Home : Patterns : Effect of Concentration
When a candle burns the wax is reacting with oxygen in the air to give out heat and light.
If you give the candle more oxygen then it will burn brighter ... but it will burn out more quickly.
The burning of the candle (a chemical reaction) is affected by the number of oxygen molecules around it.
So the speed of the chemical reaction is affected by the concentration of oxygen
When a candle burns there is a chemical reaction between the molten and the molecules of gas. If the candle has a lot of oxygen it will burn , it will also burn out . The speed of the chemical reaction is affected by the the of the oxygen gas.
Look at the two diagrams below - they are meant to show what happens when one candle gets more oxygen than the other ...
This candle has a low concentration of oxygen so it doesn't burn brightly
The blue circles represent the oxygen molecules and the black line is the candle wick
This candle has a high concentration of oxygen so it burns much more brightly
The candle with more oxygen molecules is said to have a higher concentration of oxygen than the other candle.
We know that the concentration of a molecule will affect the speed of the reaction (the rate of reaction) so a high concentration of oxygen will speed up the rate of reaction.
This means that the candle will burn brighter and quicker.
What gas do candles need for them to burn ?
What part of the candle reacts with the oxygen to make light and heat ?
If the flame is quite small do think the oxygen concentration is high or low ?
If the oxygen concentration is high will the candle burn out in a long or a short time ?
Are the gas molecules moving or still ?
If there are a lot of oxygen molecules in a small space is the oxygen concentrated or dilute ?
Would the candle burn if there wasn't any oxygen ?
Would the candle burn if there wasn't any wax ?
Would concentrated hydrochloric acid react quicker or slower with calcium carbonate than dilute acid ?
Would cold acid react quicker or slower with calcium carbonate than warm acid ?
The reason why the candle burns brighter is that there is a better chance that the oxygen molecules will bump into the molten wax molecules on the wick. If the oxygen concentration is high then that means there are a lot of oxygen molecules moving near the molten wax. With a low oxygen concentration it is less likely that an oxygen molecule will hit the wax - so the candle doesn't burn as brightly.
The reaction between oxygen and wax in a candle gives out both heat and energy. If there is a high concentration of oxygen the candle will give out light. The candle will give out less light if there is a lower of oxygen. This happens because a high concentration of oxygen means that there are a of oxygen molecules near the wax. With a lot of molecules - it is likely that the molecules will bump into the wax.