practicals

• what is the microscopy practical method?

  1. rotate the objective lens so the lower power is in line with the stage
  2. turn the coarse focus until the stage is as close to the objective lens as possible
  3. place prepared slide onto stage
  4. focus slide using fine focus adjustment
  5. draw an image of what you see
• what risks are there for the microscopy practical?

  1. light from microscope could be too bright
  2. care must be taken with the slides as they can break easily and cut you
• what is the independent variable?

  the variable that is changed
• what is the dependent variable?

  the variable that is measured
• what is the control variable?

  the variable that is kept the same
• what are the variables in the microscopy experiment?

  independent = the magnification

  dependent = the microscope used

  control = the type of cell - onion or cheek
• how could the microscopy experiment be improved?

  using an electron microscope to improve image quality of the cell
• what is the method for the osmosis practical?

  1. set up six boiling tubes containing different concentrations of the sugar solution
  2. prepare 6 potato cylinders, dry them and record each of their mass
  3. place one potato into each boiling tube and leave for 40 minutes
  4. remove each potato, pat dry and record mass
• what are the risks for the osmosis practical?

  1. cut your hand whilst chopping potato
  2. wear eye protection whilst using sucrose solution
• what are the variables in the osmosis practical?

  independent = the concentration of the sucrose solution

  dependent = the change in mass of the potato

  control = the time the potatoes are left in the solution
• what is the test for sugars and what is the method?

  benedict's test

  add benedict's solution to food in boiling tube

  place tube with food and solution in water bath

  positive = any colour except blue
• what is the test for starch and what is the method?

  iodine

  add iodine to food

  positive = will turn blue/black
• what is the test for proteins and what is the method?

  biuret

  add biuret solution to food solution and mix

  positive = purple/purple ring between the layers
• what is the test for fats and what is the method?

  Sudan III

  add water to food being tested then a few drops of sudan III

  positive =red layer on the top
• what is the method for photosynthesis practical?

  1. place sodium hydrogencarbonate into boiling tube
  2. cut a piece of pondweed and place into boiling tube
  3. position boiling tube 10cm away from light source and let it stand for five minutes
  4. during this time count bubbles emerging from the pondweed
• what are the variables in the photosynthesis experiment?

  independent = distance from light source

  dependent = number of bubbles produced

  control = concentration of hydrogencarbonate solution