'What we did' on Friday 11th March 2011Our main subject matter for the evening was a touch of CHEMISTRY & PHYSICS.
OPENING DEMONSTRATION EXPERIMENT - 'Experiments with Dry Ice'.
We had about 15 blocks of dry ice. Dry Ice is compressed and frozen carbon dioxide. At normal air pressure dry ice sublimes at -78C. At that temperature it turns from solid directly into a gas without going through any liquid state.
We placed pieces of dry ice in a glass bowl and added warm water. Great! The gas (looked like steam) floated downwards on top of the table and down to the floor. We then added concentrated detergent and food colouring and watched the dramatic results.
The dry ice was handled very carefully using 'heat/cold resistant gloves'.
INTERACTIVE SOUND 1 - Amongst equipment that has been donated to the club is a 'Sound Level Meter' measuring sound in decibels. We used the instrument to measure the level or loudness of sound made by children talking quietly and loudly.
INTERACTIVE SOUND 2 - We talked about 'high' and 'low' sounds and learnt the word 'frequencies' to describe high notes and low notes. We blew up some balloons and inside each balloon inserted a 'hex nut'. By swirling the balloon around fast the hex nut produces a screaming sound. We held this over a microphone and amplified the sound and discovered that as the hex nut slows down the frequency of the sound becomes lower.
INTERACTIVE SOUND 3 - We learnt how to recognise sounds. We used our sound system to play a number of short sound bites and the children had to guess what they were.
INTERACTIVE - ACIDS & ALKALIS - and the 'pH' scale Acids and alkalkis are substances that produce reactions when mixed with other substances, such as water. They can both be either weak or strong. Acids and alkalis cancel out, or neutralise each other when mixed together. The strengths of acids and alkalis are measured on the pH scale.
Every child contributed to the experiment by making a pH Indicator to test whether a subtsance was an acid or an alkalki.
We cut some RED CABBAGE into very small pieces then squashed the pieces in a bowl of water until the water became purple. All the liquid was then poured and filtered into a large jug.
Each child then had a glass with some of the indicator liquid. Various liquids were added and found that if it was an acid ie a citrus fruit the liquid changed to a reddish colour. If it was an alkali ie bicarbonate of soda it changed to a blueish colour. We could even change the colour back again.
How to remember...pH scale 1 to 14 with 7 - neutral
1 to 6 - 'low' numbers' = red - short word = acid short word.
8 to 14 - 'high numbers' = blue - long word = alkali - long word.
INTERACTIVE - ULTRA VIOLET LIGHT We discovered how different materials, some which we were wearing and different liquids reacted to UV light. One child came and dipped their fingers into a jar or Petroleum Jelly and found that part of the ingredients reacted to the UV light. We had 3 jars of UV reactive liquid produced from fibre of highlight pens.
The March issue of 'making science cool' booklet was handed out
- click here to see pdf copy or if children absent the booklet was posted.
In all a fantastic evening for children and helpers
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