Formulate a research question, identify independent, dependent and controlled variables, and design or improve a method so that it answers the question fairly and safely.
Tę umiejętność sprawdza 18 zadań wzorowanych na arkuszach IB z lat 2022–2026.
(c) A simple set-up was used to compare the conductivity of water samples obtained from the Salton Sea at different depths. The following data were obtained: (i) State the independent and the dependent variable in this experiment. (ii) Suggest two variables,…
Identify the independent variable and the dependent variable in this investigation.
State two variables that should have been kept constant in the four runs.
Discuss the range of the independent variable and the quantity of data in this investigation.
A sample of 0.0120 mol of NO2 was placed in a sealed vessel of volume 1.00 dm3, which was kept at a constant temperature of 35 °C. (i) Suggest a simple way of keeping the vessel at a constant temperature in a school laboratory. (ii) The…
(i) State the independent variable and the dependent variable of the investigation. (ii) Apart from the mass of leaves and the volume of water, suggest two other conditions that should be kept constant for the comparison between boiling times to be valid.
Each beaker used as a chromatography chamber was covered with a watch glass while the solvent rose up the paper. Explain why the chamber has to be covered for the experiment to be properly designed.
The student suspected that the ink contained more than four dyes, and that one of the spots was two dyes that had not separated. Suggest how the student could modify the chromatography experiment to test this idea.
Identify two controlled variables in this investigation.
The iron(II) concentration is found by titrating against a standard solution of potassium manganate(VII), KMnO4. At intervals of a few days, a 20.00 cm3 sample is withdrawn from each flask and made up to 250.0 cm3 with water;…
Suggest one way of extending the investigation so that further recommendations about storing the iron(II) solution could be made.
Suggest why the times measured for equal masses of the two metals are not a valid basis for comparing their reactivity.
The student hypothesized, from theory, that doubling the mass of CuO would double the rate of the catalysed reaction. (i) Suggest why it is important to state a hypothesis before an experiment is carried out. (ii) Explain how collision theory could…
Suggest two variables that should be controlled when mussels are collected and their soft tissue is sampled.
(i) Bronze, an alloy of copper and tin, is used for ship propellers and bearings. Explain, by referring to its structure, why bronze is less malleable than pure copper. (ii) In a separate process, zinc is removed from a copper-zinc alloy by reaction with…
Heat treatment at 90 °C is used to destroy spoilage micro-organisms in pineapple juice. The concentration of vitamin C was measured over 56 days in untreated juice and in heat-treated juice from the same batch. (i) Identify the dependent variable in this…
(i) Identify the dependent variable plotted on the graph. (ii) Calculate the decrease in the concentration of vitamin C, in μg cm−3, caused by the heat treatment. (iii) Calculate the average rate of decrease of the vitamin C concentration in…
A student compares the rate of the reaction between magnesium ribbon and dilute hydrochloric acid at different temperatures by timing how long it takes for a piece of ribbon to dissolve completely. Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g) Suggest two…
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