The Great Candle Experiment

This experiment is often done and is always a lot of fun.  During this science lesson it promoted a lot of discussion about what we thought was happening.

What to do:

1. Stick a candle onto a plate with plasticine.
2. Pour some coloured water onto the plate.
3. Light the candle.
4. Carefully lower a jar over the top.
5. Observe what happens.

What we observed:

• The water was slowly sucked into the jar.
• The candle slowly went out.
• When the candle went out the smoke went straight up.
• When the candle went out lots of water was quickly sucked up into the jar.
• There were some bubbles around the jar as the water was sucked in.

Carefully lower the jar over the candle.

What can you see happening?

This small candle burnt for a long time.

Wow - lots of the water has been sucked up into the jar.

This little candle worked the best.

We could see some bubbles around the jar.

Click on this link to find out why this happens.

Extinguishing a Candle

For a flame to burn it needs 3 things:

• Oxygen
• Fuel
• Heat

This is called the Fire Triangle. If you remove one of these things the flame will be extinguished.

This week the science club students investigated what would happen if they put a jar upside down over a candle. They predicted that the flame would go out because all the oxygen would get used up.

The students had to observe the flame carefully to ensure it had gone out before they lifted off the jar. Sometimes the flame was not out and when the jar was lifted oxygen got to the candle and the flame got bigger.

Then they used a range of jar sizes to see if this made a difference to the time the flame burnt for.
After 1 test they found out that the candle in the small jar extinguished before the candle in the large jar. However, they decided to do more testing just in case this was a coincidence.

After more trials they found out that every time the candles in the smaller jars were extinguished the quickest.

Why does this happen? Everyone decided that it was because the biggest jar had the most oxygen inside it so the flame could burn for longer. As the candle burnt it used up the oxygen and gave out carbon dioxide. The carbon dioxide would also help to extinguish the flame. 

They also  found out that there are many changes that occur when a candle burns.

So what is produced when a candle burns?

• You sometimes get smoke and soot (which is particles of partly burnt wax)
• The wax changes into melted wax.
• Carbon Dioxide and Water are produced from the chemical reaction between the oxygen and the fuel in the flame.

Science Club 2014

Yay!  The Year 5 and 6 Science Club has started again for 2014.  The theme of our learning this term is burning and heat.

The first lesson was about candles and what makes them burn.

Here is our equipment for the lesson.

To keep safe we had some water handy.  Just in case!

First we had to carefully observe the candle and take notes about it before we lit it.

We recorded our observations carefully.

Does the candle have a smell?

Next we lit the candle and observed changes to the candle.

After predicting what we thought would happen we recorded what we observed.

We started thinking about how and why a candle burns.

We think that the wick burns first and this melts the wax.  The liquid wax wicks (moves up) the wick and the gas formed from the wax floats around the wick.  The gas is what is burning.

We also think the hottest part of the flame is around the wick and the blue part at the bottom.

Around the flame we could see a faint haze.

Tune in next week to find out what else we find out about burning.