As we have learned in science class, most of our transportation is powered by fossil fuels. When fossil fuels are burned, harmful greenhouse gases and pollutants are placed in the air. Fossil fuels are considered to be non-renewable sources of energy, because they come from the remains of living things more than 300 million years ago that can in no way be replenished at the rate at which we humans are using them! Therefore, we designed experiments to determine how best to propel rockets using Alka-Seltzer + water as a model of an alternative and renewable source of energy.
Before designing our experiments, we made some observations of other chemical reactions to get a better sense of how to design our own experiments.
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As with every controlled investigation, we only change one variable in order to observe the effect(s) of that one change. Think back: What was the ONE variable that your group decided to change to the Alka Seltzer + water chemical reaction? What is another way to describe the ONE variable that a scientist changes in an experiment? What is another way to describe what the scientist measures?
Each group only changed one variable in order to see the effect(s) of that one change. Some groups changed the temperature of the water or the amount of water, while other groups changed the size of the Alka-Seltzer tablet. The group above changed the temperature of the water, and predicted that the hotter water would dissolve the tablet faster.
As a scientific community, we shared our group's results. Through our first round of experimentation, we learned that increasing the temperature, increasing the amount/volume of water, and crushing the Alka-Seltzer tablet all decreased the amount of time it took for the Alka-Seltzer to dissolve (for the chemical reaction to occur).
As a scientific community, we shared our group's results. Through our first round of experimentation, we learned that increasing the temperature, increasing the amount/volume of water, and crushing the Alka-Seltzer tablet all decreased the amount of time it took for the Alka-Seltzer to dissolve (for the chemical reaction to occur).
Before designing our rockets, we took a break and visited the animals! What was your favorite animal at the Environmental Study Center?
After experimenting to better understand how the size of Alka-Seltzer, temperature and volume/amount of water affect the speed of the chemical reaction, each group picked one variable (= independent variable) to change to their Alka-Seltzer powered rocket to get the rocket that can propel the highest. Most groups changed the temperature or size of the Alka Seltzer. Do you remember which group had the highest rocket propulsion? Do you remember this group's independent variable?
After experimenting to better understand how the size of Alka-Seltzer, temperature and volume/amount of water affect the speed of the chemical reaction, each group picked one variable (= independent variable) to change to their Alka-Seltzer powered rocket to get the rocket that can propel the highest. Most groups changed the temperature or size of the Alka Seltzer. Do you remember which group had the highest rocket propulsion? Do you remember this group's independent variable?
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Last but most certainly not least, we learned that there is no such thing as failure in science. There is also no such thing as an "incorrect" hypothesis, because the whole point of testing a hypothesis is to learn something new (and learning something new is never wrong/right/correct/incorrect). Instead, we say that our hypothesis was "not supported" and reflect on the process and possible limitations that occurred in the planning/design and execution of the experiment, and also evaluate and possibly re-think our original hypothesis!
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