I need ho design an experiment on the dissolution of NH4NO3 in water. My independent variable is the amount of solvent (water) while my dependent variable will be the difference in temperature before and after the reaction. What could the hypothesis and scientific reasoning be?
<<The energy needed to break the bonds between the ammonium and nitrate ions is greater than the energy evolved between the ammonium and nitrate ions and the water molecules>> so temps go down.
I dont recommend this as a experiment, as you are relating temp vs how much water has been added...First, if say you had some solution, the temp went down to to XXC. Then you added more water..at another temp...the temp will change for two factors: one, you diluted the solution, but more importantly, you added water at another temperature. You will have no way to separate the effects, and certainly no scientific reasoning.
What you can do, is make the independent variable the amount of ammonium nitrate added, and then measure temp change.
Hypothesis: temp goes down because of what I cited in the <> above.
Hypothesis:
Increasing the amount of solvent (water) in the dissolution of NH4NO3 will result in a greater difference in temperature before and after the reaction.
Scientific Reasoning:
The dissolution of NH4NO3 in water is an exothermic process, meaning it releases heat. By increasing the amount of solvent (water), there should be more molecules of water available to interact with the NH4NO3 particles, leading to a greater number of interactions and a higher overall heat release.
To design the experiment, you can follow these steps:
1. Materials and Setup:
- NH4NO3 (ammonium nitrate) crystals
- Distilled water
- Thermometer
- Beakers
- Stirring rod
- Calorimeter (insulated container to measure heat changes)
2. Experimental Procedure:
a. Start with a fixed amount of NH4NO3 crystals (e.g., 10 grams) in each experiment.
b. Gradually increase the amount of water used as the solvent (e.g., 50 mL, 100 mL, 150 mL, etc.), while keeping the amount of NH4NO3 constant.
c. In each trial, measure and record the initial temperature of the water and the NH4NO3.
d. Carefully add the NH4NO3 crystals to the water and stir gently to fully dissolve.
e. Continuously monitor and record the maximum temperature reached during the dissolution process using a thermometer.
f. Calculate the difference in temperature before and after the reaction for each trial.
3. Analysis and Conclusion:
a. Graph the amount of water (independent variable) against the difference in temperature (dependent variable).
b. Analyze the data: observe the trend and patterns in the graph.
c. Draw conclusions based on the results. Compare the differences in temperature for each amount of water used. Determine if there is a clear relationship between the amount of water and the temperature difference.
d. Discuss any unexpected results, possible sources of error, and suggestions for improvement in future experiments.
Remember to ensure safety throughout the experiment by following proper lab protocols and precautions.