You have written a hypothesis, listed your variables and filled a page with numbered instructions. What could still be missing?
A reader might know what you intend to do without understanding why those choices will produce useful evidence.
That is the distinction to examine when improving an MYP Sciences investigation plan. More detail helps only when it makes the investigation clearer, more defensible or easier to carry out.
This guide focuses on MYP Year 5 Sciences Criterion B, called Inquiring and designing. It uses the Year 5 descriptors in the IB Sciences guide, not the Year 3 rubric.
Understand the Achievement Levels First
Criterion B has achievement levels from 0 to 8. Above zero, descriptors are grouped into four bands: 1 to 2, 3 to 4, 5 to 6, and 7 to 8.
The IB assessment overview explains that teachers use a best fit judgment. Completing a checklist does not automatically secure a particular level, and the four strands are not separate scores to average.
Use your teacher’s task instructions alongside the rubric. A planning assessment may have specific equipment, time or investigation constraints. The advice below helps you examine your design; it does not replace those instructions.
What Changes Between 5 to 6 and 7 to 8?
The Year 5 Criterion B descriptors make four important distinctions.
Strand i: The question. At 5 to 6, you describe the problem or question. At 7 to 8, you explain it.
Strand ii: The hypothesis. Both bands require a testable hypothesis and an explanation. The higher band specifies “correct scientific reasoning”.
Strand iii: Variables and data. Both bands require sufficient, relevant data. At 5 to 6, you describe variable manipulation and data collection. At 7 to 8, you explain them.
Strand iv: The method. Both bands require a complete, safe method and appropriate equipment. At 7 to 8, the method must also be “logical”.
The practical implication is to check the reasoning behind your decisions, not simply add more headings. The worked discussion that follows is an application of these expectations, not an additional IB checklist.
Turn a Topic Into an Investigable Question
RevisionDojo’s MYP Sciences guide uses a published teaching example about temperature and catalase activity. We will develop that example here. This is not a graded student submission, and no experimental results are being claimed.
A more measurable formulation of the task is:
How does reaction temperature affect the volume of oxygen produced per minute when catalase breaks down hydrogen peroxide?
This identifies what changes and what will be measured. It also connects the measurement to the science: catalase converts hydrogen peroxide into water and oxygen, as explained by RCSB Protein Data Bank’s catalase resource.
Your actual plan still needs to identify the enzyme source, temperature settings and measurement conditions. Select these with your teacher rather than copying a range from an unrelated investigation.
To explain the question, connect the independent variable to the scientific process. Here, the issue is not simply whether warm and cold samples behave differently. It is how temperature affects enzyme activity, using oxygen production as the indicator.
Write a Hypothesis That Explains the Pattern
A prediction that oxygen production will increase with temperature is testable, but it may be scientifically incomplete.
OpenStax’s explanation of collision theory connects warming with a greater proportion of molecules having enough energy to react. Its enzyme chapter explains why high temperatures can eventually disrupt enzyme structure and function.
Applied to the published catalase task, the reasoning could be developed as follows:
Within a range where catalase remains functional, warming is expected to increase oxygen production per minute because more molecular encounters have sufficient energy for reaction. At sufficiently high temperatures, activity may fall because denaturation changes the enzyme’s structure and disrupts the active site’s function.
That is a reasoned prediction, not a result. Your investigation may cover only part of the predicted pattern.
Do not announce a particular optimum temperature without evidence for the enzyme preparation and conditions you are using. Nor should you describe an enzyme as dying: the relevant explanation concerns changes to its structure and activity.
Check the connection between your prediction and your method. A hypothesis about a rise followed by a decline needs a temperature range capable of investigating that possibility, subject to the available equipment and safety restrictions.
Explain Variables Through Actions, Not Labels
A variables list is a starting point. The design becomes clearer when each entry answers three questions: What is the variable? How will you manage it? Why does that matter?
For the catalase investigation, apply that structure carefully.
Independent variable: reaction temperature. State the selected temperatures, how the reaction mixture will reach them and how you will check them. The temperature displayed on a water bath is not, by itself, evidence that the reacting mixture has reached that temperature.
