Examination Feedback Summary GCSE Science June 2014 Series

Transcription

1 Examination Feedback Summary GCSE Science June 2014 Series This examination feedback summary refers to GCSE Biology, Chemistry and Physics. It provides a summary of the common issues identified in student responses in the June 2014 series for both the Foundation and Higher tier papers. Please note that some issues refer to the common questions found on both tiers. A selection of questions that students found most challenging, along with their responses and examiner commentaries, accompanies this summary. This summary is not a substitute for detailed feedback on each individual question which can be found in the Report on the Exam, available on e-aqa or on the past papers section of our website.

2 GCSE Biology (B1, B2, B3) Feedback from 2014 series The majority of students were able to recall knowledge where simple facts or processes were required. However, there were areas where more complex processes were misunderstood. Applying knowledge to a new context was difficult for many students. The following are some examples of where examiners thought that students did less well than expected on biological knowledge and understanding. Many students: could not give the third group of living organisms when given animals and microorganisms. Many students gave subgroups of those already given classification (BL1FP Q1b) had a poor understanding of diffusion (BL2FP Q8) did not know that fertilised egg cells divide by mitosis once the gametes have fused (BL2HP Q6ci) could not identify the xylem, the phloem and stomata (BL3FP Q4a) did not know why too much sugar can make a person overweight (BL1FP Q3bi) a common misconception was that sugar contains fat did not know that amino acids were the product of protein digestion (BL2FP Q7ai) did not know that hydrochloric acid is responsible for the low ph in the stomach (BL2FP Q7c) did not know the correct scientific name for sex cells (BL1FP Q5ai) and were unable to identify the method of producing calves shown in the diagram as embryo transplantation (BL1FP Q5bii). Students did not include information about the effect of the fathers genes in terms of producing variation during sexual reproduction (BL1FP Q5biii) had a lack of clear knowledge of thalidomide as detailed in the specification (BL1HP Q6) showed excellent knowledge of genetic engineering but some students were not clear as to what genes were cut from and when describing where and when the gene should be transferred (BL1HP Q8a) had a misunderstanding about the use of, and problems associated with, genetically engineered plants (BL1HP Q8b) were unable to correctly identify a symbol that represented a sperm cell (BL2FP Q5bi) did not know that DNA was the chemical substance that made up genetic material (BL2HP Q6ciii) did not know the names of the gap between two neurones and how the information passes across the gap simple reflex actions (BL1FP Q7bi and bii) could not name the different parts of the heart (BL3FP Q1bi) could not identify another type of blood vessel that has valves (BL3FP Q1biii) were not familiar with what happens when red blood cells are put into water (BL3FP Q3bii) did not know that glucose in dialysis fluid is at the same concentration as in the blood (BL3FP Q5aiv) could not explain vasodilation as a process to aid temperature control could not interpret energy flow in food chains (BL1FP Q8bi). They did not correctly identify which food chain had the greatest proportion of biomass and energy transferred from plants 2 of 8

