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Title : Quantitative Observations of a Chemical Reaction

 

Purpose:

            Make a quantitative investigation of a chemical reaction.

 

Procedure :

  1. Find the mass of the candle, including the glass plate.
  2. Measure exactly 100mL of tap water in a graduated cylinder.  Pour the water into a 250mL beaker and place the beaker on wire gauze.  Measure the temperature of the water
  3. Light the candle and place it on the glass square, as shown.  Adjust the height of the ring so that the flame is about 2cm below the base of the beaker.  Using the candle, heat the water for exactly 10 minutes.  Extinguish the flame and measure the temperature of the water and mass of the candle with the glass square.
  4. Relight the candle and repeat steps 1-3 for a second trial.

 

Data / Observations:

                                                            Trial 1                          Trial 2

-Original Mass of candle -                    25.81g                         24.65g

-Mass of candle after burning-  24.65g                         23.70g

-Time candle burned-                           10 mins                        10 mins

-Original temperature of water- 27C                            28C

-Final temperature of water-                 45C                            45C

-Time water heated-                             10 mins                        10 mins

 

Analysis / Calculations:

1) The change in mass of the candle

            Trial 1

                               Change in mass 1.16 grams

            Trial 2

                                Change in mass - .95 grams

2) The change in the mass of the candle per minute

            Trial 1

                        Change in mass per minute - .116g/min

            Trial 2

                       

                                                                        Change in mass per minute- 9.5x10-2g/min

3) The change in the temperature of water

            Trial 1

                             Change in temperature of water 18.0C

            Trial 2

                             Change in temperature of water 17.0C

4) The change of temperature of water per minute

            Trial 1

                          

Change in temperature per minute 1.80C/min

            Trial 2

                       

                                                            Change in temperature per minute 1.70C/min

 

Questions

1) Compare your trial results and calculations with those of other lab teams.  Are your results exactly the same? How do you account for any differences in data?  If one set of data differs from another in an experiment, does this mea that one or both sets are wrong?  Explain your answer.

The results are not exactly the same.  The differences in data could be caused by a different original mass of candle, or a different original temperature of water.  These errors would cause the other measurements to differ.  Neither of the experiments is wrong because in a science experiment there is always a percent error, and as long as the trials were all within expectable percent error, they would all be considered correct.

2) What does the term rate mean?   a. What was the rate of burning of the candle?  B. What was the rate of heating of the water?

    Rate is the speed at which something occurs.  a The candle burned at a rate of approximately .1 gram/min.  b The water was heated at a rate of approximately 1.75C/min.

3) Explain how the heat from the combustion reaction is related to the temperature change of the water.

The heat caused by the combustion reaction is transferred to the water by conduction and convection currents.

4) Outline a laboratory procedure that would determine which produces more heat a gram of candle wax or a gram of alcohol.  How could this type of experiment be used to decide which substance would make a better fuel?   What other factors might enter into choosing a fuel?

Put both of the substances into individual controlled environments.  Simultaneously light the candle wax and the alcohol.  Measure the difference in temperature from before and after the materials was burned.  The controlled environment with the greatest increase in temperature will yield the substance that would work as a better fuel.

Factors that would need to be taken into consideration may be how long each fluid will burn because the fuel may need to be light for an extended period of time, where the alcohol would be out of the question because of the amount of fuel it would require to allow it to burn over an extended period of time.

 

Conclusion:

            The transfer of heat from the candle to the beaker, and then toward the water caused the water temperature to rise, and when the flame was removed, the temperature of the water drastically dropped.  For every .116 grams of candle burned, the water temperature increased approximately 1.75C.