Dilution series (P3)

• What is the aim of this practical

  To find the water potential of plant tissue using a dilution series of sucrose solution
• what measurements are taken before and after the experiment

  mass of plant tissue (eg potato cylinders) before and after incubation in solutions
• what is % change in mass used instead of just mass change

  to allow comparison between samples of different initial sizes
• how is water potential determined from a graph

  the sucrose concentration where % change in mass is zero indicates the water potential of the tissue
• what is the dependent variable in this practical

  the % change in mass of the plant tissue
• What is the purpose of a dilution series in practical biology?

  To create different concentrations of a solution
• What are the required practicals linked to dilution series?

  • Required Practical 3: Investigating water potential of plant tissues
  • Required Practical 11: Creating glucose concentration solutions using a calorimeter
• What is a dilution series?

  Step-by-step dilutions to create different concentrations
• How do you create a tenfold dilution from a stock solution of 100?

  Mix one part stock with nine parts water
• What is the concentration after the first dilution from a stock solution of 100?


  10 concentration
• What is the concentration after diluting tenfold again from 10 concentration?

  1 percent concentration
• Why is using a dilution series advantageous?

  It improves accuracy without measuring small volumes
• What is the first step to make a one in ten dilution?

  Add one part bacteria culture to nine parts water
• What must be done after mixing the dilution?

  Mix thoroughly for even distribution
• How do you create a one in a thousand dilution from the one in ten dilution?

  Mix one part of ten with nine parts water
• What are the two key formulas for dilution series?

  1. $c_1 \times v_1 =$$c_2 \times v_2$

  • $c_1$: initial concentration
  • $v_1$: volume of stock solution
  • $c_2$: final concentration
  • $v_2$: final volume

  1. $v_2 =$$v_1 +$$v_{water}$

  • $v_{water}$: volume of water added
• What is the first step in solving a dilution series math question?

  Highlight all numerical values given
• What does $c_2$ represent in the dilution formula?


  The concentration of the solution being made
• How do you find $v_1$ using the dilution formula?


  Rearrange $c_1 \times v_1 =$$c_2 \times v_2$
• What is the unit for volume in dilution calculations?

  Centimeters cubed
• What is the missing heading in a dilution table for a sucrose solution?

  Volume of distilled water
• How do you calculate the volume of distilled water needed?

  Use $v_2 - v_1$
• What is the final volume of the solution if $v_1$ is 1.6 cm³ and $v_{water}$ is 18.4 cm³?


  20 cm³
• What are common challenges students face with dilution series questions?

  • Misunderstanding the formulas
  • Missing numerical values in tables
  • Confusing units of measurement