3 to humans. A common misconception was that longer food chains meant organisms would gain more biomass for the humans (BL1FP Q8bii) did not understand how energy is released as heating during the decay process (BL1FP Q10) did not know the process that makes lactic acid in an athlete s muscles (BL2FP Q9) showed confusion between the two theories of Darwin and Lamarck (BL1HP Q7) particularly the timescales involved could not describe the study of organisms using a transect (BL2FP Q2), in particular that repetition of the transect would improve validity did not understand the significance of the horizontal line in terms of the photosynthesis rate not increasing light intensity and photosynthesis (BL2FP Q6b). Some students also used incorrect terminology by stating the line was straight when they meant horizontal still do not understand that although repeats are needed in experimental designs they do not improve accuracy (BL2FP Q7bii) Specific exam issues Imprecise communication An example was what an allele is and what recessive means. There was confusion between an allele being inherited and being expressed (BL2HP Q6ai) Poor use of terminology (BL1HP Q4di) many students using words like treating, curing or fighting, rather than killing pathogens and in (BL1HP Q4dii) bacteria becoming immune or infections developing resistance Spelling errors For example words such as glygogon or glucogen when describing how the body responds when the blood glucose concentration begins to decrease (BL3HP Q6b) make answers too ambiguous to award marks. Quality of written communication (QWC) questions Students wrote excessive amounts in both tiers. Many high scoring answers on the Unit 1 QWC were provided by students who wrote a small amount and kept to the point. Explain questions In general students did not realise the meaning of this command word and described rather than explained. For example in BL1FP Q2bii many students described the diagram rather than explaining and linking the information about more light being needed to allow more photosynthesis In BL3FP Q5b students quoted information from the stem without expanding on their explanation Investigative skills Students often had difficulty applying their knowledge of other aspects of the specification to experimental methodology and the interpretation of results (BL2HP Q4) There was much confusion between a fair test and reliability (BL3FP Q4bii) Graphical skills There was: some misunderstanding of the scales on a graph (BL1FP Q6b) poor use of evidence from the graph to explain the pattern shown (BL2FP Q9) misreading of figures off the graph mainly due to misinterpretation of the scale where 1 small square represented 0.2 units (BL2FP Q9) 3 of 8

4 lack of comparative answers (BL2FP Q9bii) imprecise use of terminology when describing graphs which lost many marks. Mathematical skills Many students used incorrect expressions of probability (BL2FP Q5bii) Many students were unable to calculate percentages (BL3FP Q6ai) It appeared many students did not have access to a calculator 4 of 8

5 GCSE Chemistry Feedback from 2014 series Chemistry topics Atoms, ions and molecules students often used these terms interchangeably (CH2HP Q2, CH2HP Q4, CH2HP Q5b, CH3FP Q1b). Ores many students did not appreciate that an ore has sufficient metal to make it economical to extract by definition (CH1FP Q5ai). Testing for unsaturated hydrocarbons with bromine water few students demonstrated knowledge of this chemical test, with many simply describing results from data given in the question (CH1FP Q6ai). Gas chromatography was not well understood, with many students writing about boiling point being the reason for compounds separating (CH2FP Q6c / CH2HP Q1c). Extracting gases from air despite a similar question on a previous paper, students did not understand the implications of temperature on the state of an element or compound, for instance that carbon dioxide would be a solid in this scenario (CH1HP Q6). Electronic structure many students did not select the correct electronic structure for an ammonia molecule (CH2FP Q4b / CH2HP Q7b). Ionic bonding some students referred to sharing electrons or covalent bonding when describing potassium chloride (CH2FP Q4d). Comparing chlorine and sodium chloride a lot of students were able to link the strength of bonds or forces with the state of a substance at room temperature, but many found it more challenging to describe the bonding and structure accurately (CH2FP Q7 / CH2HP Q2). There were a lot of references to the chlorine-chlorine bonds being weak and so easily broken, which was why chlorine is a gas. Cracking many students did not understand that cracking can be used to break down hydrocarbons (CH1FP Q4ciii) and suggested that it could be used to separate mixtures of hydrocarbons (CH1HP Q7aiv). Flame tests few students knew how to carry out a flame test, possibly confusing flame tests with the reactions of alkali metals with water (CH3FP Q6ai). Hydration of ethanol there was confusion with students describing dehydration, dissolving or saturating (CH1HP Q2ai). Calculations Make sure students have a calculator some students wrote correct calculations in their working, but failed to calculate an answer (CH2FP Q5ci). Students should be confident with using their calculators errors were introduced by not using brackets where appropriate (CH3FP Q3bii). Calculating mean values students must remember to remove anomalous results before calculating a mean (CH2FP Q5bii, CH1FP Q3bii). Students should think whether a number is realistic when writing their answer yields of 133% were seen in student responses (CH2HP Q4biv). 5 of 8