Dependent variable: oxygen production over a defined interval. Identify the gas collection apparatus, the units and the exact measurement window. Dividing collected volume by elapsed time gives an average rate over that interval. Do not describe a final volume reading as an instantaneous rate.
Controlled variables: conditions that could offer another explanation. Specify the enzyme preparation, enzyme concentration and volume, hydrogen peroxide concentration and volume, pH, and observation period. Explain how each will be kept consistent.
For an enzyme extract, one proposed approach is to use equal measured volumes from the same well mixed preparation, provided it remains stable throughout the experiment. This connects a concrete action to its purpose: making the enzyme supply comparable between trials.
For pH, the scientific justification is particularly clear: changes in pH can affect enzyme function. Allowing pH to vary with temperature would make the comparison harder to interpret.
The same logic applies throughout your plan. Naming a control is less useful than explaining how your procedure actually maintains it.
Plan Sufficient Data Before Collecting Any
Ask whether your planned measurements can answer the question you have written.
For this investigation, consider both the spread of temperature settings and repeated trials at each setting. Widely separated settings may miss a change in the pattern. Closely grouped settings may investigate too narrow a range to address your hypothesis.
Repeats serve a different purpose: they let you examine how consistently the procedure produces measurements under the same conditions. Taking several readings from one reaction is not equivalent to running several fresh reactions.
There is no universal number of settings or repeats specified in the Year 5 Criterion B descriptor. Your teacher may set requirements for the task. Explain why your proposed dataset is sufficient within those constraints.
Prepare an empty results table before starting. Include units, space for every trial and any conditions you need to record. This can reveal a mismatch between what your question requires and what your method actually measures.
Make the Method Repeatable and Logically Ordered
Read your method as though you have never seen the equipment before. Where would you need to guess?
For the catalase task, check three parts of the procedure.
Preparation. Identify the enzyme source, solution concentrations, measured quantities and suitable measuring equipment. Explain how you establish the intended temperature before the reaction begins.
Measurement. Specify the event that starts the reaction and the timer. Explain how gas collection begins without an avoidable delay, when readings are taken and how temperature is maintained during measurement.
Repeating the investigation. Explain how fresh samples are prepared, how equipment is reset and how you keep the procedure consistent across trials and temperatures.
These details make the method usable. Logical order also matters: checking the temperature after the reaction has finished cannot establish the temperature throughout the measurement period.
Safety belongs within the relevant steps. Identify the risks associated with the reagents, heated water and glassware, then follow the precautions in your school’s risk assessment. Have your teacher approve the procedure before attempting it.
A diagram can clarify the apparatus, but it should support the written quantities, timings and instructions rather than replace them.
Pilot the Method and Record Your Decisions
A small trial, where your teacher permits one, can reveal whether the gas volume is measurable, whether the collection apparatus works and whether the proposed timing is practical.
Lanterna’s science investigation planning advice recommends preliminary experiments and keeping a record as the work develops. Its advice is direct:
“Make sure to record everything you do as you go along.”
Revision Village’s investigation resources similarly organise planning around stages that include a focused question, a method and a feasibility check.
Both resources discuss DP internal assessments. The planning habits are useful here; their assessment frameworks should not be transferred to MYP Sciences.
Record what you changed after a trial and why. A revised measurement window or improved temperature control should solve an identified problem, not simply make the procedure look more elaborate.
Check the Whole Investigation, Not Just Each Section
Before submitting, read the question, hypothesis, variables and method together.
Does the hypothesis address the question? Will your measurements reveal the predicted relationship? Are the controls maintained by actual instructions? Could another student follow the procedure without asking you to fill in missing details?
These are useful checks because they expose contradictions that are easy to miss when editing one section at a time.
For further practice and explanations, explore Koncepts for MYP students. Use that support to strengthen your understanding while keeping the investigation decisions and submitted work your own.
A stronger Criterion B plan does more than describe an experiment. It makes clear why the experiment is worth doing, how the evidence will be collected and why the comparison should be meaningful.
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