Alex Reis is a freelance science writer that has written a number of popular articles for The Chemical Blog and other mainstream publications, and has had various scientific manuscripts published in science journals.
Alex contacted ReAgent with a request to buy some chemicals to use for science demonstrations at a Chemistry Day in Acharacle Primary School in Highlands, Scotland. The Chemistry Day took place on 19th March 2015 during Science Week, and it was a chance for pupils to observe and be involved in chemistry demonstrations, so they could enjoy and understand chemical processes.
The aim of the Chemistry Day was to show pupils how chemists can study chemical reactions and understand why they happen. This was done by a series of experiments showing visible changes in chemical reactions using, for example, pH indicators or reactions involving a change of state, such as the production of gas.
Alex has given us a rundown of the experiments she carried out using products supplied by ReAgent.
In this post:
1. Blow Bubbles in Water
One experiment involved blowing bubbles in water. At first, it seemed to the children that nothing happened, but this was just because they couldn’t actually see anything.
A few drops of the pH indicator phenolphthalein was added, and now the children were able to observe that blowing bubbles in water would cause the liquid to go from pink to clear as the carbon dioxide dissolved in water to produce carbonic acid.
Alex added a small amount of bicarbonate soda to the water to make sure it would go pink! The focus of this experiment was to show the clever methods chemists use to detect what happens in a chemical reaction.
2. pH Indicator (Red Cabbage Experiment)
Alex carried out another experiment involving colour changes caused by the different chemicals present. Solutions used here included diluted sulphuric acid, vinegar (acetic acid), water, bleach and sodium hydroxide.
Red cabbage was used to create a purple solution and when this was added to each solution, it would turn a different colour.
Alex gave the children a brief explanation about the difference between acids and bases, with some relatable examples such as orange juice and milk. After the demonstration, the kids tested several liquids from around the school to see what colour they would turn, including juice, washing-up liquid, milk and others.
3. Iodine Clock Reaction
Continuing with the colour change theme, Alex carried out a typical iodine clock reaction. This reaction involves the mixing of two colourless solutions which surprisingly turns brown after a few seconds.
Alex explained to the children about the two different reactions taking place, and how the second can only occur once the first step is completed – which explains the delay in the colour change. This experiment was carried out to show the pupils how chemists sometimes use indirect processes to discover what’s going on during a reaction.
- Potassium iodide
- Sodium thiosulphate
- Starch (such as cornflower starch)
- Distilled water
- Sulphuric acid
- Distilled water
- 3% hydrogen peroxide
All products in these solutions (apart from distilled water and starch) were provided free-of-charge by ReAgent.
4. Changing of State: Baking Soda and Vinegar
Another way to identify what is happening in a chemical reaction is by observing a change of state. Chemicals can go from solid to liquid or gas, and here, Alex used the traditional reaction between vinegar and baking soda to demonstrate the release of gas.
After the demonstration, the pupils tried out this reaction for themselves.
5. Dehydration of Sugar: Production of Solid
Another reaction involving a change of state is the dehydration of sugar with sulphuric acid. For safety reasons, this experiment was performed outdoors as conditions needed to be well-ventilated to keep children away from any fumes.
The experiment is simple; add sulphuric acid to sugar and observe what happens. The sulphuric acid removed water from the sugar in a highly exothermic reaction releasing heat, steam and fumes.
Aside from the sulphur-like odour, the reaction smelled a lot like caramel! The white sugar turned into a black carbonised tube that pushed itself out of the beaker.
6. Different Colour Flames
Another way to identify the chemicals that are present is by the different-coloured flames they produce. This experiment involved lighting chemicals with different coloured flames, including sodium chloride, copper sulphate and potassium chloride.
7. Elephant’s Toothpaste (Use of Catalysts)
Sometimes reactions need a little help – this is where catalysts come in. Under normal circumstances, hydrogen peroxide is decomposed in a very slow fashion, but adding potassium iodide accelerates the reaction.
With a little washing-up liquid, the hydrogen released is captured in bubbles in quite an explosive manner.
The pupils tried out a safer version of this experiment, using a diluted solution of hydrogen peroxide and yeast rather than potassium iodide. However, after seeing the main experiment, lots of the children were slightly disappointed with the safer version!
Final ‘Chemistry Day’ Comments from Alex Reis
“The demonstration ended with a few more examples of chemical reactions and to my surprise, some of the older kids really understood that a reaction involves mixing two (or more) different ingredients to make something new as a result.
“After the demonstrations, the kids had a chance to play with some of the experiments I did. For the younger ones, I also prepared a few extra things such as slime (corn starch and water), moon sand (baby oil and flour) and a lava lamp (water, oil, Alka-Seltzer).
“I believe the kids enjoyed themselves and, considering I was talking to kids from 3 to 12 years old, I think everybody managed to learn something new.”
We enjoy providing chemicals to scientists and schools, especially when they’re used for educational purposes such as the Chemistry Day held at this school in Scotland. If you’d like to purchase our off-the-shelf chemicals for educational or business purposes, you can check out our online chemical store.
Thanks to Alex Reis for providing us with some photos and a rundown of the day.
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