Discussion
1. Hypotheses and results:
Our hypotheses are mainly correct.
In part1 (effect of temperature) we predicted that the warmer the water is, the faster the reaction will be. From our observation, the Alka Seltzer tablet took the longest time when dissolved in cold water and took the shortest time when dissolve in hot water; these observations prove our hypothesis. Heating causes the particles (atom and molecules) of the reactants to move more quickly, resulting in more collision, so chemical reaction happens quicker.
For part2 (effect of concentration), we predicted that the higher the concentration (HCL) is, the faster the piece of zinc metal will dissolve. Our results also proved the hypothesis. When we put the zinc metal the HCL with the highest concentration (1M), it took the shortest time to dissolve and when we put the zinc metal in the HCL with the lowest concentration (0.01M), nothing happened. If there is a greater concentration of reactant atoms and molecules present, there is a greater chance that collisions among them will occur. More collisions mean a higher reaction rate.
In part3 (effect of surface area) we predicted that the larger the surface area is, the faster the reaction will be. From the observation of out experiment, we found that the Alka Seltzer took the longest time to dissolve when it was a whole tablet and took the shortest time to dissolve when it was crushed. It proved out hypothesis. The greater surface area of the tablet allows water molecules to collide with many more atoms per unit of time.
In part4 (effect of the presence of a catalyst), we predicted that the copper chloride will cause the fastest Hydrogen peroxide’s decomposition. Our result shows that the Hydrogen peroxide takes the shortest to react when copper chloride is added. This proved our hypothesis.
2. Procedures, variables and controls
For part 1 of our experiment, we put 1 Alka Seltzer tablet in each kind (cold, warm and hot) of water of same amount and recorded the time the tablet took to dissolve in each. We controlled the amount of water (100ml), and the amount of the Alka Seltzer tablet (1 for each kind of water), but changed the temperature of the water because we want to make sure that the change of temperature is the only factor that effects the change in rate. Independent variable here is the temperature of the water, dependent variable is the rate (time in sec) for the Alka Seltzer tablet to dissolve and the controlled variables are the amount of water, and the amount of Alta Seltzer tablet.
In part 2 of our experiment, we put zinc metal (in same size) in each kind of HCL with different concentration (0.01M, 0.5M and 0.1M), and recorded the time the tablet took to dissolve in each kind of solution. We controlled the amount of HCL solution and the size of the zinc metal, but changed the concentration of HCL it makes sure that the only factor affect the result is the concentration of the HCL solution. The independent variable here is the concentration of HCL, the dependent variable is the time that zinc metal takes to dissolve and the controlled variables are the amount of HCL and the size of the zinc metal.
In part3 of our experiment, we threw Alka Seltzer table in different shapes (different surface areas) into the water of same amount, and record the time each kind of tablets dissolve in the water. We controlled the temperature of water, the amount of water and the amount of tablets but changed the surface area by cutting the tablet into chunks and crush it. The independent variable is the surface area of the tablets; the dependent variable is the rate that the tablet to dissolve in water and the controlled variables are the amount of water, temperature of water, and the amount of Alka Seltzer table (1 tablet).
In part 4 of our experiment, we put different kinds of compounds into the hydrogen peroxide and observe what happen. We controlled the amount of hydrogen peroxide and the amount of each compounds to make sure that the change of compounds are the only factor that affect the rate of decomposition. The independent variable is the different kinds of compounds, the dependent variable is the rate of decomposition and the controlled variable is the amount of hydrogen peroxide and the amount of each compound.
3. Results Discussion
According to the graph of part1, the time Alka Seltzer tablet uses to dissolve in water decreases as the water becomes hotter and increase as the temperature becomes lower. We get the result that the higher the temperature is, the faster the tablet dissolve, chemical reaction speed sup; the lower the temperature is, the slower the tablet dissolves, chemical reaction slows down. It corresponds to the theory.
According to the graph of part2, the time zinc metal uses to dissolve in water decrease as the concentration increase, and increases as the concentration increase. We would draw the result that the higher the concentration of the solution is, the faster the zinc metal dissolve, chemical reaction speeds up; the lower the concentration of the solution is, the slower the zinc metal dissolves, chemical reaction slows down. It corresponds to the theory.
According to the graph of part3, the time Alka Seltzer Tablet uses to dissolve water decreases as the surface of the tablet decreases and increases as the surface area of the tablet increases. The larger the surface of the tablet is, the faster it dissolve in water, chemical reaction speeds up; the smaller the surface area of the tablet is, the slower it dissolve in water, chemical reaction slows down. It corresponds to the theory.
Table of Observations for Catalyst Reactions
catalyst3.docx | |
File Size: | 67 kb |
File Type: | docx |