Paper 1 practicals Flashcards
how to investigate osmosis in potato strips in terms of the percentage change in mass of potato a different solutions?
with a waterproof pen label each tube with the name of one of the solutions. A potato carefully with a paper towel. Measure its mass on the balance. The potato strip into one of the tubes record the label on the tube and the mass of the strip. Repeat until all strips have been placed in tubes. Carefully fill each tube with the appropriate solution so that the potato is fully covered. leave the tubes overnight to allow osmosis to happen. then use the forceps to remove each potato strip from its tube, blot dry on a paper towel and measure its mass again.
Iodine test for starch?
place one spatula of powdered food on a dish. using a dropper place a few drops of ID solution onto the food record the letter of the food and any change in the colour of solution. if it has started it will change to a black blue colour.
Benedict’s test for reducing sugars?
place two spatulas of powdered food into a test tube. add 1 cm³ of water to the tube and stir to mix. Add an equal volume of Benedict solution and mix. place the tube in a water bath at about 95° for a few minutes record the letter of the food and the colour of the solution. It should give a green-yellow-red solution
Biuret test for protein?
Grind up the food sample and put it into a beaker and add some distilled water. Stir well with a glass rod to allow some food to dissolve. Filter the mixture through a funnel with filter paper. Add 2cm3 of the filtered solution into a clean test tube. Add 2cm3 of Biuret solution and gently shake the tube. If food has protein, will turn purple
Emulsion test for lipids?
place two spatulas of powdered food into a test tube. Add 2 cm³ of Sudan 3 to the tube place a bung in the end of the tube and shake the tube vigourously. Allow contents to settle. Pour the liquid from the top of the mixture into a test tube half filled with water. If lipids are present, the water will be cloudy
investigate the effect of light intensity on the rate of photosynthesis
Start by taking a boiling tube and placing it 10 cm away from an LED light source. (LED is used as it doesn’t release much heat which could affect the experiment). fill the boiling tube with sodium hydrogen carbonate solution, which releases CO2. Put a piece of pondweed into the boiling tube. leave for five minutes. We should see bubbles of gas being produced from the end of the pondweed (oxygen). start a stopwatch and count the number of bubbles we see in one minute repeat twice and calculate the mean number of bubbles per min. repeat the whole experiment again from 20cm then 30cm then 40cm.
Alternative way to count bubbles in photosynthesis experiment? (volume of oxygen)
place a funnel over the pondweed and catch the bubbles in a measuring cylinder then use the measuring cylinder to measure the volume of oxygen gas produced
3 control variables in investigating enzymes?
Volume of amalyse and starch
Concentration of amalyse and starch
the pH
investigating effect of pH on enzyme activity?
1) put starch and amalyse into boiling tubes then in water bath at 30°
2) Mix starch amalyse and iodine solution
3) Pipette mixture to spotting tile every 10 seconds
4) Record time from colour changes from blue/black to orange
5) repeat with different temps and record time
6) keep volume pH and concentration constant
Microscopes
How to prepare a microscope slide?
1) place a drop of water on the slide
2) use tweezers to add the specimen on top of water drop
3) Put a cover slip and ensure no bubbles
4) add a dye
magnification?
image size/actual size
