Activity #1 Hot or Cold Water?

Experimental Questions
#1 Does Hot water or Cold water freeze faster?
#2 Does Hot water or Cold water boil faster?
#3 Does Salt water freeze faster or slower than regular water?

Hypothesis
#1 Hot water will freeze faster because the molecules are moving faster.
#2 Hot water will boil faster because again, the molecules are moving faster.
#3 Salt water will freeze slower than regular water because the Na molecules bind to the water molecules to create a new molecule.

Answers to Experimental Questions
#1 Hot water froze faster
#2 Hot water boils faster than cold water.

 #3 Room temperature water froze faster than room temperature water with salt.

	Does cold water or hot water freeze faster?
	½ Cup Cold water @ 46.9 degrees F	½  Cup Hot water @ 98 degrees F
	Freeze Time	Freeze Time
Test #1	2 hours and 24 min	2 hours and 17 min
Test #2	2 hours and 25 min	2 hours and 20 min

	Does hot water or cold water boil faster?
	½ Cup Cold water @ 46.6 degrees F	½ cup water @ 98.2 degrees F
	Boil Time	Boil Time
Test #1	1 minute and 55 seconds	1 minute and 7 seconds
Test #2	2 minute and 3 seconds	1 minute and 11 seconds

	Does salt water freeze faster than regular water?
	½ cup water with 2 tsp. of salt @ room temp	½ Cup Water @ Room Temp
	Freeze Time	Freeze Time
Test #1	2 hours and 45 min	2 hours and 19 min
Test #2	2 hours and 49 min	2 hours and 15 min



Controlled Variables

• The water source used.
• The temperature of the stove top.
• The temperature of the freezer.
• Amount of water used.
• Amount of salt used.
• Beginning temperature of water.

Theories
#1. Hot water will freeze faster than cold water because the hot water is more likely to be supercooled meaning that the hot water's temperature is more likely to cool to temperatures below zero degrees.  In cold water ice crystals form and float to the top forming a sheet of ie over the top of the water creating a layer between the air and the cold water.  Also evaporation occurs with the hot water, and it occurs faster with hot water than it does with cold water.  So since hot water has faster evaporation happen there is less water to freeze. 
#2The rate of heating a liquid depends on the magnitude of the temperature between the liquid and its surroundings.  Cold water absorbs the heat faster while it is cold but once it reaches the temperature of hot water heating the water slows down and it takes just as long to heat the water as it would if the water was hot.  Hot water is already hot and doesnt have to reach the same heat as if it was cold water.  Because it takes cold water longer to reach the same temperature as hot water it clearly takes longer to boil.
#3 It takes salt water longer to freeze than regular tap water because the freezing point become lower. This is why roads have salt poured on them in the winter, because it stops the water on the roads from freezing over as quickly.

Scientific Method

The first step in the scientific method is to ask a question.  We were given three questions to answer and experiment on.  The next step is to do a little bit of background research on the questions asked and possible ways to conduct the experiment to find your results.  I searched information by reading the powerpoint to get some background knowledge on this topic.  The next step or the the third step is to construct a hypothesis.  I constructed a hypothesis for each question that was asked to have experimented on about what I thought the end result would be.  I then tested my hypothesis by costructing an experiment. (pictures of my materials and parts of my setup are pasted above).  The fifth step is to analyze your results which I did by filling in my graph with the time results and trying to understand why I got the results i did. The sixth step is to find out if your hypothesis is correct or not.  I went back and looked at my results and linked them to my hypothesis.  All of my hypothesis were correct according to my results.  The last step of the scientific method is reporting my results which I did by posting them in a graph and repeating my experiment to double check my answers.