Osmosis practical

• What are the dependent, independent and control variables in this practical?

  independent - sucrose concentration

  
  

  dependent - mass of potato

  
  

  control - time, starting mass of potatoes, temperature, type of potato
• what is this practical to investigate?

  the effect of sucrose concentration on osmosis in potatoes
• what should you use to cut the potatoes?

  Cork borer
• what should you use to weigh the potatoes?

  mass balance
• why is it important to use a pure water solution

  to have a standard to compare the mass of the potatoes to
• why is drying the potatoes with a towel important

  to ensure excess water is removed for more accurate measurements
• how do you calculate percentage change in mass

  (final mass - initial mass)/ initial mass × 100
• what does a positive and negative percentage change in mass tell you

  positive - gained mass

  negative - lost mass
• Step 1

  Prepare sucrose solutions of various concentrations with a mesuring cylinder add 20cm3 of each solution to a separate boiling tube. Label each tube.
• Step 2

  Cut 6 potato cylinders from the potato into lengths of 50 mm with a knife and ruler blot them dry with a paper towel
• Step 3

  Record the mass of each potato cylinder using a balance write this in the table. Immerse the potato cylinders in each concentration of sucrose solution and cover with a bung.
• Step 4

  After 30 minutes, take out the potato cylinders and dry them. Record the lengths and mass of each cylinder in a table
• Variables

  Independent: concentration of solution

  Dependent: percentage mass change

  Control: surface area, type and age of potato, length