6 Titration calculations many students scored no marks because they did not recall how to carry out a titration calculation (CH3HP Q4d). Experimental skills When asked to write conclusions that could be made from a paper chromatography experiment, some students simply wrote observations (CH2HP Q6b). Graphical skills Students used imprecise language to describe the shape of a graph, rather than the relationship that the graph represented (CH3FP Q4b). Repeating stems / reading instructions Students often gave information from the stem of a question as their answer (CH1FP Q6aiii/ CH1HP Q3aiii, CH1FP Q4aii, CH2HP Q3bii, CH3FP Q7c/CH3HP 1c, CH3HP Q7c) including, for example, that distillation is not economic because it is expensive. A lot of students wrote about things that the question asked them not to include, describing weighing errors when the question specifically stated not to refer to weighing errors (CH1HP 5bii). Precise language When asked to explain, many students simply recalled facts without explaining why they are important. When asked why iodine does not react with sodium bromide solution, many simply referred to the positions of elements in Group 7 of the Periodic table, without answering why a reaction would not take place (CH3FP Q1dii). 6 of 8

7 GCSE Physics Feedback from 2014 series Physics topics Kinetic theory (PH1FP Q9) many students did not refer to forces in their answer, which limited access to higher marks. Velocity time graphs (PH2FP Q8aiii) there was some confusion in student responses over what they are and what the gradient represents. Momentum (PH2FP Q4, PH2HP Q5) student responses often lacked understanding of this topic. Calculation of momentum in collisions was not done well (PH2HP Q5b). Static electricity (PH2FP Q7/PH2HP Q1) not well answered with little understanding shown in part (b)(ii). Life cycle/mass of stars (PH2HP Q2bii / Q2biii) students wrote about visiting the star and needing weighing machines. Radiation/radioactivity (PH2HP Q6) lack of precise answers and (PH3FP Q7d) poor understanding of effects on body (ie details should be at cellular level rather than just harmful ) RCCB (PH2HP q7c) there was a lack of understanding about what an RCCB is and how it works. Lenses and eyesight (PH3FP Q3) students did not understand what type of lens is used to correct eyesight defects such as short sight and did not understand what causes each of these eyesight defects. Electromagnets (PH3HP Q8d) and transformers (PH3FP Q9a/PH3HP Q3a) student responses demonstrated a lack of understanding of these topics. Echoes (PH3HP Q1b) many students forgot to halve the distance to take account of the reflected signal being an echo and consequently did not gain marks. Calculations Make sure students have a calculator that is capable of carrying out sine functions. Know and remember the units in physics equations a number of students dropped marks for not giving the unit or for using the wrong case for the unit letters (PH1FP Q2b, PH1HP Q7c, PH2FP Q8bi/PH2HP Q3bi, PH3HP Q4a). Efficiency students lost marks for giving efficiency as a fraction with a % sign or for calculating efficiency as a percentage but not including the % sign (PH1FP Q1b). Choose the correct equation, substitute values into the equation, then rearrange and calculate the answer. Some marks can be given if the calculation is wrong as long as the values were originally correctly substituted before the rearrangement (see general note on report PH1HP). Significant figures students did not gain marks in calculations because significant figures were incorrectly rounded (PH1HP Q4aii). Rounding students lost marks by rounding numbers part way through a calculation, thus introducing a rounding error in their final answer. 7 of 8

8 Acceleration the unit includes a square, but some students interpreted this as an instruction to square their answer (PH2FP Q2b). Sine functions students should be comfortable with inverse sine PH3HP Q7b. Experimental skills Control variables and experimental techniques skills demonstrated well in ISAs did not seem to be transferred to the written papers (PH1HP Q8bii, PH1FP Q5ai). Graph drawing Lines of best fit students did not gain marks by incorrectly drawing lines of best fit. Graphs were not drawn carefully and caused marks to be lost (PH2FP Q2aii, PH2HP Q4aiii). Reading values from graphs students did not gain marks by misreading the scale or reading from the wrong axis. Understanding the reason for choosing a graph type continuous, categorical variables etc (PH1FP Q5aii, PH1HP Q8bii). Quality of written communication (QWC) questions Students often wrote essay plans for their answers good answers can usually be written in a limited number of lines and students do not need to produce a plan of their answer (PH1FP Q9/PH1HP Q2). 8 of 8