1. Gaining QWC* marks in Science *quality of written communication
Writing for different purposes.

2. The sorts of questions you may be asked:
Evaluate, in terms of cost and energy efficiency, the use of two types of light bulb.
Suggest an explanation for the development of these different species.
Use information from the article to discuss the arguments for and against allowing doctors to experiment with human fertilisation techniques.

3. Writing for different purposes
To Evaluate – to weigh up evidence in order to reach a judgement
To explain – to offer reasons how or why
To discuss – to explore and compare different ideas

4. Writing to evaluate Question from a past paper
The table gives data about two types of light bulb people may use in their homes. Both types of light bulb produce the same amount of light. Evaluate, in terms of cost and energy efficiency, the use of the two types of light bulb.
Types of light bulb
Energy efficiency
Cost of one light bulb
Average lifetime in hours
Halogen
10%
£1.95
2,000
Light Emitting Diode (LED)
32%
£11.70
36,000

5. Evaluate, in terms of cost and energy efficiency, the use of the two types of light bulb.
So what do you need to do?
Compare the cost in detail. (Use evidence and, if necessary, some calculation.)
Compare the energy efficiency in detail. (Use evidence and, if necessary, some calculation.)
Use these comparisons to support a conclusion – which is best and why.

6. Evaluate, in terms of cost and energy efficiency, the use of the two types of light bulb.
Five minutes to prepare ideas for an answer. Remember to cover ALL that is underlined.

7. Looking at the data: Cost: 1 halogen bulb is cheaper to buy
6 halogen lamps cost the same as one LED
LEDs last longer
Need to buy 18 more halogen lamps to last the same time as one LED
18 halogens cost £35.10
Costs more to run a halogen than LED
LED has lower maintenance cost (where many used, eg large department store lighting)
Energy efficiency:
LED wastes less energy
LEDs are more efficient
LED is 22% more energy efficient
LED requires smaller input (power) for same output (power)
LED produces less heat (applying prior knowledge)
LED works using a smaller current (applying prior knowledge)

8. Which answer is better – and WHY?
The halogen only costs £1.95, which is cheaper than the LED bulb which costs £11.70, but the LED bulb is more efficient and lasts 18 times as long as the halogen does. In the short term, the halogen bulb is cheaper but you would have to buy 18 halogen bulbs in the space of 36,000 hours. Buying 18 halogen bulbs would cost £35.10 whereas you would only need to buy 1 LED bulb in the space of 36,000 hours which is £22.40 cheaper than using halogen bulbs for 36,000 hours.
The halogen light bulb is 22% less energy efficient than the LED light bulb. Moreover, it does not last as long. If halogen bulbs were to run for 36,000 hours – the lifetime of one LED – 18 bulbs would have to be bought altogether. Although one LED, costing £11.70, is more expensive than a single £1.95 halogen bulb, the 18 that would be necessary to make halogen last as long as one LED would cost £ This is £23.30 more expensive. Overall, the LED light bulb is the best because it last 18 times longer, is more efficient and ultimately costs less money. 1 2

9. Which answer is better – and WHY?
The halogen only costs £1.95, which is cheaper than the LED bulb which costs £11.70, but the LED bulb is more efficient and lasts 18 times as long as the halogen does. In the short term, the halogen bulb is cheaper but you would have to buy 18 halogen bulbs in the space of 36,000 hours. Buying 18 halogen bulbs would cost £35.10 whereas you would only need to buy 1 LED bulb in the space of 36,000 hours which is £22.40 cheaper than using halogen bulbs for 36,000 hours.
Unsupported statement about efficiency. If about energy efficiency, need to know how it is more efficient.
Clear analysis of cost in relation to lifetime in hours but waffly and repetitive.
No clear statement of best bulb at the end.
4/6 1

10. Which answer is better – and WHY?
The halogen light bulb is 22% less energy efficient than the LED light bulb. Moreover, it does not last as long. If halogen bulbs were to run for 36,000 hours – the lifetime of one LED – 18 bulbs would have to be bought altogether. Although one LED, costing £11.70, is more expensive than a single £1.95 halogen bulb, the 18 that would be necessary to make halogen last as long as one LED would cost £ This is £23.30 more expensive. Overall, the LED light bulb is the best because it last 18 times longer, is more efficient and ultimately costs less money.
Calculation of efficiency is detailed comparison.
Connectives make comparisons clear and guide reader through reasons for final choice.
Complex sentences allow for management of lots of information at once and aid comparison.
Paragraphing gives parts of answer structure.
Conclusion clearly states which is best. 2
6/6