Why Does The Candle Flame Point Upwards?

Today is the fifteenth day of the eighth lunar month and many are celebrating the Mid-Autumn Festival. This festival is meant to celebrate friendship, fertility and togetherness and there are a number of traditions associated with celebrating this festival, one of them being the iconic paper lanterns. Lanterns in general are portable lighting devices that comes in various shapes, sizes, and materials with a light source inside usually candles or an electricity-powered bulb. For the Mid-Autumn Festival, candle-lighted lanterns are typically used and which gives a beautiful gentle glow that flickers with the wind.

What is a candle though and how does it provide light? A candle consists of wax and a wick. Most candles are made from paraffin wax, i.e. they are hydrocarbons and are composed of hydrogen (H) and carbon (C) atoms. Just like other hydrocarbons such as the fuel we pump our cars with, wax is the source of energy for the candle. When we light a candle, the heat of the flame melts the wax near the wick, feeding the fire with something to burn. What happens is that the heat of the flame vaporizes the liquid wax and starts to break down the hydrocarbons into molecules of hydrogen and carbon. These vaporized molecules are drawn up into the flame, where they react with oxygen from the air to create heat, light, water vapor (H2O) and carbon dioxide (CO2).

Lanterns lit by candles are used both indoors and outdoors. The candle is placed inside colourful and beautiful paper lanterns that fills the night with colours. However, as most lanterns are made of paper and we all know that paper burns quite easily, why is it that the paper lanterns do not get consumed by the flames from the candle within? Of course if the paper comes in contact with the flame, it will burn but generally, the flame of the candle only point upwards and do not move too far to the side therefore keeping the paper lanterns safe from being burned up. Do you know why the flame point only upwards?

When a candle burns, the flame heats the nearby air and starts to rise. As this warm air moves up, cooler air and oxygen rush in at the bottom of the flame to replace it. When that cooler air is heated, it too rises up and is replaced by cooler air again. This creates a continual cycle of upward moving air around the flame, which gives the flame a teardrop shape. Basically the continuous movement of hot air going up displaces cooler air down to the side which then gets heated up again and move upwards causing the distinctive shape of the flame and which is why it points only upwards.

Something to think about though, if you light a candle in space, how will the flame look like? Do you think it will be the same shape? Does gravity play a role? Let us know if you have the answer by leaving a comment!

Posted by Ayu
Learning Specialist, Petrosains

Aluminium Can Lantern

Lanterns are beautiful and often festive, but did you know that you can make your own out of used aluminium cans? This of course isn’t a new idea and was actually done a long time ago when it wasn’t so easy to buy things and people tend to fully make use of materials around them in order to produce something. Milk cans, bamboo and coconut shells can be used to make lamps and lanterns for use around the house.

The next time you’re enjoying a soda, try collecting the cans. First, clean and dry the cans and then cut lines all around the sides of the cans vertically from up to down like stripes. Refer to the picture above.
Then compress the can by pressing the top and bottom together to gently form the shape of a lamp. The cans can then be spray-painted or decorated, or even left as it is for a more ‘DIY’ look. To get a good even colour though, it must first be sprayed with a white base-coat before painting it in the colour you desire.

The lantern aluminium cans are now ready to be hanged! What I did was to hang them in a spiral pattern for added ‘oomph’ but you can choose to hang them in many ways. In the way I liked it, it takes up to five lamps to get the effect I wanted. As I used it during the recent Raya celebrations, I cut-out shapes of moons and stars from used to give a touch of Raya to the lamp.

To light the lamp, a good source will be battery powered LED lights or small bulbs as these pose no fire risk. A candle will quickly heat up the can and be a burn hazard.

 

Decorations made from used or recyclable materials can be beautiful, interesting and it helps to preserve our environment with only a small cost involved. Do it with your family and friends as a weekend project and let the kids run wild with their imagination!.

Posted by Ayu
Learning Specialist, Petrosains