Experiment

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Last updated 3 years ago

Discipline:
Science
Subject:
Experiments
Grade:
8

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Experiment

EXPERIMENT

Our Question

?

?

Our Equipment

Method

What did we do?

My Prediction

What I think will happen?

If I put a teaspoon of sugar, salt, and baking soda in different cups of water filled with 1 cup of tap water then I put all the cups in the freezer, then the cup filled with fresh water will freeze first, followed by the sugar, then the baking soda, and finally the salt because the ingredients will affect the freezing points of water and the salt will change it the most. I will also do the same with 1/2 teaspoons in 1/2 cups of water.

Will adding equal amounts of baking soda, salt, and sugar to three different cups of water affect the freezing time of the water if they are all put under the same amount of cold for the same amount of time?

Analysis: The cup without any added ingredients froze first, followed by the sugar, then the baking soda, and finally the salt. My research pointed to this result as well saying that adding ingredients will lower the freezing point of the water causing it to take longer. One of the reasons we put salt on the icy roads is to melt the ice. This experiment did the same. The salt water took longer to freeze because the salt was constantly melting the ice crystals forming. When the baking soda was frozen, all the powder was on the top of the ice. The ice cube with baking soda was not transparent because of the white baking soda particles in it. The baking soda did not dissolve into the water which I think is why the ice was powdery and it did not freeze fast. The sugar dissolved into the water which made it freeze faster than the baking soda. Although the salt dissolved in the water, it was preventing the water from freezing because it thaws the ice. Conclusion: My data supported my hypothesis because I said the order of freezing would be water, sugar water, baking soda water, salt water and it was. The water took about 130 minutes to be completely frozen (when I flipped the cup upside down and took out the ice it did not have any puddles at the bottom of the cup). The sugar took about 140 minutes. The salt and baking soda froze late in the night so I do not have an exact time but I would estimate about 180 minutes for the baking soda and 210 minutes for the salt. The errors I may have made would be starting the project a little late in the day and not checking on the salt and baking soda after I had to go to bed. The sugar and water were relatively close in freezing time but the salt and baking soda took a lot longer because the salt melts the ice as it freezes and the baking soda lowers the freezing point of water more than the sugar does. When I did the same experiment with half the materials, the waters froze in the same order but the water froze at 110 minutes, the sugar water froze at 130 minutes, the bakig soda water froze at 150 minutes, and the saltwater froze at 160 minutes.

Research: Sea water (salt water) freezes at about 28.4 degrees Fahrenheit, while fresh water freezes at 32 degrees Fahrenheit. When saltwater freezes it freezes only the water part so there is not a lot of salt in the actual ice. This is why people put salt on the icy roads to melt it. So the salt water should freeze after the fresh water (NOAA). Sugar in water is also supposed to lower the freezing point of water (Mike M.). So the sugar water should also freeze after the fresh water. Baking soda is supposed to also lower the freezing point but it is supposed to lower it more than sugar does so this should also freeze after the fresh water (Barchok). According to Philip Schmidt, when tested on a frozen driveway, the baking soda worked about half as well as the salt did, but it did melt some of the ice (Schmidt 2012). William Lynch said that sugar melts ice but not nearly as well as salt (Lynch). Procedure:1. Pour 1 cup of water into four plastic cup 2. Let water sit for about an hour until they are all around the same temperature3. Put 1 tsp of kosher salt into one cup, pour 1 tsp of granulated white sugar into another cup, and pour 1 tsp of baking soda into the third cup4. Stir each of the mixtures until there are very few particles on the bottom of the water5. Put each of the cups in the freezer at the same time6. Start recording the time the cups have been in the freezer7. Check on the cups every 5-10 minutes until frozen8. Now do the same procedures except use 1/2 cup of water and 1/2 tsp of ingredients

Results

What happened ' Why?

Kosher saltGranulated white sugarTap waterTeaspoons and cupsBaking sodaA freezerPlastic Cups

References: Schimdt, "We Tested It: Homemade Driveway Deicers: Find out what's in your cupboard (or garage) that will melt ice." http://www.networx.com/article/we-tested-it-homemade-driveway-deicers, (3/3/15)Lynch, "Why Does Sugar Melt Ice?" http://www.ehow.com/facts_5764444_sugar-melt-ice_.html, (3/4/15)NOAA, "Can the ocean freeze?", http://oceanservice.noaa.gov/facts/oceanfreeze.html, (3/12/15)Barchok, "Re: How does sodium bicarbonate (baking soda) affect water's boiling point?" http://www.madsci.org/posts/archives/1998-05/896128508.Ch.r.html, (3/6/15)Mike M., "sugar water freezing", https://van.physics.illinois.edu/qa/listing.php?id=1633, (3/7/15)


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