Thursday, 29 May 2014

Colourful Ooohs and Aaahs

Chemistry is one of those subjects that conjures up the image of a mad scientist playing with wonderfully coloured potions, aided by much fire, smoke, and explosions.  Well, at least that was what I had thought of the subject as a child!  In my school days (that was a very long time ago), we were not allowed to learn chemistry in school until 15 years old, and only to prepare for the O-level exam.  I waited in excited anticipation to start studying my dream subject only to drop it promptly after two lessons when my then-chemistry teacher insisted upon having us memorise the entire periodic table which she would then test us on our memorisation skills in the third lesson before we were deemed "good enough" to conduct any chemistry experiment!  That killed my interest for the subject on the spot.

Tiger's experience with chemistry has, thankfully, been very different.  We approach it in as much a hands-on way as possible.  At this stage, I seek to maintain a healthy level of interest and a sense of curiosity in Tiger rather than to require him to memorise information.  There may come a time when he needs to memorise the periodic table, but not just yet.

In the past six weeks we have been busy following the Kitchen Chemistry course offered by FutureLearn.  Lucinda has written an informative piece about their experience with the same course so I won't repeat the information but I will share some highlights of our experiments from the course.

One of the early experiments to demonstrate rising hot air called for a special kind of teabag that I couldn't find from the supermarkets but we carried on with the experiment using our normal teabag.  Alas, it didn't work.

video

Next, we explored the concepts of states of matter via physical and chemical changes.  I shall expand more upon the candle experiment (see Lucinda's post for more details on this topic) in a later post.  What I will show you is the standard bicarbonate soda reacting with vinegar video, which is a stanard 'erupting volcano' experiment that many children are familiar with.  One can't go wrong with this experiment!

video

In the third week we learnt about solubility.  The standard oil-in-water experiment was part of that week's set of experiments.


We found the experiment to separate soluble substances to be particularly interesting, no less because we got to play with the iodine solution, which has become a rare item in the UK since 2009 due to an EU 'recommendation'.


What's facinating in the above experiment is that iodine actually dissolves better in oil, as shown in the righthand-side photo.  If you look closely at the video clip below, you can see the liquids separating:

video

Tiger then became curious about the density of water versus that of oil, so he dropped a few drops of water using the pipette into the mixture and saw how the water droplets travelled through the oil-and-iodine mixture (at the top) to the water (at the bottom).

video

Chromatography is an extension of the solubility test.  We did separate experiments using felt-tip pens and food colourings, and found that we had better results with the felt-tip pens.  It may be due to the quality of the food colourings we have.  Nonetheless, the process of chromatography is always very colourful and somewhat magical.


Next, we made red cabbage indicator to test for acids and alkalis using various household items: lemon juice, washing up liquid, table salt, washing soda, toothpaste, and vinegar.


Out of all the items we tested, the most visible change in colour came from the washing soda (sodium carbonate), which is an alkali and therefore turned the red cabbage indicator from light red into a dark green colour almost immediately.

video

As we boiled a whole red cabbage, we had a large quantity of red cabbage indicator at our disposal so we continued with the acid/alkali experiment using milk of magnesia (an alkali) and vinegar (an acid) to play around with the different levels of pH.


When the indicator was added to the milk of magnesia, the solution turned green, indicating its alkalinity.

video

When vinegar was added to the solution, the solution turned pink, indicating its acidity.

video

We also used iodine to test for starch (cornflour mixture).


Using two iodine solutions (one bottle is the control), we added the starch solution to one of them.  The change in colour was immediate, indicating a presence of starch.

video

The course has given us a reason to take an interest in chemistry again so we will be spending a few more weeks exploring it.


This post is linked up to:
  1. Hip Homeschool Hop - 5/27/14
  2. The Homeschool Mother's Journal (5/24/14)
  3. Science Sunday - 10 June Science Ideas for Kids
  4. Weekly Wrap-up: The First Week of Summer Break 2014

11 comments:

  1. Hwee,

    I had a look at the FutureLearn website. What a great way to learn! I also like Lucinda's science posts.

    I studied biochemistry at university and the chromatography experiment brings back memories! So far none of my children have shown any interest in performing experiments but they do like chemistry. They love the videos on the Periodic Video site. Charlotte watched each one 2 or 3 times. Chemistry is such a fascinating subject and it is everywhere in our lives!

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    1. The MOOC courses are good for learning at home when the child is ready. The Kitchen Chemistry course happens to be pitched at an introductory level so many homeschoolers I know took it with their children.

      We do science in a number of ways, watching videos is one but Tiger learns more by engaging his hands at the same time. I've read your posts about how Charlotte learnt chemistry, and have been inspired by her process. I'm saving the Period Videos for later when we learn about the elements. Thank you for the tip! :-)

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  2. I had read about the Kitchen Chemistry but didn't sign up as there was too much going on at the time. That was probably a mistake! We made red cabbage indicator recently which was a great success.

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    1. The course may be repeated in the future, as they often do with MOOCs, so keep an eye out for it! :-) The red cabbage indicator is such a useful tool for chemistry lessons. I don't know why I didn't do it earlier.

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  3. What a great course! We have tried the chromatography experiment on a few occasions but have never been successful, I'm not sure why. It looks like all your experiments worked which I think goes a long way to extending one's enthusiasm for more! What will you try next?
    Are the periodic videos on Sue's blog, do you know? If not would you be able to tell me what they are called?
    Have a lovely weekend Hwee!

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    1. Have you tried using different types of absorbent paper for your chromatography experiment? We used coffee filter paper and blotting paper. Not sure what we'll do next yet, since the course has to be pitched at the right level for Tiger to benefit from it.

      The periodic videos are made by Nottingham University, that covers all the elements of the periodic table. They can be found here: http://www.periodicvideos.com/


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  4. The liquids separating was a cool video. Now I'm itching to do some chemistry and play around with red cabbage. I'd actually bought some for expressly that purpose and then we got distracted and the kids accidentally put the cabbage in the back of the pantry and needless to say when I found it, it was not going to be used for anything.

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    1. That's a funny story, Ticia! :-) I have had similar experiences many times over with different perishable items that just got pushed to the back of the cupboard until weeks later when they've turned into disgusting items. :-)

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  5. Hwee, this is wonderful! I love all your photos and videos of the fun experiments you've been doing. We haven't got further than the chromatography week. Our saline chromatography didn't work nearly as well as yours, but we did do a fun extension. We noticed that Sharpie permanent markers didn't dissolve at all in water, so we used alcohol instead. We made very cool tie-dye effect designs on white cotton. It was a great demonstration of how some substances don't dissolve in water but do dissolve in other liquids. The experiment is on Steve Spangler.
    (I need to re-subscribe to your blog - I didn't get an email again. Over-active spam filter, perhaps.)

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    1. I saw the same experiment on Steve Spangler and thought it would be a really cool extension but didn't get round to doing it. I'm glad you did and have shared your findings here.

      I think our chromatography experiment went so well because the felt-tip pens we used are the really cheap ones with highly soluble ink. :-)

      The Blogger site has been acting rather strangely last week so I wonder whether that has messed up the subscriptions... sorry about that, Lucinda. I hope it is fixed now.

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  6. Wow! I love all the cool experiments with chemistry, Hwee. I'm going to have to remember the Future Learn website as my children get just a touch bigger :-)

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