Many students find science skills to be challenging in the usual school lab setting, but learning remotely can make this challenge seem greater.
Getting students to do past practical papers (or parts of these) can be valuable, but this approach alone will not be sufficient for students to develop a deeper understanding of the skills required.
In this post, we will give some examples of how students can access and develop the required practical skills for AS & A Level sciences in a remote learning context.
Some of these activities and examples draw upon ideas from the Collins AS & A Level Student Books, each of which contains Experimental Skills sections for almost every topic which do not require laboratory access.
You can find the sample pages for these resources by clicking on the link here.
When we ask that students carry out any activity, we should keep safety as a top priority. This is more difficult to monitor during remote learning, so teachers should exercise their own judgement about what activities to plan. For example, determining the absolute uncertainty of a volume measured in a kitchen jug would be acceptable, but using boiling water to make solutions in kitchen glassware may not. Risk assessments should be part of any experimental plan.
Always encourage students to write their own risk assessment. The minimum should be ‘This is a low-risk activity with no specific hazards. The usual laboratory rules should be followed.’ Beyond that, any safety precaution should be specific to the procedure. For example, ‘Oxygen gas will be evolved, so oxidisable materials should be removed and flames should not be used.’
When questioned, students at AS & A Level usually say that planning is one of the easier skills, yet many do not access full marks when assessed. Independent, dependent and control variables should be identified in practice scenarios, along with a workable method being given.
Points that students often miss are:
- Those which will ensure accuracy or reproducibility of the results. For example, ‘Rub the ends of the wire lightly with sandpaper to ensure a good electrical connection to the crocodile clips.’ or ‘Use a thermostatically controlled water bath to ensure that the temperature remains constant.’
- Justifying what equipment to use, such as ‘Use a 500 cm3 measuring cylinder to collect the gas because my calculations show that the volume evolved will to too great for a standard 100 cm3 gas syringe.’
- Justifying procedures, like ‘Observe the cells using a magnification of x500 and count the chromosomes in a cell at metaphase or anaphase.’
- Methods of analysis, such as ‘If the predicted relationship between the time period and the length is correct, then a graph of T2 against l will be a straight line through the origin.’ or ‘A minimum of three readings should be made for each plant species and the means should be compared.
Ask students to write a whole plan for an investigation and provide them with success criteria in advance. The success criteria can be in the form of a check-list. For example, ‘I have identified both dependent and independent variables and stated how these are to be measured’ etc. Use past papers and the Collins AS & A Level Student Books for ideas. After identifying which areas need development with each student, focus on these with more detailed success criteria.
#3: Making measurements and recording results
Teachers and students often think that these skills cannot be practised at home. Obviously, at home, we do not have access to more sophisticated equipment, but this is a good opportunity to deconstruct the misconception that science only happens in a lab. There are many examples of investigations that can actually be carried out at home. Each of these can be developed with further questions.
- Collecting leaves from two different heights, such as 0.5 m and 1.5 m on a woody plant and comparing their surface areas. A plant that is non-toxic to the touch and that contains no known allergens should be chosen. Students can be given a plan or can plan their own investigation, then carry it out. How can the surface area of a leaf be determined at home? Plan and detailed drawings can be made from light micrographs that are found on science photography websites.
- Placing clean iron nails into water with various concentrations of table salt, then removing the nails to air-dry. The time taken to rust or the percentage cover of rust could be compared. What units of concentration should be used at home when sensitive weighing apparatus (to enable a moles calculation) is not available? If lab access was possible, how could the mass of rust on each nail be determined? What would be the advantage of converting this to a percentage mass?
- A simple oscillating system such as a home-made pendulum or weighted plastic ruler held horizontally off the end of a desk can be set up. The stopwatch app on a smartphone can be used to measure the time period when a key variable is changed. What unit could be used to measure the load on the ruler without access to a sensitive balance? Would a time index on a phone’s video with a resolution of 0.01 s remove the need to take repeat measurements and calculate a mean?
