CCEA A2 Life and Health Sciences: where the 400 marks across Organic Chemistry, Medical Physics, Sound and Light and Genetics go, the unit and charge-notation slips that cost marks, and how to plan the QWC question in each paper.
Short Answer & Terminology, Genetic Crosses & Inheritance Trees, Statistical Analysis (Chi-Squared), Data Interpretation & Trends, QWC Extended Response
评级
A*ABCDE
计算器规定
No subject-specific calculator restriction is stated beyond the general CCEA and JCQ rules: calculators are permitted for the numeric calculations across all four papers (radioactive decay, acoustic impedance, lens power, chi-squared testing), but must not have any retrievable information stored in them and must not offer symbolic algebra manipulation, language translation, or communication with other machines or the internet.
AO1: AO1: demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures. (45%)
AO2: AO2: apply knowledge and understanding of scientific ideas, processes, techniques and procedures in a range of theoretical and practical contexts, and when handling qualitative and quantitative data, to solve scientific problems. (33%)
AO3: AO3: analyse, interpret and evaluate a range of scientific information, ideas and evidence to make judgements and reach conclusions, including in relation to issues, and to refine practical design and procedures. (22%)
用途: Keep the shown method that earns credit visible on the page, even where a later step goes wrong.
使用时机: Multi-step Medical Physics and Sound and Light calculations, decay constants, acoustic impedance, lens power, dosimetry.
步骤
Write the formula and the substitution with units on paper first, then key the numbers into the calculator only for the arithmetic step, and copy the result back onto the page.
考试提示: The calculator performs only the arithmetic here, live during the exam, it holds no stored formulae or notes.
Memory recall for converted intermediate values
Casio fx-991EX ClassWiz (or equivalent)
用途: Hold a converted value, a distance in metres or a time in seconds, needed again later in the same question.
使用时机: Any question where an early unit conversion feeds into a calculation two or three steps later.
步骤
Calculate the converted value, press the memory store key and a letter to save it, continue with the rest of the working, then recall it with the same letter when needed again.
考试提示: Clear the memory at the start of the exam and only store values calculated live during the paper, this is not a saved program.
Statistics mode for chi-squared totals
Casio fx-991EX ClassWiz (or equivalent)
用途: Total observed and expected frequencies quickly when setting up a chi-squared calculation.
使用时机: Genetics questions asking for a chi-squared goodness-of-fit test on cross ratios.
步骤
Enter the observed and expected values into statistics mode to get quick running totals, then complete the chi-squared formula and degrees of freedom by hand on the page.
考试提示: This uses only the values given in the question, entered live, nothing is stored from before the exam.
Drawing reflux apparatus with the water connections reversed, or an open top missing from the condenser.
如何避免: Draw the condenser with an open top, water entering at the bottom and leaving at the top, and label both connections explicitly.
2medium涉及分数: 1Organic chemistry, spectroscopy
Writing mass spectrometry fragment ions without their charge, for example C2H5 instead of the correctly charged fragment.
如何避免: Write the fragment in square brackets with its explicit positive charge shown outside the bracket.
3high涉及分数: 2Medical physics, radioactivity
Calculating a radioactive source's activity without first correcting for background radiation.
如何避免: Subtract the background count rate from every reading before using it in a decay calculation.
4medium涉及分数: 2Medical physics, calculations
Rounding an intermediate value early in a decay constant or half-life calculation, for example straight after converting hours to seconds, letting the final answer drift.
如何避免: Carry full calculator precision through every intermediate step and only round the final answer to the number of significant figures asked for.
5high涉及分数: 3Genetics, dihybrid crosses
Writing single letters for gametes in a dihybrid cross instead of the correct paired alleles.
如何避免: Write every gamete as a circled pair of alleles, one from each gene, generated systematically before filling in the Punnett square.
6medium涉及分数: 3Genetics, statistical testing
Concluding a chi-squared test with an informal statement instead of an explicit null hypothesis and a conclusion referencing the critical value and degrees of freedom.
如何避免: State the null hypothesis formally before calculating, and finish by comparing the calculated statistic with the critical value at the stated degrees of freedom, then state whether the null hypothesis is rejected.
7medium涉及分数: 2Sound and light, hearing
Confusing decibel sound intensity level with perceived loudness measured in phons when reading logarithmic hearing graphs.
如何避免: Check which scale the question and the graph axis actually use before comparing values, decibels and phons are not interchangeable.
8high涉及分数: 4QWC, extended response
Giving unbalanced Quality of Written Communication answers that cover only one side of a prompt, or that avoid the specific technical vocabulary the mark scheme expects.
如何避免: List every bullet point in the question stem before writing, and use the exact technical terms the topic requires rather than a general paraphrase.