IB Chemistry SLTopic 8 — Exploring and DesigningInternal assessmentPractical skill~12 min read
Exploring
Almost every strong investigation starts as an ordinary school experiment with one extra question attached to it. You are not being asked to invent new chemistry — you are being asked to notice something worth comparing.
📚 What you need to know
Exploring means using curiosity and existing chemistry to reach a focused research question and a testable hypothesis.
A strong investigation has one independent variable and one dependent variable, explored in depth.
Background research gives you the theory, a literature value to compare against, and a workable method.
A research question must be focused and specific, naming the chemicals, the range of the independent variable, and what is being measured.
A hypothesis is not a guess. Use “if…, then…, because…”, and let the “because” carry the chemistry.
The justification must rest on established principles — collision theory, intermolecular forces, thermodynamics.
Check feasibility early, and be willing to refine the question once you have read around it.
From a broad interest to a question
The gap between “I find enthalpy interesting” and a research question worth four weeks of work is filled by reading. Research is not decoration you add at the end; it is the step that tells you which comparison is worth making.
Each stage cuts something away. By the end you have a question narrow enough to answer properly in the time you actually have.
Where to look
What you are looking for
Your notes and textbook
the underlying theory that will justify your prediction
The IB data booklet
accepted values to compare your result against
Reliable chemical databases
physical and thermodynamic data for compounds you might use
Standard practical methods
a technique that is known to work in a school laboratory
Struggling for an idea is completely normal, and the usual cure is not more staring. Look at a result from a class experiment that surprised you, take a standard practical and swap one component (a different acid, a different catalyst), or apply a familiar measurement to something real — the acid content of different brands of vinegar, for instance.
What makes a research question focused
“How does temperature affect reaction rate?” is a topic, not a question. It could be answered by a textbook. A research question has to commit to specifics: which reaction, what range, measured how.
The range does real work. Committing to 20–60 °C forces you to justify why not colder and why not hotter — which is a design mark you can claim later.
Beware the two-variable question. “How do concentration and temperature affect the rate of reaction?” is two investigations pretending to be one, and neither will be done properly. Pick one factor and go deep.
Turning a prediction into a hypothesis
“If concentration increases, the rate will increase” is a prediction. It is probably right, and it earns very little, because anyone could have said it. A hypothesis adds the reason, drawn from chemistry you can name.
Test your “because” by asking whether it could be wrong. “Because the rate goes up” cannot be wrong — it is the prediction again. “Because there is a higher frequency of effective collisions” is a claim about mechanism, and that is what is wanted.
WORKED EXAMPLE
A student proposes the research question “How does concentration affect the rate of reaction?” Explain why this is unsuitable and rewrite it as a focused research question.
What is wrong with itIt names no reaction, no chemicals and no range, so it could not be repeated by anyone else and there is nothing to justify.a topic, not a questionWhat to addThe exact reaction, the range of the independent variable, and how the dependent variable will be measured.A focused version“What is the effect of hydrochloric acid concentration, from 0.5 to 2.5 mol dm⁻³, on the initial rate of reaction with 2.0 cm strips of magnesium ribbon?”Notice that the fixed quantity of magnesium is in the question. That is not padding — it is what makes the comparison fair.
WORKED EXAMPLE
Write a hypothesis for the focused research question above, using the “if, then, because” structure.
Ifthe concentration of the hydrochloric acid is increased…thenthe initial rate of reaction with the magnesium will increase…becausea higher concentration means more acid particles in the same volume, so there is a greater frequency of collisions between H⁺ ions and the magnesium surface, and therefore a greater frequency of successful collisions per second.prediction plus a named principle: collision theoryIf you can add what shape you expect the graph to be, do — it gives you something specific to test against later.
WORKED EXAMPLE
A student wants to investigate “how temperature and catalyst concentration affect the decomposition of hydrogen peroxide”. Identify the problem and suggest how to fix it.
The problemThere are two independent variables. Any change in rate could be caused by either one, so no conclusion about either can be justified.two investigations in one questionThe fixChoose one factor and hold the other constant as a controlled variable.“What is the effect of potassium iodide concentration, from 0.10 to 0.50 mol dm⁻³, on the initial rate of decomposition of 1.0 mol dm⁻³ hydrogen peroxide at 25 °C?”Temperature has not disappeared — it has been promoted to a controlled variable, which is exactly where it belongs.
💡 Exam tip
Frame the investigation as a comparison; it is the easiest way to show insight.
Put the range of the independent variable inside the research question.
Use if, then, because, and make the “because” name a chemical principle.
Cite where a literature value came from — you will need it to judge your result later.
Check feasibility before you commit: the right equipment, the right chemicals, enough time.
Refining a question after reading is a strength, not a failure.
⚠️ Common mix-up
Two independent variables in one research question. Choose one and control the other.
A “because” that repeats the prediction instead of explaining it.
Leaving the range out of the question, so nothing forces you to justify it.
Treating research as a bibliography. It should shape the question, not decorate it.
Choosing an idea you cannot actually run with school equipment in the time available.
Up next: Designing Investigations — a good question deserves a method precise enough that another chemist could follow it exactly and get your numbers back.
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