Many websites have quite sophisticated simulation software that enable results to be recorded from a wide range of experiments. Use a search engine to look for ‘<type of experiment> simulation’ and explore some of the hits. Students can then be given the direct link to the chosen simulation.
Learners without access to any resources at home can be allocated into groups to work remotely with others. For example, one student with a video camera can show the oscillating system to the others who use the time index on their own video to determine the time period. One student can share photographs of their leaves sitting on squared paper, etc.
#4: Analysis of results
Students can quite easily be given sets of data to analyse at home. By the time students get to AS & A Level, graph plotting should be already well practised, but often scaling axes and use of error bars can still be a challenge. Ensure students have access to 2 mm square graph paper and devise ranges of results that will make a suitable scale progressively more challenging.
Giving a set of results for an exponential decay, such as counts per second from a radioactive sample or the current from a discharging capacitor can be a useful way of students practising how to use natural logarithms to enable a straight line to be plotted.
Similarly, the cell potential of an electrochemical cell has a straight-line relationship with the log10 concentration of the aqueous ion.
Such graphs also involve the use of negative numbers, which can be challenging for some students.
Results of population genetics studies can be provided for students to apply, for example, chi-squared analyses. In these cases, students should be provided with any statistical tables and equations.
Teachers can use software such as Excel to generate their own data sets for students to plot. By using the trendline option, a line of best fit can be seen in advance. Points can then be manually adjusted to be just off this line to add challenge to the students when drawing their own line of best fit. Some of these apps also allow the equation of the trendline to be shown so the ‘ideal’ gradient or intercept is known by the teacher in advance.
This is possibly the most challenging of all practical skills, partly because many students do not completely understand what is required. For example, many students consider it sufficient to refer to better equipment, or using meters with digital rather than analogue displays.
Fortunately, evaluation is one of the skills that lends itself well to remote learning.
Practising this skill can be done in two ways:
- Identifying limitations/sources of error or uncertainty and suggesting improvements. For example, when determining an enthalpy change in a glass beaker and using a thermometer with a resolution of 1 oC improvements could be using a polystyrene cup with a lid and a thermometer with a resolution of 0.5 oC as these changes would reduce heat loss to the surroundings and reduce the percentage error in the results respectively. Students find this to be a difficult skill and may need support with this initially.
- Recognising absolute or actual errors or uncertainties. Students can do this at home using domestic measuring equipment. For example, the absolute or actual uncertainty of bathroom weighing scales with a resolution of 1 kg can be quoted as ± 0.5 kg or 1.0 kg. They can then calculate the percentage uncertainty in the mass, for example, of a suitcase. This can be extended to derived values. For example, if the uncertainty in a value of T is 0.1 s, then what is the uncertainty in T2? These uncertainties can then be shown as error bars on graphs so best and worst fit lines can be drawn and uncertainties in gradients determined.
Provide students with an experimental procedure and a writing frame or cloze (gap-fill) passage to support them in recognizing sources of error and suggesting improvements.
There are many video resources that show how to calculate errors or apply error bars to graphs. Go to an online video resource and search, for example, for ‘error bars AS & A Level physics’ and explore the hits. Don’t forget to watch the videos before providing direct links to ensure their suitability and accuracy!
- Start with a skills area where you feel most confident.
- Always develop a clear set of success criteria for each task and share these with students in advance.
- Provide support, or scaffolding, when starting something new. Remember, it is better to provide too much support than too little!
- Allow students to work in remote groups and share ideas when working on a task. Perhaps the first task in each skill area could be a collaborative group effort.
- Set clear targets for when and how you want work to be submitted.
- Once students clearly understand the criteria for each skill area, then peer-assessment can be used. This can be accompanied by them giving each other feedback.
Michael Smyth graduated with a PhD in Biophysics and began his career in research at the University of Oxford. His work has been featured in major newspapers and he has won international awards for his work in science education. A senior examiner for over 20 years, Michael currently writes and marks exam papers, trains teachers and examiners and writes books and articles on science. Including the Cambridge International AS & A Level Biology, Physics and Chemistry resources.