1. Osmosis in Red Onion Cells (more fun with microscopes)

2. Phase 1: Dry Mount Obtain a thin, purple piece of onion
Place it on a slide, shiny side up
No water!!!
Observe and draw on low power, then find the most purple section, and observe and draw on medium power

3. Phase 2: Saltwater Wet Mount
Add 2-3 drops of saltwater to same onion (use cover slip too)
Observe 2-3 min on low power and draw
Initially you’ll see changes along the perimeter, but as time passes, you’ll see changes throughout the cell
Observe a noticeably affected area under medium power
Draw

4. Prepare Slide for Phase 3
Gently place slide in freshwater to rinse (be careful not to lose the onion!)
Gently dry the slide by dabbing onion tissue dry

5. Phase 3: Distilled Water Wet Mount
Place 2-3 drops of distilled water on same onion slide (use cover slip)
Watch cells for 2-3 minutes on low power and draw
Should start to see changes around the perimeter
Observe a noticeably affected area under medium power and draw

6. Questions
1. When the salt solution was added to the onion cells, where was the greater concentration (most pure) of water (inside or outside the cell membrane)? How do you know?
2. In the winter, grass often dies near the roads that have been covered in salt to remove the ice. Using what you have learned in this experiment, what do you think is the reason the grass dies?

10. 3 minutes after distilled water