[Part 2]- Required practicals🔬 Flashcards
Describe the required practical, of how to investigate the effects of osmosis in plant tissue. 🥔🍠🍟
1) first peel the potato- since the potato skin, can affect osmosis.
2) use a cork borer to produce three cylinders of a potato- using a cork borer, makes all of the potato cylinders, the same diameter.
3) trip the cylinders to the same length [around 3cm], using a scalpel- if shorter cylinders are used, we might not be able to measure the effects of osmosis.
4) measure the length of each cylinder using a ruler, and the mass of each cylinder using a [mass] balance
5) place each cylinder into a test tube, adding 10cm^3 of a 0.5 molar sugar solution, to the first test tube.
6) then add 10cm^3 of 0.25 sugar solution to the second test tube; adding 10cm^3 of distilled water, to the third test tube- distilled water is used compared to tap water, since it contains no dissolved substances, that could affect the rate of osmosis.
7) leave the potato cylinders overnight, allowing osmosis to take place.
8) remove the potato cylinders, and gently roll them on paper towel, to remove any surface moisture- don’t press on them, other water could be forced out of the cells.
9) once again, measure the length and the mass of the cylinders again.
10) now calculate the percentage change in length and mass
11) plot a graph of mass/length, against the concentration of the sugar solution.
What is the formula for percentage change ?
change in original value
____________________ ✖100
original value
Why does the potato cylinder gain mass ? 🥔🍠🍟
- in water the potato cylinder gains mass, as water moves into it by osmosis.
Why does the potato cylinder lose mass, in a concentrated sugar solution ? 🥔🍠🍟
- in a concentrated sugar solution, the potato cylinder loses mass because water moves out by osmosis.
What can you tell me about the graph of mass/length, against the concentration of the sugar solution ? 🥔🍠🍟
- there is no change in mass, where the lines crosses the x axis. [this is the approximate concentration, inside the cell.]
- This is because the concentration outside the cell, is the same as the concentration inside the cell, therefore no overall osmosis takes place.
When investigating the effects of osmosis in plant tissue, what is the independent variable ? 🥔🍠🍟
- the independent variable, is the concentration of the sugar solution
When investigating the effects of osmosis in plant tissue, what is the dependent variable ?🥔🍠🍟
- the dependent variable, is the mass of the potato cylinders/chip mass.
When investigating the effects of osmosis in plant tissue, what are the control variables ?🥔🍠🍟 [3]
- the control variables are:
- the type and volume of solute in solution
- temperature
- and time.
When investigating the effects of osmosis in plant tissue, what are the sources of inaccuracy/errors ?
- some potato cylinders weren’t fully dried, so the excess water gives a higher mass
- these can both be reduced by repeating the experiment, then calculating a mean percentage change at each concentration
When investigating the effects of osmosis in plant tissue, what are the sources of inaccuracy/errors ?
- water could evaporate from the beakers, meaning the concentration of the sugar solutions would change.
- these can both be reduced by repeating the experiment, then calculating a mean percentage change at each concentration
Describe steps one to two, of the required practical, about how to investigate the effects of osmosis in plant tissue. 🥔🍠🍟
1) first peel the potato- since the potato skin, can affect osmosis.
2) use a cork borer to produce three cylinders of a potato- using a cork borer, makes all of the potato cylinders, the same diameter.
Describe steps three to four, of the required practical, about how to investigate the effects of osmosis in plant tissue. 🥔🍠🍟
3) trip the cylinders to the same length [around 3cm], using a scalpel- if shorter cylinders are used, we might not be able to measure the effects of osmosis.
4) measure the length of each cylinder using a ruler, and the mass of each cylinder using a [mass] balance
Describe steps five to six, of the required practical, about how to investigate the effects of osmosis in plant tissue. 🥔🍠🍟
5) place each cylinder into a test tube, adding 10cm^3 of a 0.5 molar sugar solution, to the first test tube.
6) then add 10cm^3 of 0.25 sugar solution to the second test tube; adding 10cm^3 of distilled water, to the third test tube- distilled water is used compared to tap water, since it contains no dissolved substances, that could affect the rate of osmosis.
Describe steps seven to eight, of the required practical, about how to investigate the effects of osmosis in plant tissue. 🥔🍠🍟
7) leave the potato cylinders overnight, allowing osmosis to take place.
8) remove the potato cylinders, and gently roll them on paper towel, to remove any surface moisture- don’t press on them, other water could be forced out of the cells.
Describe steps nine and ten of the required practical, about how to investigate the effects of osmosis in plant tissue. 🥔🍠🍟
9) once again, measure the length and the mass of the cylinders again, [and now calculate the percentage change in length and mass- 10]
11) plot a graph of mass/length, against the concentration of the sugar solution.
