Chemical Reactions and Heat Lab

Chemical Reactions and Heat

Problem: What effect does temperature have on the speed of a chemical reaction?

Hypothesis: If the temperature of the water is warmer, the Alka-Seltzer will dissolve faster because the heat of the water will act as a catalyst, and catalysts speed up chemical reactions.

Procedures/Materials: In this experiment Alka-Seltzer was dissolved in water at different temperatures, and then, the time it took for the Alka-Seltzer tablet to completely dissolve was recorded. We started by filling a 600 mL beaker with 266 mL of water. The hot plate was turned on, and the water in the beaker was heated to 50ºC. The temperature of the water was monitored with a temperature probe. When the water reached 50ºC, 1 Alka-Seltzer tablet was dropped into the water. The time it took for the tablet to dissolve was recorded with a stopwatch. Then, the contents of the beaker were emptied, and it was filled with 266 mL of room-temperature water. A thermometer was placed inside to monitor the temperature. Then, an Alka-Seltzer tablet was placed in the water, and the time it took to fully dissolve was recorded. The room-temperature water was emptied, and the beaker was filled with 133 mL of water and 3 ice cubes. The ice water was stirred for about a minute to make sure that the temperature evened out. The thermometer was placed in the beaker to record the temperature. One Alka-Seltzer tablet was dropped in the water, and the time it took to dissolve was written down. The water in the beaker was emptied. For our final test, we were allowed to manipulate any variables we wanted. We had already done tests to manipulate the temperature, so this time we manipulated the amount of water in the beaker. We added 500 mL of room temperature water to the 600 mL beaker. Then, a tablet of Alka-Seltzer was dropped in the water, and the time for it to dissolve was recorded.

Data and Analysis:

The Temperature and Time that it Took the Alka-Seltzer to Dissolve

Temperature of Water (ºC)	Time (s)
50	21.9
22.3	46.2
1.4	257.0
21.1	47.9

This chart shows the different tests that we conducted in this experiment. The first test was with hot water. The second test was with room temperature water. The third test was with ice water, and the fourth test was with room temperature water, but the amount of water in the beaker was increased. 

This graph shows the temperature at the different points in our data collection. We started with the 50ºC water that is represented by the inclined part of the graph in the beginning. Then the diagonal line that goes down connects that part of the graph to the room temperature part because we chose to append all the data runs together. The flat part of the graph towards the middle is the first room temperature test. Then, there is a straight line going down to connect the room temperature run with the ice water test. The ice water test is shown with the flat part of the graph at the bottom. The final diagonal line connects the third test with the fourth room temperature test that had more water in it than the others. The little dip at the end is the temperature probe being wiped with a paper towel because we forgot to press stop! :)

This graph is a better representation of the data points that we collected during this experiment. It shows that as the temperature of the water decreased, the time it took for the Alka-Seltzer tablet to dissolve increased. 

This is how the lab was set up. The water was in the beaker, and the table was dissolving while the temperature was being monitored with a temperature probe.

This is an image of the Alka-Seltzer tablet dissolving in 500 mL of room temperature water. This was the test where we were allowed to choose our own variables.

This is the tablet dissolving in ice water. It took the tablet the longest time to dissolve in the ice water.

Conclusion: This experiment was a successful, interesting experiment. I learned a lot about speeding up chemical reactions and the effect that heat has on it. My hypothesis was somewhat rejected and somewhat accepted. I was correct that if the temperature gets warmer, the tablet will dissolve faster, but I was incorrect about heat being a catalyst. Heat was just a variable used to speed up the chemical reaction. The reason that heat speeds up a chemical reaction is because for chemical reactions to take place there must be many collisions between different atoms. Collisions between atoms require energy, and heat is a form of energy. Therefore, introducing heat to a chemical reaction will speed up the process because the atoms will have more energy to collide with each other. For the test that we were allowed to determine the variables, I was surprised that the amount of water did not have an effect on the time it took to dissolve. I thought that it would have made the tablet dissolve faster because there were more atoms to make collisions with. Since the amount of water did not have much of an effect, it was proven that heat is the best way to speed up a chemical reaction. I could use the data that I collected to see if heat will affect a different chemical reaction such as lead nitrate and potassium iodide. Despite having trouble collecting the data with Logger Pro, this experiment was interesting because I finally understand how heat affects chemical reactions.