experiments

Fun (and very effective) revision activity

Here’s an oldie but a goodie (I first did this as a Fifth Year student in Tarbert Comprehensive on a religious retreat back in Ballyheigue. It’s also all I remember from the retreat). It is an exercise in communication but acts as both an excellent revision activity and ticks the verbal literacy box. And it’s a lot of fun.

I did it with my Leaving Cert Physics class because I have them last class on Friday (and Jacqui finds it hard to concentrate). So a challenge I have now set for myself is to find a fun learning activity for them every Friday between now and May.

photo(1)
Students pair up in twos (I love saying that, just to annoy the pedants). They can pair up in threes if there’s one left over.
Students sit back to back.

There are 24 mandatory leaving cert experiments. The first student (student 1) picks an experiment (or is assigned one) and, with his (or her) back to student 2, proceeds to instruct on how to draw the experimental apparatus. But here’s the kick: student 1 can only instruct student 2 one line at a time, e.g. “Start at the top of the page and draw a line parallel to the top half-way across. Now draw a line down three quarters of the page”. Student 1 cannot however tell student 2 to draw a power supply; student 2 has to figure this out from the instructions. Obviously student 2 doesn’t know what the experiment is and the aim is for him or her to figure this out in the shortest time possible. Neither can student 2 communicate with student 1 in any way; he just has to follow instructions as best he can. At the same time student 1 can’t look over her shoulder to see how the diagram is progressing.

Once identified, student 2 then gets a turn at calling out the instructions for another experiment which student 1 has to draw and try to identify in a shorter time.
Alternatively have all pairs doing doing the same experiment and see which pair can identify the experiment first.

So yes it’s great fun, and yes it really demands a high level of verbal and spatial reasoning, but the reason I really like it is because it involves active learning; student 2 is mentally retrieving all the experiments to see which one best matches the diagram. And this has been shown, time and time again, to be one of the most effective ways to learn.

You could spend five minutes on this at the beginning of every lesson. There’s also no reason why this can’t be rolled out for Junior Cert Science students.

Another nice aspect to it is that there is no preparation on the teacher’s part; no photocopying, correcting or cleaning up afterwards.

Finally, we use mini-whiteboards (also known as “Show Me” boards) in class – they are perfect for this activity.

Imagine if we all shared our own one favorite fail-safe activity?

Advertisements

How to get 100% in your Leaving Cert Physics exam. Part 2: Answering Graph Questions

The following can be downloaded as a word document here

Drawing the graph

  • You must use graph paper and fill at least THREE QUARTERS OF THE PAGE.
  • Use a scale which is easy to work with i.e. the major grid lines should correspond to natural divisions of the overall range.
  • LABEL THE AXES with the quantity being plotted, including their units.
  • Use a sharp pencil and mark each point with a dot, surrounded by a small circle (to indicate that the point is a data point as opposed to a smudge on the page.
  • Generally all the points will not be in perfect line – this is okay and does not mean that you should cheat by putting them all on the line. Examiners will be looking to see if you can draw a best-fit line – you can usually make life easier for yourself by putting one end at the origin. The idea of the best-fit line is to imagine that there is a perfect relationship between the variables which should theoretically give a perfect straight line. Your job is to guess where this line would be based on the available points you have plotted.
  • Buy a TRANSPARENT RULER to enable you to see the points underneath the ruler when drawing the best-fit line.
  • DO NOT JOIN THE DOTS if a straight line graph is what is expected. Make sure that you know in advance which graphs will be curves.
  • BE VERY CAREFUL drawing a line if your ruler is too short to allow it all to be drawn at once. Nothing shouts INCOMPETENCE more than two lines which don’t quite match.
  • Note that examiners are obliged to check that each pint is correctly plotted, and you will lose marks if more than or two points are even slightly off.
  • When calculating the slope choose two points that are far apart; usually the origin is a handy point to pick (but only if the line goes through it).
  • When calculating the slope DO NOT TAKE DATA POINTS FROM THE TABLE of data supplied (no matter how tempting!) UNLESS the point also happens to be on the line. If you do this you will lose beaucoup de marks and can kiss goodbye any chance of an A grade.

