Exploring in Chemistry (DP IB Chemistry): Revision Note
Exploring in Chemistry
This is the creative start of the process where you act like a true scientist.
It involves using your curiosity and existing chemical knowledge to formulate a focused research question and a testable hypothesis.
It requires independent thinking and consulting a variety of sources to understand the scientific context behind your idea and to make a clear, scientifically-justified prediction.
Developing your investigation
Demonstrate independent thinking, initiative, and insight
The best investigations often start with a simple question about a standard experiment.
For example, "measuring the enthalpy of combustion of an alcohol."
You can show insight by framing it as a comparative investigation:
"To what extent does the position of the hydroxyl group (propan-1-ol vs. propan-2-ol) affect its enthalpy of combustion?"
This shows you are thinking about the links between structure and energy.
A common mistake is trying to investigate too many variables at once.
A strong investigation explores the relationship between one independent variable and one dependent variable in depth.
Avoid questions like "How do concentration and temperature affect the rate of reaction?".
Choose just one factor and investigate it thoroughly.
Consult a variety of sources
Before you can formulate a high-quality question, you need background information.
This is a crucial research step.
Good research helps you to:
Understand the underlying chemical theory.
Find established scientific values for comparison.
Identify a suitable method for collecting data.
You can use various resources, including:
Your notes
Your textbook
The IB data booklet (opens in a new tab)
Reliable online chemical databases, e.g. the NIST Chemistry WebBook (opens in a new tab) or PubChem (opens in a new tab).
This research provides the scientific context for your investigation, showing that you understand the chemistry behind your question.
Formulate research questions and hypotheses
A research question (RQ) must:
Be focused
Be specific
Clearly state the link between the independent variable and the dependent variable.
An RQ like "How does temperature affect reaction rates?" is too general.
A focused RQ specifies the reaction:
"What is the effect of temperature (20°C to 60°C) on the rate of reaction between 0.1 M HCl and 1.0 g of CaCO3 chips?"
A hypothesis is not a guess.
It is a clear, testable statement that predicts the outcome and includes a scientific justification.
The best hypotheses follow an "If..., then..., because..." structure.
State and explain predictions using scientific understanding
The "because" part of your hypothesis is where you explain your prediction.
This explanation must be based on established chemical principles, such as collision theory, intermolecular forces, or thermodynamic principles.
A hypothesis like "If concentration increases, the rate will increase" is just a prediction.
To make it a valid scientific hypothesis, you must add the justification:
"...because according to collision theory, there will be a higher frequency of effective collisions."
Worked Example
Exploring an enthalpy change investigation
Broad idea:
I am interested in the energy changes that happen during acid-base neutralisation reactions.
Consulting sources and gaining insight:
My textbook states that neutralisation reactions are exothermic.
Section 12 of the IB data booklet (opens in a new tab) shows the standard enthalpy of neutralisation for strong acids and strong bases is approximately -57 kJ mol-1.
Further online research reveals that the enthalpy of neutralisation for weak acids is consistently less exothermic.
Formulating the research question:
"What is the effect of acid strength on the standard enthalpy of neutralisation when reacting a strong base (aqueous sodium hydroxide) with a strong acid (hydrochloric acid) versus a weak acid (ethanoic acid)?"
Formulating the hypothesis:
If ethanoic acid (a weak acid) is neutralised instead of hydrochloric acid (a strong acid)...
then the experimentally determined enthalpy of neutralisation will be less exothermic...
because some of the energy released by the formation of water must be used to provide the energy required for the complete dissociation of the weak ethanoic acid molecules.
Worked Example
Exploring a yield investigation
Broad idea:
I want to investigate the factors that affect the amount of product I can make in a reaction.
Consulting sources and gaining insight:
Textbooks define percentage yield as the ratio of experimental yield to theoretical yield.
It is a measure of a reaction's efficiency.
I find a common school experiment is the synthesis of hydrated copper(II) sulfate crystals by reacting solid copper(II) carbonate with sulfuric acid.
A key concept is the limiting reactant, where the reaction stops when one reactant is completely used up.
This suggests that reaction time might be a key factor in achieving the maximum possible yield.
Formulating the research question:
"What is the effect of reaction time (from 2 to 10 minutes) on the percentage yield of hydrated copper(II) sulfate crystals formed from reacting a fixed mass of excess copper(II) carbonate with a fixed volume and concentration of sulfuric acid?"
Formulating the hypothesis:
If the reaction time is increased...
then the percentage yield of the crystals will increase up to a certain point and then plateau...
because more time allows for the reaction to proceed further towards completion.
However, the yield will stop increasing once the limiting reactant (sulfuric acid) has been entirely consumed, at which point the maximum theoretical yield has been reached.
Worked Example
Exploring rates of reaction
Broad idea:
I want to see what makes reactions go faster. I know catalysts speed up reactions.
Consulting sources and gaining insight:
The syllabus explains that catalysts provide an alternative reaction pathway with a lower activation energy.
Collision theory states that a higher concentration of a reactant increases the rate of reaction. Does the same apply to the concentration of a catalyst?
Researching the decomposition of hydrogen peroxide (H2O2 (aq)) shows it is a slow reaction that can be catalysed by various substances, including potassium iodide (KI (aq)).
Formulating the research question:
"What is the relationship between the concentration of the potassium iodide catalyst (from 0.1 M to 0.5 M) and the initial rate of decomposition of a 1.0 M hydrogen peroxide solution?"
Formulating the hypothesis:
If the concentration of the potassium iodide catalyst is increased...
then the initial rate of reaction will also increase proportionally...
because a higher concentration of the catalyst provides more active sites or catalyst ions available to form the activated complex, increasing the frequency of successful collisions per unit time.
Examiner Tips and Tricks
Struggling for an idea is normal.
Good starting points include:
A surprising or unexplained result from a class experiment.
Investigating a different aspect of a standard lab, such as using a different catalyst or acid.
Applying a chemical concept to a real-world product, like the concentration of acid in different brands of vinegar.
Check feasibility first.
Always consider if you have the right equipment, chemicals, and time to actually carry out your investigation.
A great idea is not useful if it's not practical in a school lab.
Be prepared to refine your idea.
Your initial research might show that your first idea is not possible or practical.
Don't be afraid to change your RQ based on what you learn.
This is part of the scientific process.
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