Osmosis egg lab
01 // Question
How does the liquid an egg soaks in change its mass after 24 hours?
A testable question names one thing you change and one thing you measure.
02 // Variables
Independent
Liquid the egg soaks in- Distilled water
- Corn syrup
Dependent
Change in egg mass- Grams, to 0.1 g
- Percent change
03 // Hypothesis
IF a shell-less egg soaks in corn syrup for 24 hours, THEN its mass will decrease, BECAUSE water moves out through the membrane toward the side with more dissolved sugar.
04 // Procedure
1. Remove the shell
Cover each egg with vinegar for 24 to 48 hours until the shell is gone.
2. Weigh
Rinse, blot dry and record the starting mass to 0.1 g.
3. Soak
Put each egg in 250 mL of its liquid for 24 hours at room temperature.
4. Blot and reweigh
Lift out with a spoon, blot gently and weigh on the same scale.
5. Calculate
Find the change in grams and the percent change for each egg.
Materials // Prepare the bench
- Raw eggs
- white vinegar
- distilled water
- corn syrup
- clear cups
- balance
- spoon
- paper towels
- goggles
- disposable gloves
05 // Data table
| Liquid | Start (g) | After 24 h (g) | Change (g) | % change |
|---|---|---|---|---|
| Distilled water | ____ | ____ | ____ | ____ |
| Corn syrup | ____ | ____ | ____ | ____ |
Formula % change = (mass after − start mass) ÷ start mass × 100
06 // What to expect
In a typical classroom result, the egg in distilled water gains mass and the egg in corn syrup loses mass. Treat these as predictions to compare with your own measurements: the vinegar step only removes the shell, and shell condition, blotting, timing, and membrane damage can affect the result.
Water crosses the egg membrane in both directions. A difference in water concentration can make net movement go toward the side with more dissolved solute, while most large sugar molecules remain outside. The egg is a useful model, not a complete cell membrane model.
07 // Lab notes
- Blot each egg before weighing. Syrup left on the membrane adds mass you did not measure.
- Use the same scale for every weighing and record to 0.1 g.
- The syrup egg turns floppy. Lift it with a spoon so the membrane does not tear.
08 // Remember
Water moves. Sugar mostly stays put. The scale tells you which way the water went.
09 // Prepare a fair osmosis comparison
Set up the shell-removal step one or two days before the measuring session; the long soak is part of the schedule, not a step students can rush during one class period. Label each cup before adding liquid, and use eggs that are as similar in starting size as possible. Record a starting mass only after gently blotting each egg. A thin film of vinegar or syrup can change the balance reading, so use the same blotting routine at the start and finish.
Use enough liquid to cover each egg and keep the cups in the same room-temperature location. The independent variable is the surrounding liquid; the response is mass change. The shell-removal vinegar is a preparation step and should not be confused with the comparison treatment unless the investigation explicitly includes it. A written label with the egg ID, liquid, and start time prevents a common mix-up when the samples have softened overnight.
10 // Turn mass readings into evidence
For each egg, subtract starting mass from final mass. A positive answer means the egg gained mass; a negative answer means it lost mass. To compare eggs of different starting sizes, calculate percent change as change divided by starting mass, multiplied by 100. Keep the sign in the result. Saying only that an egg changed by 4 grams hides whether water moved in or out, which is the central evidence for this question.
The membrane allows water to pass more readily than large dissolved sugar molecules. In distilled water, the solution outside is less concentrated in dissolved material than the egg interior, so net water movement is into the egg. Corn syrup creates the opposite concentration difference, so net water movement is outward. Students should describe net movement, not claim that water molecules travel in only one direction; molecules move both ways while the concentration difference creates a net change.
11 // Troubleshoot and extend the investigation
If a reading changes very little, first check the shell-removal step: a patch of hard shell can block contact with the membrane. Next check whether the egg was weighed wet, whether the soak lasted the same time, and whether the liquid actually covered it. A torn membrane is a damaged sample and should be recorded rather than quietly treated as a normal result. Repeat with fresh eggs if the class needs a reliable comparison.
