LF-01 · TEACHER LESSON PLAN

Osmosis egg lab

Why a shell-less egg swells in water and shrinks in syrup

BiologyGrades 6–93 sessions · 95 min hands-onHazard lowNGSS MS-LS1-2

01 //

Driving question

START THE LESSON WITH THISAn egg with no shell is placed in plain water and another in corn syrup. After one day, one egg is bigger and one is smaller. What moved, and why?

02 //

Learning objectives

Students predict the direction of net water movement across a selectively permeable membrane from a difference in dissolved sugar.
Students calculate mass change and percent change from their own measurements, keeping the sign (+ or −).
Students write a claim supported by their own numbers and a reason that uses the word “net”.

03 //

Standards

Dimension	Alignment
Performance expectation	MS-LS1-2Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function. (Partial alignment: students use the egg membrane as a model of the cell membrane boundary.)
Practices	SEP 3Plan and carry out investigations SEP 4Analyze and interpret data
Core idea	LS1.AThe cell membrane forms the boundary that controls what enters and leaves the cell.
Crosscutting	Cause and effectA concentration difference causes a net movement of water.

Standards text paraphrased from nextgenscience.org. Alignment is partial; a model egg does not cover every part of the performance expectation.

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 MS-LS1-2	Partial model connection: students use the egg membrane to reason about a boundary, but the egg is not a whole-cell model and does not represent the other cell parts in the expectation.	Open standard ↗
Texas	Science.8.11(A)	Partial connection: students discuss membrane transport as a cell-part function, but the egg investigation does not identify the functions of the other listed organelles.	Open standard ↗
Florida	SC.6.L.14.4	Partial connection: the benchmark includes cell membrane structure and function; this lesson models transport across a membrane but does not compare the full set of organelles named in the benchmark.	Open standard ↗
New York	NYSSLS MS-LS1-2	Partial model connection: the membrane model supports discussion of what crosses a cell boundary, but does not address the whole-cell system or all parts required by the expectation.	Open standard ↗
Pennsylvania	STEELS 3.1.6-8.B	Partial model connection: students use egg data to reason about a membrane's role, but do not model the whole cell or the other parts that contribute to its function.	Open standard ↗

04 //

Materials and prep timeline

PER GROUP

2 raw eggs of similar size, plus 1 spare
White vinegar, about 600 mL for the shell step
250 mL distilled water and 250 mL corn syrup
3 clear cups, labels and a marker
Balance reading to 0.1 g, a spoon, paper towels
Splash goggles and disposable gloves

TEACHER ONLY

For 20, 25 or 30 students, stage 5, 7 or 8 complete group kits; print one student sheet per student.
A tray for carrying cups
Bleach-free wipes for benches

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	5	5 complete kits	20 copies	5 groups of 4
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

SESSION 1 · 10 MINStart the shell step

Cover each egg with vinegar and cover the cup. Leave 24 h, then replace the vinegar. 48 h in total.

SESSION 2 · 40 MINPredict, weigh, soak

Rinse and blot gently. Record the start mass. Place the eggs in water and syrup. Soak 24 h at room temperature.

SESSION 3 · 45 MINMeasure and explain

Blot and reweigh. Calculate. Graph. Write the claim, evidence and reasoning.

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.

A shell-less egg model illustrates water movement across a semipermeable membrane in lower- and higher-solute environments. — **Explain the membrane model.**Use the diagram to discuss water movement; the egg is a model, not a cell.

Vinegar dissolves the calcium-carbonate shell while the soft egg membrane remains for gentle transfer. — **Prepare without damaging the membrane.**Rinse gently after shell removal, inspect for fragments, and handle the shell-less egg with care.

A blank before-and-after mass record compares shell-less eggs soaked in distilled water and corn syrup. — **Record each starting and ending mass.**The graphic shows a typical possible pattern; students record their actual measurements.

04B //

Printable shopping list

TEACHER PREP · Osmosis egg 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

2 raw eggs of similar size, plus 1 spare
White vinegar, about 600 mL for the shell step
250 mL distilled water and 250 mL corn syrup
3 clear cups, labels and a marker
Balance reading to 0.1 g, a spoon, paper towels
Splash goggles and disposable gloves

TEACHER-PROVIDED MATERIALS + SETUP RULES

For 20, 25 or 30 students, stage 5, 7 or 8 complete group kits; print one student sheet per student.
A tray for carrying cups
Bleach-free wipes for benches

QUANTITIES BY CLASS SIZE

Material	Per group kit	20 students	25 students	30 students
Raw eggs, including one spare per group	3	15	21	24
White vinegar for shell step	about 600 mL	3 L	4.2 L	4.8 L
Distilled water	250 mL	1.25 L	1.75 L	2 L
Corn syrup	250 mL	1.25 L	1.75 L	2 L
Clear cups, labels and marker	3 cups, 1 set	15 cups, 5 sets	21 cups, 7 sets	24 cups, 8 sets
Balance reading to 0.1 g	1	5	7	8
Spoon, towels, goggles and gloves	1 kit	5 kits	7 kits	8 kits
Student sheets	1 per student	20	25	30

Prepare 5 kits for 20 · 7 kits for 25 · 8 kits for 30 students.

