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Sorry for not posting anything these last few weeks. Have been doing other things recently, not given much time to Chemistry recently until a couple of days ago when class 10 returned.

When you come to school, please bring with you the work you have done during the vacation. I’d like to go through it. Looking forward to meeting you all soon. 🙂

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I’ll be away on the Himalayan trek from May 2nd to 13th. I’ll not be able to attend to any queries during this duration. In the meantime, do try out some of the things I’ve been posting about.

Kitchen Chemistry

Have you realised that each of you have a chemistry lab inside your own house? Yes, the kitchen. Have you ever wondered what happens when rice is steamed, or potatoes are fried, or cakes are baked?

http://www.rsc.org/Education/Teachers/Resources/kitchenchemistry/resources4_2.htm

Kitchen Chemistry is a collection of information about various experiments to study the chemistry of food and cooking, put together by the Royal Society of Chemistry. There are also some video clips available for some of the experiments. Not all experiments can be done at home with common materials, and some of them involve some advanced chemistry, but still you could take a look at it and see if you can figure them out.

Here’s something for those of you who would like to do something with what you can find lying around in your house.

Try making saturated solutions of common salt and sugar in water. A saturated solution is one in which you cannot dissolve any more of the solid, at that temperature. To prepare a saturated solution of salt in water, take a cup of water, keep adding one or two spoonfuls of salt at a time, keep stirring and adding more salt when it completely dissolves. You will reach a point when some salt is left undissolved at the bottom, no matter how much you stir. Then it is saturated.

You can try various things with the saturated solution and observe what happens.

  • Drain off the clear solution into a second cup, leaving behind the undissolved salt/sugar in the first cup. Leave the solution to evaporate for a couple of days and see what happens. You could try using different kinds of vessels to do the evaporation- wide, shallow saucers, or deep bowls- and see whether it makes a difference.
  • Try freezing the solutions by keeping inside the refrigerator.
  • Try heating the solutions to evaporate the water.

CAUTION: ANY HEATING SHOULD BE DONE WITH THE HELP/UNDER THE SUPERVISION OF PARENTS.

Here is your first worksheet for the vacation(which all of you have to complete)! It is a tutorial cum worksheet on chemical equations, borrowed from the website of David Katz, an eminent Chemistry educator, who has been kind enough to share so many of the resources he has compiled himself, on his website http://chymist.com .

http://chymist.com/Equations.pdf

The worksheet begins with a review of what information chemical equations convey, the reasoning behind balancing chemical equations etc. This is followed by many problems on balancing equations.

Then it covers different kinds of chemical reactions- direct combination, decomposition etc. It then gives a set of problems in which you are asked to predict and complete chemical equations, by identifying the type of reaction that could occur between the given reactants.

You can never be absolutely sure about a prediction regarding a reaction unless you actually carry it out in the lab. But it is valuable from the point of view of exams, to develop the skill to be able to relate a set of reactants which you have not encountered, with reactions that you are familiar with and make intelligent guesses as to what reaction might occur. So please attempt to complete all the reactions given at the end of the worksheet. It’s alright if you get it wrong. We could even try out some of those reactions in the lab when you come to school in June, and verify the predictions.

This is a book you must read, if you have become interested ever so slightly in the fascinating history of Chemistry, after watching the BBC documentary. Oliver Sacks is a famous neurologist, but this book is about his childhood, when he was deeply and enthusiastically into amateur Chemistry, due to the inspirational influence of his uncle who owned a bulb factory, and used to talk to him always about the qualities of tungsten as the perfect metal for use in bulb filaments. The book is in a way, his personal account of the history of Chemistry and his own journey in understanding Chemistry. It also gives you a glimpse into the life of a Jewish family in England during the second world war. The book is written very lucidly, and it is a popular science book, so you would be able to digest and understand it quite easily.

If you are interested, you can get your parents to order it online, on Flipkart: http://www.flipkart.com/uncle-tungsten-oliver-sacks-book-0330390287?ref=a2d135b3-bae6-4e95-bd9b-604f1aea1317

Causes of Colour

Continuing with our preoccupation with light, colours and spectra, perhaps it might be a good thing to learn a bit more about light.

Causes of Colour will help you understand more about why our world is so colourful. It is an online presentation which covers the basic aspects of the production of light, the absorption of light by different objects, our eyes and how we perceive light etc. It may be more of Physics than Chemistry, but sometimes the two overlap so much that it’s better to forget about classifications. It is closely linked with Chemistry because the colours of different objects can be ultimately explained by the molecular and atomic structures of substances which determine which colours of light they absorb/emit.

I’d recommend you to go through this website in detail, step-by-step. It explains so much about light in simple terms.

P.S. By the way, I expect everyone is caught up with the cricket fever right now(What a match it was yesterday!). I can see that though many of you have visited the blog, only one or two of you have actually tried exploring the spectroscope. I hope more of you will try it out yourselves, once the world cup is over, and you’re left jobless(!).

Building a CD Spectroscope

I can see from the site visits statistics that many of you have logged in to see whether I’ve posted anything! Sorry if I have been late in putting up something for you to do. We can probably start with building the pocket CD spectroscope.

Before you start, let us recall what spectroscopy means. Remember, a spectroscope splits light into its component colours. Light from different sources made of different materials give different spectral patterns, and studying the patterns can reveal the materials present in the light source.

There are several designs which you can use to make your own spectroscope, but I would recommend this one which I have tried out myself. http://www.amnh.org/resources/rfl/pdf/du_u03_spectroscope.pdf You just need to print out the template on a piece of paper, paste it on a piece of cardboard and follow all the instructions closely. You can also use the design on Arvind Gupta’s toys website- http://www.arvindguptatoys.com/toys/cdspectroscope.html

You can choose either of these designs. Try to read through the instructions and see if you can figure it out yourselves. If you have any questions regarding the construction of the spectroscope, please feel free to post them as comments. I’ll respond to them as soon as I can. All you need is some paper, cardboard, glue and a piece of an old CD!

Once you have made the spectroscope, you can try pointing it at different light sources and study the different spectral patterns that are revealed. Most of you have already seen the spectrum produced by tube light, which closely matches with the spectrum of mercury. You can also try studying the light emitted by CFLs(Compact flourescent lamps- those small white energy-efficient lights), your computer screen, a candle, LED flashlights etc. DO NOT LOOK AT THE SUN DIRECTLY- IT COULD DAMAGE YOUR EYES.

If you are interested in knowing a bit more about spectroscopy you could look at these websites-
http://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html
http://www.amateurspectroscopy.com

P.S. The width of the slit which lets light into the spectroscope is crucial. If it is too small, it will not let in enough light and you will not see anything. If it is too wide, it will let in too much light and you will not see a clear, sharp spectrum. Experiment by varying the width of the slit and see if you can find out the optimum width for your spectroscope. Also see if you can modify the design so that you can vary the width as and when you wish!

Hello!

Dear students,

I am hoping to make use of this blog to keep in touch with you and help you keep in touch with Chemistry during the long summer vacation. I will be posting interesting articles for you to read, projects for those who are interested in doing something hands on and yes, a few worksheets which you all have to complete.

An advantage of using a blog is that you can put comments under a post, if you have a question or you want to respond- and I can again post comments in response to that. I hope to be able to put up something for you to read/do regularly. Please keep visiting the blog often to see if there is anything new.