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In this experiment we take a closer look at flames and burning and discover what flames are made of and why candles are actually quite clever devices.
The fuels used by a candle and the fuel used by a cooker are chemically very similar. However - the flames are usually very different. Can you explain ?
INVOLVES BURNING CANDLES and Molten WAX!
You will need:
- Transparent plastic tray ( eg sandwich box) 20 x 10 x 3cm minimum
- 1 x tealight or large white candle
- 2 x Birthday candles + holders
- 2 x clean jam jars - taller the better
- 1 x small potato whose diameter is about half that of the jam jar
- Clean drinking straw or similar tube (to be breathed through)
- Knife to cut potato in half
- A few drops of washing up liquid
What we did..
- Cut the potato in half along its length .
- Place one of the halves flat face down in the centre of the plastic tray
- Stick the birthday candle into the potato
- Pour water into the tray to just cover the potato
- Light the candle and observe the flame
- Slowly and carefully - with a hand either side, bring the jam jar slightly over the burning candle. Observe the flame and the inside of the jam jar
- When you can see no more changes, slowly lower the jam jar a little more. CAUTION IT WILL GET HOT.
- As it gets hotter, lower the jam jar right down into the water and observe again. watch the level of the water in the jam jar especially carefully. Observe, describe, explain
What we found out..
- condensation collected on the inside of the jam jar
- a black coating formed on the inside of the jam jar
- the jam jar got hot !
- when the jam jar was placed completely over the candle , the flame went out after a few seconds
- after the flame went out the water level inside the jam jar appeared to rise
The tekkie bit..
A candle is a clever device, designed to keep burning continuously until its fuel ( wax) is used up. Wax is a hydrocarbon.When hydrocarbons burn in the oxygen of the air , the carbon in the hydrocarbon (wax) joins with the oxygen to form mostly carbon dioxide (CO2) and the hydrogen joins with the oxygen to form water ( H2O) . This water is what formed the condensation on the inside of the jam jar.
The flame produced by the candle is a mixture of hot gases ( carbon dioxide, water vapour and carbon monoxide) . Some of the carbon in the wax does not get burnt and remains as carbon and is what formed the black ( sooty) deposit on the inside of the jam jar.
Click on the image to read the descriptions.
The importance of being precise
Mum here and assuming you will be playing the CLASSIC 2 Ronnies sketch.....pleeeeease!!! Chemistry and comedy - watch out Cox with your fancy graphics and physics....here comes Dave's Cave - periodic table AND gags!! What's not to love?! xx