Summary Co-Ordinated Sciences 0654 Alternative to Practical
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Course
Science
Institution
GCSE
A summary for iGCSE Co-Ordinated Sciences 0654 Alternative to Practical including all of the experiments required and all of the biological or chemical tests. Also includes ensuring accuracy and other theory aspects. I achieved an A* in my mock.
Drawings
● The drawing should be as large as the space provided.
● It has definite outlines (no 'sketchy’ lines)
● No shading.
● No arrow heads when labelling
● Lines point exactly at the labelled part.
Graphs
● Label both axes including the units
● Choose an even scale for each axis that uses up as much of the grid as possible.
● The independent variable is plotted on the x-axis
● The dependent variable (i.e. the one that changes due to a change of the other) is plotted
on the y-axis.
● Join your plotted points with ruled lines
● When drawing bar charts, all bars must be of the same width
● The bars, when drawn cannot touch each other
Designing An Experiment
● Find the variable which is to be changed (from the question) and mention how you are
going to change it
● List all variables that you have to keep constant throughout the experiment
● Mention how long your experiment will last.
● Say how you will measure experiments‘ results (change in colour for example)
● Write: 'repeat experiment to get more reliable results and minimise error’
● Set a control for your experiment
Biological Tests
╳ Test Additional Step + Result - Result
Starch Add drops of iodine ╳ Blue/back Orange/brown
Reducing Add Benedict’s reagent Heat in a water bath Orange/red Blue
sugars
Proteins Add Bieuret’s reagent Shake Mauve/purple Blue
Fats Add ethanol Pour into a test tube Milky-white No change
with water emulsion
Investigating The Need For Chlorophyll
Leaves can´t be tested for glucose because it’s quickly used, so we test for starch (glucose stored
in chloroplasts where photosynthesis occurs).
1. Boil a leaf for 30s to break down the cell membranes.
2. Place the leaf into an ethanol-filled tube in the boiling water 5-10 mins, removing the
chlorophyll so we can see the colour change from the test.
3. Put it back into the boiling water to soften it.
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, 4. Cover with iodine in a white tile.
5. A green leaf will turn blue wherever photosynthesis is occuring in the leaf.
Turn off the bunsen burner when using ethanol as it’s extremely flammable.
This method can test whether chlorophyll is needed or not by using a variegated leaf. - the
areas without chlorophyll will remain brown as photosynthesis isn´t occuring there since there is
no starch.
Investigating The Need For Light
Don´t detach the leaf from the plant.
1. Leave the plant in a cupboard for 24 h to destarch it.
2. Check the leaves don't have starch.
3. Partially cover the leaf and leave it under the sun for 24h.
4. Remove the paper and test the leaf for starch, the covered part will turn brown and the
not covered blue-black. This shows starch is only produced where light hits, meaning
light is needed.
Investigating The Need For CO2
1. Destarch two plants.
2. Place one plant in a bell jar which contains a beaker of sodium hydroxide (which will
absorb carbon dioxide from the surrounding air).
3. Place the other plant in a bell jar which contains a beaker of water (control experiment),
which will not absorb carbon dioxide from the surrounding air.
4. Place both plants in light for hours then test them for starch.
5. The leaf near the NaOH will remain brown and the other one will turn blue.
Investigating Transpiration
● Use a sharp razor blade to cut a leafy shoot underwater.
● Insert the leafy shoot through the hole of the stopper provided with the potometer.
● Fill the potometer with water and fit the stopper holding the leafy shoot to the apparatus.
● Trap an air bubble in the capillary tube by the following procedures:
○ dip the end of the capillary tube into a beaker of water,
○ close the tap of the reservoir,
○ take away beaker of water and allow the plant to transpire
○ re-immerse the capillary tube into the beaker of water again.
● Estimate rate of transpiration by measuring distance moved by the air bubble per unit
time
Investigating Differences in Inspired and Expired Air
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