A useful extension is to test salt water or several sugar concentrations while keeping the egg preparation, liquid volume, temperature, and soak time fixed. Make a prediction about which treatment should produce the largest percent mass change, then compare the prediction with repeated eggs. Do not use this model to claim that every cell behaves exactly like an egg; it demonstrates selective water movement and provides a large, visible membrane model, while real cell membranes have additional structures and transport processes.
12 // Understand what the shell-removal step changes
Vinegar reacts with calcium carbonate in the shell and releases carbon dioxide bubbles while the shell gradually dissolves. The membrane remains as a flexible barrier around the egg contents. Rinse gently after the soak and inspect for hard shell fragments; do not squeeze the egg because the membrane can tear and invalidate the mass comparison.
The shell-removal stage prepares the model but is not the treatment being tested. Keep all eggs in vinegar for a similar period and record any damaged sample before the water or syrup phase. Handle raw eggs with gloves, wash hands and surfaces, and discard samples as directed rather than treating them as food.
13 // Questions people ask
Why does the egg in corn syrup lose mass?
Corn syrup has much more dissolved sugar than the inside of the egg, so water moves out of the egg through its membrane toward the higher sugar concentration, a process called osmosis.
How long does it take to remove an egg shell with vinegar?
Usually 24 to 48 hours. Leave the egg in vinegar until the shell is gone, then rinse it gently as the teacher directs. This is a preparation step shared by both test eggs, not one of the measured treatments.
What is the independent variable in the osmosis egg lab?
The liquid the egg soaks in (typically distilled water versus corn syrup) is the independent variable. The dependent variable is the change in the egg's mass.
14 // Keep going
Can you explain the investigation?
Osmosis egg lab · Student Data Sheet
Question: How does the liquid an egg soaks in change its mass after 24 hours?
Hypothesis: If a shell-less egg soaks in corn syrup for 24 hours, then its mass will decrease, because water moves out through the membrane toward the side with more dissolved sugar.
Materials
- Raw eggs
- white vinegar
- distilled water
- corn syrup
- clear cups
- balance
- spoon
- paper towels
- goggles
- disposable gloves
Safety before starting
- Raw eggs can carry Salmonella. Wear disposable gloves, keep the egg and liquid away from food, never taste the samples, and wash hands and the work surface after cleanup.
- Vinegar can irritate eyes. Wear splash goggles while pouring; if it splashes into eyes or onto skin, rinse with clean water and tell the supervising adult.
Lab notes
- Blot each egg before weighing. Syrup left on the membrane adds mass you did not measure.
- Use the same scale for every weighing and record to 0.1 g.
- The syrup egg turns floppy. Lift it with a spoon so the membrane does not tear.
Variables
Independent: Liquid the egg soaks in · Dependent: Change in egg mass
Keep constant: starting egg size · 250 mL of liquid · room temperature · 24-hour soak · same kind of container
Procedure
- Remove the shell: Cover each egg with vinegar for 24 to 48 hours until the shell is gone.
- Weigh: Rinse, blot dry and record the starting mass to 0.1 g.
- Soak: Put each egg in 250 mL of its liquid for 24 hours at room temperature.
- Blot and reweigh: Lift out with a spoon, blot gently and weigh on the same scale.
- Calculate: Find the change in grams and the percent change for each egg.
Record your observations
| Liquid | Start (g) | After 24 h (g) | Change (g) | % change |
|---|---|---|---|---|
Formula: % change = (mass after − start mass) ÷ start mass × 100
Answer key and expected pattern
In a typical classroom result, the egg in distilled water gains mass and the egg in corn syrup loses mass. Treat these as predictions to compare with your own measurements: the vinegar step only removes the shell, and shell condition, blotting, timing, and membrane damage can affect the result.
Water crosses the egg membrane in both directions. A difference in water concentration can make net movement go toward the side with more dissolved solute, while most large sugar molecules remain outside. The egg is a useful model, not a complete cell membrane model.
Remember: Water moves. Sugar mostly stays put. The scale tells you which way the water went.