05 //

Lesson flow

Minutes	What happens
S2 · 0–5	Engage Show the driving question. Students vote “bigger / smaller / same” for each cup on the student sheet and write one reason.
S2 · 5–30	Explore Groups rinse and blot the eggs, record the start mass to 0.1 g, label cups, pour the liquids and lower the eggs with a spoon. Circulate and check that both eggs get the same blot routine.
S2 · 30–40	Clean up and wash hands. Cups go on the tray. Pause point: ask “what would make this unfair?” and collect two ideas.
S3 · 0–10	Explore Lift, blot with the same routine, reweigh on the same balance. Record. Note texture (firm, floppy, wrinkled).
S3 · 10–25	Explain Calculate change in grams and percent change, keeping the sign. Draw the bar graph. Use the discussion questions below.
S3 · 25–35	Elaborate “Move the syrup egg into water. Predict what happens and why.” Open the interactive lab for the 24-hour recovery model.
S3 · 35–45	Evaluate Students write the claim, evidence and reasoning. Use the rubric below.

06 //

Discussion questions

1. In which cup did the measured mass suggest net water moved out of the egg? How do you know?

SAMPLE ANSWERIf the syrup egg lost mass, that result is consistent with net water moving out. Compare the recorded change with the water egg, and note that one egg per liquid is a classroom demonstration rather than enough replication to establish a reliable average.

2. Water molecules move both ways. Why did the egg still change mass?

SAMPLE ANSWERMore water moved one way than the other. That difference is the net movement, and it set the direction of the mass change.

3. Why is the vinegar shell step not one of the two treatments?

SAMPLE ANSWEREvery egg goes through it for the same time. It prepares the membrane; it is not the thing being compared.

4. How is the egg a good model of a cell, and where does it fall short?

SAMPLE ANSWERIt shows a membrane controlling what crosses. A real cell also has transport proteins and other parts, so the egg does not show every way a cell moves materials.

07 //

Common misconceptions

STUDENTS OFTEN SAY“Water only goes one way.”

BETTER IDEAWater crosses both ways; the concentration difference makes one direction larger. Say “net movement”.

STUDENTS OFTEN SAY“The egg soaks it up like a sponge.”

BETTER IDEAThe egg is not absorbing by capillary action. The membrane lets water cross; most of the sugar stays outside.

STUDENTS OFTEN SAY“Syrup got inside the egg.”

BETTER IDEAThe large sugar molecules cross the membrane far less readily than water, so the mass change is mainly water.

08 //

Differentiation

SUPPORT

Pre-labelled data table with the formula printed above it
Sentence starters for the claim: “The egg in ___ gained/lost ___ g because water moved ___.”
Calculator allowed; teacher models the first row

EXTEND

Add salt water or two sugar concentrations and predict the order of percent change
Repeat with 3 eggs per liquid and compare the spread
Explain how a pickle, a slug and a salted road each show a related idea

09 //

Assessment rubric

Criterion	Beginning	Developing	Secure
Claim	No claim, or only “it changed”.	States which egg gained or lost mass.	States the direction of net water movement for both liquids.
Evidence	No numbers from the table.	Uses one number or leaves out the sign.	Uses start, final and % change with correct signs and units.
Reasoning	Says “osmosis” without a reason.	Mentions sugar or water but not the difference.	Links the concentration difference to net water movement across the membrane.
Data care	Different routines for each egg.	Same routine, units missing.	Same blot, same balance, units in every cell.

10 //

Vocabulary

Osmosis – Net movement of water across a selectively permeable membrane.
Selectively permeable – Lets some substances cross more easily than others.
Concentration – How much dissolved substance is in a volume of liquid.

Net movement – The difference between movement in and movement out.
Percent change – Change ÷ start × 100.
Control – A condition kept the same so the comparison is fair.

11 //

Safety, cleanup and troubleshooting

BEFORE STUDENTS TOUCH ANYTHING

Raw eggs can carry Salmonella: gloves on, never taste, wash hands and wipe the bench.
Vinegar irritates eyes: splash goggles while pouring.
Used eggs and liquids go in the trash, not down a shared sink, and are never food.

Troubleshooting: Little change: check for shell patches and whether the liquid covered the egg. Torn membrane: record it as a damaged sample and swap in the spare.