 

 

What goes on what axis?

Option one

To show one variable is proportional to another, the convention is to put the independent variable on the x–axis, and the dependant variable on the y-axis, (from y = fn (x), meaning y is a function of x). The independent variable is the one which you control.

 

Option two

If the slope of the graph needs to be calculated then we use a difference approach, one which often contradicts option one, but which nevertheless must take precedence. In this case we compare a formula (the one which connects the two variables in question) to the basic equation for a line: y = mx.

See if you can work out what goes on what axis for each of the following examples (they get progressively trickier):

  1. To Show Force is proportional to Acceleration
  2. Ohm’s Law
  3. Snell’s Law
  4. Acceleration due to gravity by the method of free-fall
  5. Acceleration due to gravity using a Pendulum

 

There is usually a follow-up question like the following;

“Draw a suitable graph on graph paper and explain how this verifies Snell’s Law”.

There is a standard response to this;

“The graph of Sin i against Sin r resulted in a straight line through the origin (allowing for experimental error), showing Sin i is directly proportional to Sin r, and therefore verifying Snell’s Law”.

 

If you are asked any questions to do with the information in the table, you are probably being asked to first find the slope of the graph, and use this to find the relevant information.

 

 

How to get 100% in your Leaving Cert Physics exam. Part 1: Section A

Section A counts for 30% of your overall mark and is the easiest section to pick up full marks. There are about 24 experiments but many of them are minor variations on each other. Stop wasting time trying to predict which ones will come up and just learn them all. Take one or two per night and make sure you can answer every question on each experiment from past papers. In particular you need to use the following as a checklist for each experiment.

(i)     Draw a fully labelled diagram which includes all essential apparatus (have you included the apparatus necessary to obtain values for both variables?).

(ii)   Be able to state how the two sets of values were obtained (this is a very common question).

(iii) Describe what needs to be adjusted to give a new set of data

(iv) Write down the relevant equation if there is one associated with the experiment.

(v)   Be able to state how the data in the table will need to be adjusted.

(vi) Know what goes on each axis.

(vii)           Know how to use the slope of the graph to obtain the desired answer.

(viii)         Be able to list three sources of error/precautions.

Misc Points

  • The graph question is usually well worth doing.
  • Learn the following line off by heart as the most common source of error: “parallax error associated with using a metre stick to measure length / using a voltmeter to measure volts etc”.
  • Make sure you understand the concept of percentage error; it’s the reason we try to ensure that what we’re measuring is as large as possible.
  • There is a subtle difference between a precaution and a source of error – know the distinction.
  • When asked for a precaution do not suggest something which would result in giving no result, e.g. “Make sure the power-supply is turned on” (a precaution is something which could throw out the results rather than something which negates the whole experiment).
  • To verify Joule’s Law does not involve a Joulemeter
  • To verify the Conservation of Momentum – the second trolley must be at rest.
  • To verify the laws of equilibrium – the phrase ‘spring balance’ is not acceptable for ‘newton-metre’.
  • To measure the Focal length of a Concave Mirror or a Convex Lens.
    Note that when given the data for various values of u and v, you must calculate a value for f in each case, and only then find an average. (As opposed to averaging the u’s and the v’s and then just using the formula once to calculate f). Apparently the relevant phrase is “an average of an average is not an average”.

I have a document here which containts exam questions on every experiment which has ever appeared on a past paper from 2002 to 2010 (Higher Level and Ordinary Level) – this should be your bible for Section A over the coming weeks. Solutions are also included.

Now get back to work.

More to come.

Junior Cert Science revision: the experiments

 
With the Junior Cert Science exam just around the corner this resource will come too late for most, but for what it’s worth I am highlighting it here anyway. With over 45 experiments needing to be written up for Coursework A the sheer volume can be quite intimidating, particularly for those of us who are struggling with the subject in the first place.

That’s why I’ve put together a very short summary of all the experiments on the revision page of thephysicsteacher. Each set (Physics, Chemistry and Biology) can fit onto one double-sided page (well almost – need to work on reducting Physics) and if students are looking for a more indepth description they can go to the original notes, which also contain every question which has ever appeared on an exam paper (at Higher and Ordinary level) along the accompanying solutions.

