Observation of a candle mp electricity bill payment online indore


You have seen a candles burn on many occasions, but you have probably never considered the burning of a candle from a chemist’s point of view. In this lab, you will try to determine what is necessary for a candle for a candle to burn, and what products are formed when the candle burns.

3. When a chemical change takes place, a different substance is formed. When a physical change takes place, the substance changes shape or phase, but the substance remains the same. Classify each of the following as a chemical (C) or physical (P) change.

4. Light a second candle and hold the flame 2-4 cm from the flame of the first candle. Gently blow out the first candle flame and then move the other flame in to the smoke from the first flame. Do you have to touch the wick in order to get the candle to relight? Write your observations below. What does this tell you about the part of the candle that is burning?

5. Relight the standing candle and blow out the second candle. Using a tongs, hold the wire gauze over the flame, perpendicular to the flame. Slowly lower the gauze on to the flame. Do not touch the wax. If the flame appears to go out, quickly move the wire gauze to the side. Record your observations. What do you thick is happening? What does this say about the part of the candle that is burning?

6. Place approximately 150 ml of ice water in a 250 ml beaker. Dry the outside of the beaker. Hold the beaker about 4-5 cm above the flame. Look for the formation of a new compound on the bottom of the beaker. Note: you may see the formation of black soot on the bottom of the beaker. That is not the compound that we are looking for. If you see soot, you are probably holding the candle too close to the flame. Record your observations. What do you think the compound is? Where do you think that the compound came from?

7. Pour water in to the pan that the candle is in to a depth of 1cm. Quickly lower the mouth of the Erlenmeyer flask over the candle so that the mouth of the candle is below the surface of the water. Hold the flask in place for approximately one minute. After 1-2 minutes, lift the flask out of water and quickly place the rubber stopper in the mouth of the flask. Record your observations below.

The students should observe that the flame is not touching the solid candle or the melted wax. It appears to be only touching the wick. I ask them if they think that the candle would burn as long if it were only the wick that was burning. What is the purpose of the wax? When the students place the first flame into the smoke of the second candle, they should see the second candle relight. It is not necessary to touch the wick in order for it to relight. This should lead them to conclude that it is the wax vapor that is burning.

When the students place the beaker containing the ice water above the candle, they should see condensation on the bottom of the beaker. If they hold it too close, they will not see the condensation and will see soot form. Students will usually recognize that the condensation is made of water, but they have difficulty recognizing that it comes from the combustion of the candle.

When the Erlenmeyer flask is placed over the top of the candle in the water, student should observe that the water candle goes out and the water rises. The students test the gas that was collected with phenol red solution (an acid-base indicator). They should observe that the solution changes from red to yellow. I demonstrate that this might indicate the formation of carbon dioxide by blowing through a straw into a solution of phenol red.

When students are asked to propose why the water rises in the flask, they come up with a variety of different ideas. Some of these include ideas such as, "all the oxygen was used up and so it created an empty space" or it ‘gets sucked into the flask". You can remind them that carbon dioxide was created and it also takes up space. The new part of this is the extension to the lab. In this inquiry activity, I ask students to try to determine what factors affect how high the water rises and then revise their hypothesis. An explanation as to why this occurs is that the air inside the flask is heated by candle. This causes the air inside the flask to expand and some of it escapes when the flask is placed over it. When the candle goes out and the air cools, it contracts. Since the pressure outside the flask is greater than inside the flask, the water is pushed up into the flask. The collapsing can demo would be a good follow-up activity to this lab. Assessment