Hot and Cold Water

The purpose of the experiment is to test boiling and freezing points of both hot, cold, salt and unsalted water. The three experimental questions I followed for this were: 

1. Does hot water or cold water freeze faster?

2. Does hot water or cold water boil faster?
3. Does salt water boil faster or slower than regular water?

The first step was for me to formulate several hypotheses for each experimental question. 

1.  Hot water has faster moving molecules and will freeze slower than cold water

2. Because  hot water is at a higher temperature it will take less time to boil than cold water

3. Adding salt to the water will increase the volume of molecules and cause the boiling time to increase.

This experiment deals primarily with the movement of molecules and the three states of matter: solid, liquid and gas. Molecules move at different speeds in the three states, and in a hot and cold situation. Below is a video on the various movement speeds in the three states of matter. 

https://www.youtube.com/watch?v=v12xG80KcZw 

 This next video shows examples of molecules movement at different speeds. 

https://www.youtube.com/watch?v=evteZ-FN0hY

Water molecule

This is what the molecular structure of water molecules looks like

Materials Needed

For this experiment I used

6 standard sized red plastic cups

1/2 tablespoon of salt

2 cups of water for boiling

1 small pot

measuring cup

Morton iodized salt

an electric stovetop

a Kenmore brand freezer

Experiment setup

Below are photos of the experiment and the setup used.

The pot and measuring cup used as well as the stovetop

The cups used to be put in the freezer with labels

Location of cups in the freezer (top rack bottom left corner)

Materials used for boiling and measuring. Included is also the type of salt used

the thermometer used to measure the temperatures

Independent and Dependent Variables

• for experiment 1 the independent variables were the water temperatures of hot and cold for each cup. The dependent variable was the time it took for the water to freeze. The control was using the same tap water from the sink.
• For experiment two the independent variable was the water temperatures of hot and cold. the dependent variable was the time it took to boil. The control was using the tap water from the sink.
• For experiment three the independent variable was adding salt to the water. The dependent variable was the time it took for the water to boil. The control was using the tap water from the sink each time.

Procedure for experiment 1 Freezing Hot and Cold Water

For this experiment, I used the tap water from the sink at my house. I used the curved lines on the side of each cup as my measurement device and filled each cup to the top of the curved lines. The faucet temperature was turned to both the hottest setting and the coldest setting. Each time the water was measured using a cooking thermometer. The experiment was started at 10:15 in the morning and each test was completed at separate times throughout the day. For each round, a new cup was sued and labeled with fresh water. 

Procedure for experiment 2 Boling hot and cold water

The first step was to measure set the sink to the hottest setting and measure out two cups of water into the pot. After both cups were added the water temperature was measured and recorded. The burner was turned to the highest setting (for this model it would be an 8). A timer was set and once the water was boiling ( bubbles were being created and moving through the water rapidly) the timer was stopped. The pot was removed from the burner. These same steps were repeated for the cold water test. The sink was turned to the coldest setting and two cups were measured. A new burner was used for each round of testing. The pot was also given time to cool down.

Procedure 3 Boiling salted water and unsalted water

For this experiment tap water for the sink was used at the neutral position of the sink. Temperatures were measured for each round. For the first test 1/2 tablespoon of salt was added to the two cups of water per test. The pot was placed on an unused burner and put on the highest setting (the model allowed for the highest setting to be 8). A timer was set from when the burner was turned on until the water began to boil. The water was poured out and the pot was given time to cool down.

Data and Analysis

Hot water boil

Temp 104.3	Time to boil: 4:05
Temp 104.5	Time to boil: 5:47
Temp 103.8	Time to boil 5:05

Cold water boil

Temp 58.4	Time to boil 5:30
Temp 56.1	Time to boil 7:04
Temp 59.1	Time to boil 6:00

 

Saltwater boil

Temp 90.7	Time 6:26
Temp 85.6	Time 6:14
Temp 79.1	Time 4:30

No salt water boil

(a) Temp 87.8	Time 7:17
(b)Temp 88.3	Time 9:45
(c) Temp 86.7	Time 6:12

Cold water freeze

Temp 55.3	Time to freeze 7:42pm- 9:35pm 1 hour 53 minutes
Temp 59.6	time 10:21 am- 11:40 am 1 hour 21 minutes
Temp 53.7	Time 11:45 to 1:45 pm 2 hours

Hot water freeze

106.4	Time to freeze 7:42pm-9:15 pm 1 hour 27 minutes
109.1	Time to freeze 10:21 am- 11:25 pm 1 hour 4 minutes
104.6	Time to freeze 11:45 am to 2:15 pm 2 hours 30 minutes

Repeatability

For each experiment, it was able to be repeated multiple times. Each trial was in a 15-degree range for, the two states of temperature (hot and cold). For the second trial, 1/2 tablespoon of salt was added to the two cups of water. If this experiment was to be repeated again more or less salt could be added for a second independent variable. For the freezing water, this was also repeated three times. it could be done again by using different amounts of water and a different location in the freezer. Overall, these experiments are simple enough to have changed and repeated to find similar results.

Theories Resulting  From the Experiment

Molecules can move through the various states of matter and depending on the base temperature this changes the speed. Looking at the first experiment of the water boil, the higher temperatures had a faster time to boiling. The boiling point of water is 212 degrees Fahrenheit and having hotter water meant it was already close to the boiling point. Now, using this information it also means that because the water is close to the boiling point it will take longer for the molecules to freeze. Molecules also move faster and more freely in a warm liquid state. When molecules are in a solid state of matter they vibrate and cannot move as freely. Cold water can reach the freezing point (32 degrees Fahrenheit) faster. 

Now, the salt was is considered a solution in this experiment. The salt is considered to be the solute and the water is the solvent. Adding salt to the water also increases the volume of what is in the pot. But, it takes less energy to heat saltwater than regular water which brings the time down for boiling the water.

Overall Conclusion

There were several scientific concepts in these experiments. The first was the three states of matter. Aside from plasma (which was not seen in this) solids liquid and gas are the main three. The transformation of each state into another was observed in the experiments. Liquids moved into a solid state and liquids were heated and moved to a gas state. The next concept looked at was the molecular structure and speeds for the states of matter. Solids move at sower speed and vibrate rather than move. When heated the molecules vibrate faster. Liquids have more space to move around. The main structure that was examined in this experiment was water H2O. It is composed of two hydrogen atoms and one oxygen atom. Boiling and freezing points were also used in the experiment. The boiling point is 212 degrees Fahrenheit and the freezing point is 32 degrees Fahrenheit.

Each experiment had a different question. Does hot or cold water boil faster? Does salt water boil faster than cold water? Does hot water freeze faster than cold water? Each experiment was repeated three times for accuracy. For boiling the hot and cold water for two out of three trials the hot water boiled faster. For the second experiment, the nonsalted water boiled slower two out of three times. For the freezing water experiment, the hot water froze faster two out of three times.

The biggest question is what is the importance of the experiment. Understanding the uses of hot and cold water is very important in the culinary world. When pressed for time people want the simple act of boiling water should take the least amount of time and energy as possible. The same goes for freezing water. These also help us understand more about what affects the different states of matter. Heat, solutes, solvents, and temperature all can have a change of the states of matter.