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What is the independent variable in this experiment?
What is the dependent variable in this experiment?
What is the control in this experiment?
What are the constants in this experiment?
Write another hypothesis that could have been tested by this experiment.
Why was it important not to let the thermometer rest on the bottom of the beaker?
Salt is often spread on roads during winter to prevent ice from forming. Do you think sugar would work as well? Explain your answer.
Did the student use good scientific methods &tring this experiment?
Objective: I know that pure water freezes at 0oC, so I want to see how
adding different substances to water changes the freezing point. I will
measure the freezing point of pure water, water mixed with salt, water mixed
with sugar, and water mixed with alcohol.
Hypothesis: The saltwater solution will have the lowest freezing point.
Details of the Experiment: First, I made my solutions. I poured one cup of
water into Beaker 1 and set it aside. I poured one oup of water into Beaker 2
and then added one tablespoon of salt, stirring the solution until the salt was
completely dissolved. I poured one cup of water into Beaker 3 and then
added one tablespoon of sugar, again stirring the solution until the sugar was
completely dissolved, I poured one cup of 40 percent isopropyl alcohol-the
other 60 percent is pure water-into Beaker 4.
Next, I made a mixture of slurry ice in a large bowl by combining water,
ice, and salt. I placed Beaker 1 into the slurry ice mixture and began stirring
the pure water with a thermometer. I made sure the thermometer didn't touch
the bottom of the beaker as I stirred, As soon as ice crystals began forming
on the water in the beaker, I read the temperature on the thermometer and
recorded the result. I repeated this procedure for the other three solutions.
Itesults: Freezing point of Beaker 1 (plain water): -0.5"C
Freezing point of Beaker 2 (saltwater solution): -4.5"C
Freezing point of Beaker 3 (sugar water solution): -4.5'C
Freezing point of Beaker 4 (40% isopropyl alcohol): -17 .5'C
Conclusion; My hypothesis was not cotrect. A solution of alcohol and water
will lrave the lowest freezingpoint.
Comments: I was surprised to see that both the sugar ancl salt solutions had
the same freezing point. I also thought that alcohol, which is a liquid, would
affect the freezing point less than a solid, like salt or sugar,