RP: Osmosis Practical Flashcards
What is the independent variable?
The independent variable is the one you change.
What is the dependent variable?
The dependent variable is the one you measure.
What is the control variable?
The control variable is the one you keep the same.
What is the osmosis practical?
Osmosis practical:
What is the concentration of the salt in a potato?
Put the potato into different concentrations of salt solution until there is no change.
What is the independent variable in the osmosis practical?
Independent variable:
Concentration of salt solutions
What is the dependent variable in the osmosis practical?
Dependent variable:
Mass/ length of potato.
What is the control variable in the osmosis practical?
Control variable:
Time vegetable is soaked in salt solution.
What piece of equipment is used to make the potato cylinder in the osmosis practical?
A cork borer is used to make the potato cylinder.
What piece of equipment is used to cut off the potato skin in the osmosis practical?
A scalpel is used to cut of the potato skin
What three posibilties will occur once the potato has soaked in the salt solution?
- Gains mass
- Loses mass
- Mass is the same
When does the potato gain mass?
- If it is in a dilute solution, it will gain mass.
- The solution is hypotonic to the solution inside the cell.
When does the potato lose mass?
- If it is in a concentrated solution, it will lose mass.
- The solution is hypertonic to the solution in the cell.
When does the potato mass stay the same?
- If it is in the same concentration as the potato salt solution.
- The solution is isotonic to the solution in the cell .
What does “dilute” mean?
A substance that contains more solvent than dissolved solute.
What does “concentrated” mean?
A substance that contains more dissolved solute than solvent.
Give 2 factors that depend on whether a substance will diffuse through a semi- permeable membrane.
- Solubility of substance
- Size of molecules
What is a turgid cell?
One that is swollen/ hard due to the gain of water.
What is lysis?
Lysis is when an animal cell splits down a cell membrane.
When does lysis occur to an animal cell?
Lysis occurs when an animal cell is placed in a hypotonic solution.
What is the process of “crenation?”
TIP: THINK OF CREMATED BODIES
Crenation is the shrivelling of a cell when it is placed in a hypertonic solution.
What are the 8 steps of the osmosis practical?
1.) Cut off skin using scalpel
2.) Cork borer–> 5 cyclinders
3.) Use scalpel –> make lengths equal (3cm)
4.) Measure the mass of each cylinder
5.) 10cm³ of each concentration in boiling tubes + distilled water
LEAVE
6.) Blot cyclinders with paper towel
7.) Measure mass and length again: calculate percentage change.
8.) Plot results on a graph
Why is it good to cover the testube in this prcactical?
- Evaporation changes concentration of salt solutions.
- Cover to reduce evaporation
What are 2 ways to improve the osmosis practical?
- Repeat experiment: mean percentage change.
- Lid on beaker
What are 2 pieces health and safety do you need to know for this practical?
- Be careful when using sharp knives
- Keep water away from electronic balance.
Why is percentage change better than just knowing change?(2)
- They all start at different masses
- Percentages show how much water is absorbed/ lost relative to the initial mass.
Why do we peel the skin off the potato before cutting the potatos?
- Skin may affect rate of osmosis.
Why is it important to use potato cylinders of the same length when seeing how concentration of salt solution affects osmosis? (1 mark)
Potato cylinders need to have the same surface area as that affects rate of osmosis.
