify the treatment as starting temperature only.
Day 2 — at 24 h	Explain Record the 24-hour temperature and measure the highest visible color path in every stalk in centimeters. Record thin vascular streaks as observed; do not infer unseen flow.
By 48 h	Evaluate If leaf color has not appeared, continue observations to 48 hours and record no arrival by then. Calculate arrival-time mean/range only if all three cups show color; otherwise report the non-arrival count and observed times. Summarize all three 24-hour heights, compare the temperature log, then clean the covered area and wash hands.

06 //

Discussion questions

1. Why does the color often appear as narrow lines in the celery?

SAMPLE ANSWERThe dye traces water moving through vascular bundles, including xylem pathways, rather than evenly coloring every part of the stalk.

2. Why start the three stalks at the same time with equal water and dye?

SAMPLE ANSWERThat makes the planned difference—water temperature—a clearer comparison. Unequal volumes or start times could change the color path independently.

3. Does a higher visible color line measure all water moving through the stalk?

SAMPLE ANSWERNo. It shows the highest visible dye path at the observation time, not total water flow; dye visibility and stalk structure affect what can be seen.

4. What limits the conclusion from a cut celery stalk?

SAMPLE ANSWERA cut stalk lacks roots and is not a whole growing plant. Stalk size, leaf area, fresh cuts and room conditions vary, so repeat with matched stalks before generalizing.

07 //

Common misconceptions

STUDENTS OFTEN SAY“The dye spreads evenly through the whole stalk.”

BETTER IDEAThe visible lines trace particular vascular bundles; much of the stalk may remain uncolored.

STUDENTS OFTEN SAY“The cut celery has roots that pull water up.”

BETTER IDEAThis cut-stalk demonstration has no roots. The colored path shows movement through vascular tissue, but it is not a complete model of a living plant.

STUDENTS OFTEN SAY“The tallest dye line tells us the total water absorbed.”

BETTER IDEAIt records visible travel height only; it does not directly measure total water flow or uptake.

08 //

Differentiation

SUPPORT

Pre-label cups and provide a check-time card with space for actual elapsed hours.
Place a centimeter ruler beside each stalk and mark the 24-hour reading point on the data sheet.
Offer: ‘At __ h, color reached __ cm in the __ water; color first appeared in leaves after __ h.’

EXTEND

Photograph each stalk at fixed times against the same ruler, background and lighting.
Repeat with similar stalks and compare the range of arrival times, noting leaf area and cut freshness.
Inspect a cross-section with adult help and sketch where colored vascular bundles are visible.

09 //

Assessment rubric

Criterion	Beginning	Developing	Secure
Matched setup	Uses unmatched water or stalks without labeling temperatures.	Labels temperatures but leaves one important condition unmatched.	Uses similar fresh-cut leafy stalks, equal water and dye amounts, and labeled temperature conditions.
Time and height records	Leaves arrival or height blank.	Records observations but omits hours, centimeters or 24-hour endpoint.	Records elapsed hours to leaf color and visible height in cm at 24 h, including no arrival when applicable.
Interpretation	Claims the stalk was colored throughout without evidence.	Uses a visible path but treats it as total water flow.	Uses the observed path and height to describe vascular transport and states what the dye does not measure.
Safe handling	Handles knife or eats dyed celery.	Keeps food away but needs reminders about fresh adult cuts or stains.	Leaves cutting to an adult, works over a cover, does not eat samples and washes hands after cleanup.

10 //

Vocabulary

Vascular tissue – Plant tissue that transports water and other materials through a plant.
Xylem – Vascular tissue that carries water through a plant.
Stalk – The celery stem that supports leaves and contains vascular bundles.

Transport – Movement of material from one place to another.
Elapsed time – Time passed since the stalk was placed in colored water.
Evidence – An observation or measurement used to support an explanation.

11 //

Safety, cleanup and troubleshooting

BEFORE STUDENTS TOUCH ANYTHING

Immediately before setup, an adult cuts about 1 cm from each stalk base at about 45° with a sharp knife; scissors can crush the stem.
Use a stable cutting board and point the knife away from hands. Students place the prepared celery into cups.
Food coloring stains and the dyed celery is not food. Keep samples away from mouths, cover the bench, and wash hands after cleanup.

Troubleshooting: If color does not reach leaves, record the elapsed observation time and continue only through the planned 48-hour window. Check whether the stalk remains in the colored water and note a loose or wilted stalk; do not claim an unobserved arrival. An adult should inspect any cross-section.