Hope it’s of use to some of you out there.

And remember – real Science bears little or no resemblance to the rubbish you have to learn for this exam, so try not to be put off by the subject.

Teaching Heat in Junior Cert Science

There are a large amount of experiments in this chapter:

  1. Expansion and contraction of solids.
  2. Expansion and contraction of liquids.
  3. Expansion and contraction of gases.
  4. Water is a bad conductor.
  5. Expansion of water on freezing.
  6. Comparison of conduction in various metals.
  7. Convection in liquids.
  8. Convection in gas.
  9. Compare radiation in bright and dark surfaces.
  10. Plotting cooling curves.

This can lead to problems on two fronts:

  1. It can take an inordinate amount of time to get through the chapter.
  2. Students can easily get confused about which experiment goes with which concept.

It makes sense to group experiments into sections, and if possible carry out each set of experiments together.
This does however take a little organisation in advance.
So here we look at the expansion of solids, liquids and gases; the aim is for the students to get through all three in one period, although they would need to be prepared in advance.
Allow a double-class if trying this for the first time, for obvious reasons.
It’s never going to make the best of youtube, but hopefully it will help the teachers in my own science department. I hope to get through the rest soon, and then summarise as best I can on one page using diagrams.

Thanks to my second-year class of  for being amazingly patient.
And thanks to Millie for the brilliant camera-work (can you believe she had never used a camcorder before?!)

Colleagues: Please ensure that the equipment goes back into the correct boxes after.
Pretty please?
With a cherry on top??

Late update: I’ve just seen Tom Healy’s videos of the same expts on youtube, but put together much more lovingly. I reckon they all complement each other nicely!

Do you hate correcting experiment-copies as much as me?

Because I hate it. I mean really, really hate it. So much so that I haven’t corrected a (leaving-cert) copy in years. I justify this (to myself) on the basis that I spend more than enough time in the lab on technician duty. I’m generally in the lab by 7:15 and spend most breaks there also. It may be putting together apparatus for some experiment or trouble-shooting gammy equipment which was returned broken by a student (or teacher).
Anyway, point is, I don’t apologise for taking shortcuts when I can.

So here’s what I do.
I have put together a marking scheme for every Leaving Cert mandatory experiment report and get the students to correct each others’ reports based on this marking scheme. They can’t keep using the same student to correct their report, and their final mark for each report must be entered in a master sheet which I keep open on the front desk. They can argue with each other as much as they like over their marks – but each mark must be justified.

What’s more, I give this marking scheme to the students at the beginning of the year so they get to use this to help them write up the report as they go along.

Students tape or paste the appropriate marking scheme on to the same page as the experiment it refers to.

At the very least I want them to appreciate that it doesn’t matter how much they write; there is always some key information which must be included.

  1. A labelled diagram including all essential apparatus (paying particular attention to how results are to be obtained).
  2. A description of how values were obtained for each variable.
  3. An explanation of what was changed to enable obtaining other sets of data.
  4. How the results were manipulated to allow for interpretation.
  5. Graphs, conclusion, sources of error etc.

I usually need to remind them that a report without results gets zero marks, because it’s not a report. it’s like a journalist giving a report of a match without including the result – pointless.

Every so often, after first forewarning the troops, I inspect their copies to ensure that they are actually writing up the reports. But they must have their copy open at the correct page – because I refuse to take up their copies. I also tell them that copies are to he handed up for inspection before each end-of-term report and are worth 10 % of final mark. This is a lie. I refuse to take up their copies (although when volunteer them I do store them for the students – I’m nice like that).

The irony is that this approach seems to tie in nicely with what the educationalists tell us is ‘Formative Assessment’ and encourages the student to take responsibility for their own learning.
Which is obviously why I do it. Ahem.

Formative Assessment – wikipedia

Assessment for Learning (AfL) – my webpage

Experiment copy marking scheme here

Hope they’re useful 🙂

Update.
We had an inspection in (I think) 2010 and the inspector commented favorably on this method of student learning.
Which is obviously why I do it.

By the way, if printing these for your class make sure you use the ‘print two pages onto 1’ option to reduce photocopying and paper costs.