Blog

IB CHEMISTRY: INTERNAL ASSESSMENT & EXTENDED ESSAY II
  • focuschemistry
  • July 23, 2020
  • IB IA and EE

Independent and Dependent Variables – What to consider

In every IA or EE, the decision on which variable to manipulate and which variable that the manipulated variable affects is important.  Typically, it is advisable to have only ONE dependent variable for IA and at least TWO for EE.   The key reason for this difference is the amount of time that one spends in the laboratory – 10 hours for IA and 40 hours for EE.  The big difference in the amount of time spent in the laboratory means two things

  • The independent and dependent variables for IA should be easily measurable.
  • The independent and dependent variables for EE can more complicated and indirect in measurement, but the method of measurement must be verified.

Independent Variable

There are principally two types of independent variables

  • Type of reagent such as type of acid/base, catalyst/inhibitor etc
  • Reaction condition such as temperature, pH, concentration, light intensity, light wavelength etc.

There are students who used other types of independent variables, such as

  • Brands of household product, beverage, food etc
  • Types of food and beverage

Some examples are

  • Brands of detergents
  • Types of tea, eg.English breakfast tea, Ceylon tea etc.
  • Types of coffee eg. Arabica coffee, Blue Mountain coffee etc

While exploring the difference in types of food and beverage or brands of products may seem like a possible independent variable, we highly discourage it.  The reason is that it will be very challenging to explain the results of the experiment using concepts in Chemistry, thus the “discussion” section of the report will not be substantial.

Some independent variables are harder to control, such as the wavelength or intensity of light.  Such independent variables manipulation requires the setup of special units that disallow ambient light interference.  We have helped students design and built such setups for experiments, and are contactable through email or phone for a discussion.

Dependent variable

In deciding the dependent variable, one has to consider the following

  • Is the independent measurable using existing equipment or using methods doable in the school laboratory?

For example,

– Temperature using thermometer

– Concentration of coloured liquid substances using UV-VIS spectrophotometer or colorimeter

– Concentration of certain colourless organic liquid substances using uv-vis spectrometer

  • Some students might vary the type of chemicals used in the experimental study. In this case, the student should check if the chemical(s) is available in the laboratory or permissible (non-hazardous or carcinogenic) in the laboratory.   In some cases, the chemical might not be available in the school laboratory and the cost of the chemical might be beyond the budget allocated to each student.  In such a scenario, it might be possible that the student has to pay for the chemical required.

Feel free to contact us via email or phone for a more detailed discussion of how we can support you in your IA or EE project.