Why Does The Flame Pull The Water In?

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[dshe]

People tell kids that the water rises to replace the oxygen used up, but actually the hot air bubbles out and when it cools, the pressure drops and sucks up the warer

[Justworkname]

New video title:
“How to waterboard a candle”

[tommontreal]

Each molecule of O2 consumed generates one molecule of CO2. The rising water is due to the hot gases being cooled, and NOT due to "consumption" of oxygen.

[AntMerka]

I'd love to see the effect of this with hot wax instead of colored water and then flash cool the wax sucked into the flask!

[jamieharland]

Wow, I remember learning this school 40 years ago. It must be really new.

[phoenixlewis]

At the beginning he sounds like Dr Mike

[Jrp]

It's not using up the candle flame warms the air which expands and escapes as bubbles which creates a partial vacuum and the higher pressure outside the flask pushes water into the flask.

[nerol]

Instructions not clear, I have 2nd degree burns on

[swr]

The flame using up the oxygen is not what causes it to suck the water up. The hot air inside the breaker is cooling as the flame goes out, and the cooling of the air creates lower pressure inside the breaker. Then atmospheric pressure pushing on the liquid, pushes it up into the breaker.

[pennernderpenner]

The volume of a gas is (to a good aproximation)only dependend on the number of molecules(if temperature and pressure are constant). Which actually increases. 2O2(gas) + Fuel(solid paraffin c20H42 or approx. CH2) --> 2H2O(gas then liquid) and CO2(gas)

However the resulting water quickly condenses into a liquid, resulting in a smaller number of gas molecules and thus smaller volume.

Edit: as others have mentioned, the air escaping in the beginning due to the temperature and thus volume increase also plays a role. Would be nice to see the experiment with a partially prefilled glass. To see only the effect of the chemical reaction.

[victormoor]

So, what happens to the oxigen? Kind of implies that the oxigen "vanishes". Why is the endproduct having higher density?

[mawavoy]

It does not pull the water in. Atmospheric pressure due to gravity pushed the water in . In the beginning the candle heats the air inside the beaker. Pressure increases and a volume of air escapes lowering the pressure inside. Water replaces the escaped air. The water is cooler than the air inside the beaker and cools the air more than the candle increases the air temperature. This lowers the pressure resistance of the remaining air and more water flows in. As the candle’s flame depletes oxygen the flame decreases in size, generating less heat and the pressure decreases more.

[randomergy]

Glad to see you're making videos again (:

[NicholasBuckArt]

Did anyone else feel sad about the flame

[skajekar]

O2 will become CO2, there is no volumetric change there.
Hydrogen in wax becomes H2O and get absorbed into water. That does reduce the volume

[snowwann]

Is this for Jr high?? How do people NOT know this?

[Prof_Jpaz]

This gave me a really nice idea of a double layered candle. Using this method. (Patents pending)

[richardangers]

What is the formula for fluid pressure?
At first the heat increases the pressure inside the glass. As the oxygen is consumed the pressure inside the glass decreases. The pressure outside the glass is unchanged and is pressing on the water in the bowl. It pushes the water up the glass to the point where the remaining pressure inside is sufficient to offset the atmospheric pressure outside ( roughly).

[samyoung]

Atmospheric pressure is higher outside pushing the air inwards!

[adamsteiff]

The flame creates a vacuum as it eats up the air, sucking the water into the beaker. Possibly also giving a demonstration on capillarity.