Osmosis Flashcards

All 6 cards in this deck

What is osmosis?

The net movement of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane.

True or false? A red blood cell placed in pure water will burst.

True. Water moves into the cell by osmosis down a concentration gradient, so the cell swells and bursts (lyses).

What happens to a plant cell placed in a concentrated salt solution?

Water moves out by osmosis through the partially permeable membrane, so the cell loses mass and becomes plasmolysed (shrinks).

What are the steps to investigate osmosis in potato tissue?

e.g. using sucrose solutions of $0.0$, $0.2$ and $0.4$ mol/dm$^3$

1. Cut potato chips of equal size, blot them dry and record the initial mass of each.
2. Place one chip in each sucrose concentration for the same time, keeping temperature and volume of solution the same.
3. Blot dry, reweigh and calculate the percentage change in mass for each concentration.

What are the steps to calculate the percentage change in mass of a potato chip?

e.g. initial mass $5.0$ g, final mass $6.0$ g

1. Change in mass = final − initial: $6.0 - 5.0 = 1.0$ g
2. Divide by the initial mass: $1.0 \div 5.0 = 0.2$
3. Multiply by 100: a $20\%$ gain in mass (a negative answer is a loss).

On a graph of percentage change in mass against sucrose concentration, what does the point where the line crosses the x-axis (0% change) show?

The concentration that is the same as the concentration inside the potato cells, so there is no net movement of water by osmosis.