Chemical Reactions and Heat Lab

NaHCO3 + C6H8CO7 ⟶ H2O + CO2 + Na3C6H5O7

This is the chemical equation for this experiment. In words, it is sodium bicarbonate and citric acid yields water, carbon dioxide, and sodium citrate. For this experiment, the reactants must come into contact with each other to make a chemical reaction. The reactants are the alka-seltzer tablet and water. After the chemical reaction, we will have our products. The products are water, carbon dioxide, and sodium citrate. In this experiment, we are testing if and how much temperature affects the rate of the chemical reaction.

Hypothesis: If an alka-seltzer tablet is dissolved in water at different temperatures, then it will dissolve faster the hotter the water is and the more water there is. This is because the heat makes the atoms move faster and with more energy, so the water can pull apart the alka- seltzer tablet faster.

Materials:

• Computer
• Vernier Computer interface
• Temperature Probe
• 4 Alka-Seltzer tablets
• stopwatch
• hot plate
• 133 mL of ice
• 665 mL of water
• graduated cylinder
• 600 mL beaker
• stirring rod
• beaker tongs

What we did: We put 266 mL of water into the beaker and heated it to 50ºC. We dropped the alka-seltzer into the water. We recorded the temperature of the water using Vernier and the time using an iPod Touch. We did all of those steps again using room temperature water instead of heating it. Then we did the experiment again using 133 mL of cold water and 133 mL of ice combined. We then did our own trial using only 133 mL of room temperature water.

Data:
Table 1:

Trial name	Temperature	Time to dissolve in seconds	Time to float in seconds
Hot water:	50ºC - 58.6ºC	20.9	instantly
Room water:	20.4ºC - 20.0ºC	38.6	24
Cold water:	0.8ºC - 0.1ºC	110.1	85
Half of Room Water:	20.9ºC - 20.5ºC	42.6	23

The alka-seltzer tablet in the hot water dissolved the fastest and the alka-seltzer tablet in the cold water dissolved the slowest. As the temperature got higher the tablet floated faster. The alka-seltzer tablet only floats when it gets down to a certain size,  so it just reinforces the idea that the alka-seltzer tablet will dissolve faster the hotter the water is. The reason the alka-seltzer tablet in half of the amount of room temperature water floated one second faster is because their was less water for it to float up through, so it hit the surface of the water early.  

This is the graph of the ice water trial. This shows that the temperature fluctuates and it could have affected our data.

This is the ice water. You can see the bubbles and the shadows of the ice cubes. There are bubbles mostly on the side because the tablet moved around the sides of the beaker and left a trail of bubbles. The alka-seltzer tablet was then stopped by and ice cube and left a cluster of bubbles. You can see the white color the alka-seltzer tablet left.

This is the room temperature water. The alka-seltzer tablet moved around the beaker and stayed vertical. It made the water very white and left some residue at the top of the beaker.

This is my sketch of the room temperature water lab. It shows how there are more bubbles and bigger bubbles on the tablet and smaller and fewer bubbles in the normal water.