Development of Practical Skills in Chemistry | OCR A-Level Chemistry B (Salters) (H433)
Development of Practical Skills in Chemistry
- 166 questions
- 12 subtopics
- Practical skills, examined on all three papers
- Component 01, Component 02 and Component 03
The practical strand that runs through the whole course and can be examined in writing on any of the three papers, with most weight on component 03: planning an experiment, choosing and using apparatus, handling significant figures and uncertainties, drawing conclusions from graphs, and the twelve practical activity groups..
It covers planning experiments, implementing: apparatus, units and recording data, significant figures and titration calculations, graphs, gradients and drawing a conclusion, anomalous results, precision, accuracy and types of error, calculating uncertainties and improving a method, hazards, risk and control measures, recording, processing and judging data, measuring pH, mass and volume, and choosing an indicator, reflux, distillation, purification and the standard tests, pAG1 to PAG6: moles, enthalpy, qualitative analysis and organic synthesis and pAG7 to PAG12: electrochemistry, rates and pH.
Sample questions from Development of Practical Skills in Chemistry
Answer each one closed book first, then open the answer.
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Planning experiments
Why is a gas syringe usually a better choice than collecting a gas over water?
Show the answer
A gas syringe measures the full volume produced even for gases that dissolve in water, such as carbon dioxide or ammonia, whereas collection over water loses some of the gas to solution. -
Implementing: apparatus, units and recording data
How should the columns of a results table be headed?
Show the answer
Each heading gives the quantity and its unit, separated by a solidus, for example volume of acid / cm³. -
Graphs, gradients and drawing a conclusion
What determines the unit of a gradient?
Show the answer
The gradient takes the unit of the vertical axis divided by the unit of the horizontal axis. -
Anomalous results, precision, accuracy and types of error
Which type of error is reduced by repeating a measurement and averaging?
Show the answer
Only random error is reduced, because positive and negative deviations tend to cancel; a systematic error remains unchanged. -
Hazards, risk and control measures
Why is concentrated sulfuric acid always added to water rather than water to acid?
Show the answer
Dilution is strongly exothermic, and adding water to the acid releases the heat in a small volume, which can boil and spit corrosive liquid out of the vessel. -
Recording, processing and judging data
What is the advantage of following pH with a probe on a data logger rather than reading a meter by eye?
Show the answer
The logger records many readings per second automatically, capturing the rapid change near the end point that a person reading by eye would miss. -
Reflux, distillation, purification and the standard tests
How is a solid purified by recrystallisation, and why is the minimum volume of hot solvent used?
Show the answer
The impure solid is dissolved in the minimum volume of hot solvent, filtered hot, then cooled so that crystals of the product form and are filtered off; using the minimum volume ensures the solution is saturated so that the maximum amount of product crystallises on cooling. -
PAG1 to PAG6: moles, enthalpy, qualitative analysis and organic synthesis
What would you observe on heating an impure sample of an organic solid in melting point apparatus?
Show the answer
It would begin to melt below the true melting point and melt gradually over a range of several degrees rather than sharply.
The 12 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Planning experiments | Recall questions on independent, dependent and control variables, fair testing, and choosing conditions and apparatus before starting. | 21 |
| Implementing: apparatus, units and recording data | Recall questions on converting between cm³, dm³ and m³, the units of concentration and amount, and recording readings as they are taken. | 22 |
| Significant figures and titration calculations | Recall questions on how many figures a calculated result may carry, standard form, mean titres, and working a titration through to a concentration. | 9 |
| Graphs, gradients and drawing a conclusion | Recall questions on lines of best fit, interpolation and extrapolation, calibration curves, gradients and tangents, and tying a conclusion to the data. | 16 |
| Anomalous results, precision, accuracy and types of error | Recall questions on spotting an anomalous titre, precision against accuracy, and random against systematic error. | 8 |
| Calculating uncertainties and improving a method | Recall questions on percentage uncertainty, combining uncertainties, weighing by difference, and reducing heat loss in a calorimetry experiment. | 17 |
| Hazards, risk and control measures | Recall questions on the hazards of the common reagents, corrosive against irritant, fume cupboards, and why eye protection is worn throughout. | 8 |
| Recording, processing and judging data | Recall questions on what a complete record contains, using a spreadsheet to process results, primary against secondary data, and judging a source. | 16 |
| Measuring pH, mass and volume, and choosing an indicator | Recall questions on the resolution of a burette and a balance, making up a standard solution, and matching an indicator to a titration. | 12 |
| Reflux, distillation, purification and the standard tests | Recall questions on reflux and distillation, separating and drying an organic layer, recrystallisation, melting point, Rf values and the standard test-tube tests. | 14 |
| PAG1 to PAG6: moles, enthalpy, qualitative analysis and organic synthesis | Recall questions on the moles determination, enthalpy measurement, Group 2 qualitative analysis, and preparing and purifying an organic product. | 13 |
| PAG7 to PAG12: electrochemistry, rates and pH | Recall questions on the electrochemical cell experiment, continuous monitoring and initial rates, Arrhenius plots, and distinguishing acids by pH. | 10 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Chemistry B (Salters) Active Recall Guide
Every topic, not just this one. 3,430 questions with their answers.