# RP: Osmosis Practical Flashcards

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1
Q

What is the independent variable?

A

The independent variable is the one you change.

2
Q

What is the dependent variable?

A

The dependent variable is the one you measure.

3
Q

What is the control variable?

A

The control variable is the one you keep the same.

4
Q

What is the osmosis practical?

A

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.

5
Q

What is the independent variable in the osmosis practical?

A

Independent variable:
Concentration of salt solutions

6
Q

What is the dependent variable in the osmosis practical?

A

Dependent variable:
Mass/ length of potato.

7
Q

What is the control variable in the osmosis practical?

A

Control variable:
Time vegetable is soaked in salt solution.

8
Q

What piece of equipment is used to make the potato cylinder in the osmosis practical?

A

A cork borer is used to make the potato cylinder.

9
Q

What piece of equipment is used to cut off the potato skin in the osmosis practical?

A

A scalpel is used to cut of the potato skin

10
Q

What three posibilties will occur once the potato has soaked in the salt solution?

A
• Gains mass
• Loses mass
• Mass is the same
11
Q

When does the potato gain mass?

A
• If it is in a dilute solution, it will gain mass.
• The solution is hypotonic to the solution inside the cell.
12
Q

When does the potato lose mass?

A
• If it is in a concentrated solution, it will lose mass.
• The solution is hypertonic to the solution in the cell.
13
Q

When does the potato mass stay the same?

A
• If it is in the same concentration as the potato salt solution.
• The solution is isotonic to the solution in the cell .
14
Q

What does “dilute” mean?

A

A substance that contains more solvent than dissolved solute.

15
Q

What does “concentrated” mean?

A

A substance that contains more dissolved solute than solvent.

16
Q

Give 2 factors that depend on whether a substance will diffuse through a semi- permeable membrane.

A
• Solubility of substance
• Size of molecules
17
Q

What is a turgid cell?

A

One that is swollen/ hard due to the gain of water.

18
Q

What is lysis?

A

Lysis is when an animal cell splits down a cell membrane.

19
Q

When does lysis occur to an animal cell?

A

Lysis occurs when an animal cell is placed in a hypotonic solution.

20
Q

What is the process of “crenation?”
TIP: THINK OF CREMATED BODIES

A

Crenation is the shrivelling of a cell when it is placed in a hypertonic solution.

21
Q

What are the 8 steps of the osmosis practical?

A

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

22
Q

Why is it good to cover the testube in this prcactical?

A
• Evaporation changes concentration of salt solutions.
• Cover to reduce evaporation
23
Q

What are 2 ways to improve the osmosis practical?

A
• Repeat experiment: mean percentage change.
• Lid on beaker
24
Q

What are 2 pieces health and safety do you need to know for this practical?

A
• Be careful when using sharp knives
• Keep water away from electronic balance.
25
Q

Why is percentage change better than just knowing change?(2)

A
• They all start at different masses
• Percentages show how much water is absorbed/ lost relative to the initial mass.
26
Q

Why do we peel the skin off the potato before cutting the potatos?

A
• Skin may affect rate of osmosis.
27
Q

Why is it important to use potato cylinders of the same length when seeing how concentration of salt solution affects osmosis? (1 mark)

A

Potato cylinders need to have the same surface area as that affects rate of osmosis.