Criterion B in chemistry is about designing a fair test that you could actually carry out in a lab: one variable changed, one measured, everything else controlled, and the safety thought through.
You say what is being tested and why, using the science behind it.
Your prediction names the variables and is explained with scientific reasoning.
You say how each variable is changed, measured or controlled, and how data will be gathered.
A logical, safe, complete method that someone else could follow and repeat.
A little of the criterion is addressed. Ideas are basic, partly missing, or not linked to the task.
The main points are there but thin. Some explanations are correct; links to the task or evidence are incomplete.
Mostly accurate, well explained and consistently tied to the task, with only small gaps.
Detailed, precise and justified throughout, with ideas connected and applied to new situations or evidence.
A plain-language guide only. Your teacher marks against the official IB level descriptors.
Write a method outline for investigating how concentration of hydrochloric acid affects the rate of reaction with sodium thiosulfate.
Mix different amounts of acid with thiosulfate and see how fast it goes cloudy.
I will change the concentration of hydrochloric acid (0.5, 1.0, 1.5, 2.0 mol/dm³) and measure the time for a cross under the flask to disappear. I will keep 50 cm³ of 0.2 mol/dm³ sodium thiosulfate, 10 cm³ of acid, temperature (20 °C, checked with a thermometer) and the same flask constant. I will repeat each concentration three times and wear eye protection because the acid is an irritant and sulfur dioxide may be released.
Criterion B is Inquiring and designing. It is marked out of 8 across 4 strands (B.i, B.ii, B.iii, B.iv). Criterion B in chemistry is about designing a fair test that you could actually carry out in a lab: one variable changed, one measured, everything else controlled, and the safety thought through.
Choose a dependent variable you can really measure, such as time for a mark to disappear or volume of gas collected. Explain your hypothesis using particle theory: more concentration means more collisions per second. Name the control variables with values (25 cm³ of acid, 20 °C) and say how each is held constant.
A hypothesis that is only a prediction, with no particle explanation. Control variables listed with no values or method. Safety written as be careful rather than a specific hazard and precaution.
Written by CritABCD for study and revision, in our own words. The official MYP Chemistry guide and assessment criteria are published by the International Baccalaureate. Official IB guide ↗