# Super Saturation Experiment: Hot Ice

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### Teacher Notes

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## Step 1: Getting the Equipment

Okay Step one is finding or buying any the material that you may need. Below there is suggested equipment to be used.
The time of the actual experiment preparation should take in between one to two hours. The presentation is the phase change which can occur in seconds.

## Step 2: Getting the Material

Step two decide what material you have or are going to buy. There are two material options below. Select one do not mix these two. This is because they have very different melting temperature and measurements for water become complex.

## Step 3: Select How Much Material Needed

Step three is finding the amount of material you will be using to for the experiment. This step is mainly for those who chose to use the material sodium acetate in their experiment. Below are charts and graphs that will help you determine how much water is needed to create sodium acetate trihydrate. Sodium acetate trihydrate is water saturated with sodium acetate.

1) Parries hand book data
2) phase diagram of sodium acetate

Determine an amount of water to add as long as there is less water per sodium acetate (for people have trihydrate use the trihydrate row) needed to dissolve all the sodium acetate at room temperature (about 20 degrees Celsius). The measurement needed should look something like: (x amount of sodium acetate)/(100g of water) at 70 degrees Celsius. x in this case will be 146g of sodium acetate in this case. for picking the temperature it is highly recomended picking 70 degrees Celsius. When heating the solution we will heat it higher than you measured for so that water is fed in excess. This is so no sodium acetate crystals are left, just one will mess up the experiment.

The phase diagram is more for sodium acetate trihydrate showing that its okay to add water to solution, but adding to much will alter the experiment.

## Step 4: Review Safety

Step four is reviewing safety. Before even starting an experiment you should read the safety information about the reagents. The safety information may be found online or on the side of the bottle. Sodium acetate and sodium acetate trihydrate have the same safety measures.

Sodium Acetate (Safe for class use) NFPA Rating: (estimated) Health: 1; Flammability: 1; Reactivity: 0

Hazards
Eye: May cause eye irritation.
Skin: May cause skin irritation.
Ingestion: Ingestion of large amounts may cause gastrointestinal irritation.
Inhalation: No hazard expected in normal industrial use.
Chronic: No information found.
First aid
Eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Get medical aid.
Skin: Get medical aid. Flush skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse.
Ingestion: If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid.
Inhalation: Remove from exposure to fresh air immediately. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical aid if cough or other symptoms appear.
Notes to Physician: None
Physical properties
Clean up: Is water soluble, use water and dispose of properly.

## Step 5: Measuring the Material

Step five is where the action of measuring out the material takes place. Using a weigh boat measure your calculated amount of sodium acetate needed in part three*. Measure the sodium acetate in on your chosen scale. If you are using option one then you will need to use water too. Measure out your calculated corresponding amount of water from parries handbook**. Add measured content to a beaker.

*If you have sodium trihydrate measuring the amount is not necessarily needed, but is good practice.

**If using option two use column two in parries handbook (recommended temperature 30 degrees Celsius or lower), this is optional for option two.

Material used: option one, option two.
Suggested Equipment: Large Weigh boat, graduated cylinder 100mL, beaker 250mL, electric scale.

## Step 6: Heating the Solution

Step six is a mildly difficult step. in this step you will be heating the solution melting any sodium acetate trihydrate.

Option one: Here you will place you beaker holding the solution onto a heating device where you may heat the solution to around 70 degrees Celsius*. Stirring with a stir rod is recommended for two reasons while heating the solution. The first reason is to stop sodium acetate trihydrate from burning if heated at hot temperatures. The second reason is to make sure all the solution has melted. A thermometer is also recommended for an accurate read of the temperature of the melted solution. This step should take about 10 to 15 minutes**.

*Sodium acetate trihydrate melts around 58 degrees, however it could take up to around 65 degrees to melt it completely. Also if using sodium acetate you have a second factor: solution must saturate which may require more heat. I would recommend adding an extra 10 degrees Celsius on to what you calculated for to make sure the water is in excess in the solution.

**The difficult part is knowing when the solution has fully melted. What to look for is to see if there are any parts of the liquid that look like ice, or even a needle.

Material used: solution in the beaker.
Suggested Equipment: beaker 250mL, Stirring rod, thermometer, heating device.

Option two: Here we will fill a water bath with enough water to cover most of the beaker. If the beaker starts to float you may hold it down so it will not tip over or place a heave Cleaned object to weigh down the beaker. With a water bath the solution will be a lot less likely to burn and the solution will melt everywhere the water covers. The time it will take to heat the water varies, but can take about ten minutes to get the water the same temperature as the heater. Heat the solution for about twenty minutes. when deciding whether the solution is ready or not place the thermometer in the solution not the water bath. If the temperature is above your calculated/recommended temperature then the solution is ready.

Material used: solution in the beaker, tap water.
Suggested Equipment: beaker 250mL, Stirring rod, thermometer, heating device, glass bowl.

## Step 7: Transferring the Solution to Clean Container

Step seven is an optional, but a strongly recommended step if you just completed option one because the heating device does cover the whole beaker. Here we will transfer the solution to a clean container while the solution is still hot (above 65 degrees Celsius). When pouring the solution make sure if any unmelted crystals that may have stuck to the beakers sides while melting do not fall in the new beaker. It is recommended that you briefly heat the solution again at the same temperature in step six for the the new beaker to make sure that there are no solid crystal formations left.

Material used: solution in the beaker.
Suggested Equipment: two beakers 250mL, Stirring rod, thermometer, heating device.

## Step 8: Cooling the Solution

Step eight is when we take the solution away from the heat source and allowed to cool to room temperature. This step takes about 30 minutes. At this step you may use a refrigerator to speed the cooling process. It is not advised to hover hand or touch the solution with a glove after this point to avoid contamination. Please note this is the step that will show if there was any solid formation of sodium acetate trihydrate left. Check on the solution once after ten minutes to make sure no crystals are forming*. After about 30 minutes the solution is ready for presentation, or may be stored for another day since it is a stable solution.

*If there are any crystals forming, that means there was an unmelted crystal that has touched the solution. The solution is still okay, it is a reversible reaction. Go back to step six and reheat the crystallizing solution. if it happens again try heating at a higher temperature. If the problem persists then try using option 2 for heating.

Material used: solution in the beaker.
Suggested Equipment: two beakers 250mL, refrigerator.

## Step 9: Presentation

Step nine is the step that is the step used for display. There are two common options used to display this super saturation phenomenon, however you may choose to be creative and make your own.

Few things to know before presenting:
1) When the reaction starts and the sodium acetate trihydrate changes phases from a liquid to a solid, the temperature will heat up to around 58 degrees Celsius. That is about how hot your tap water can get, most house hold have their water set at 52 degrees Celsius. This is not anything dangerous but can be unpleasant if touching while reaction is occurring.
2) The solution will not be set off by any disturbance, like touching the solution. Be cautious though because it is possible to set it off accidentally with any crystals still laying around.
3) The reaction does release energy, but most energy released is done so by temperature change.
4) This reaction has duration measured in seconds and milliseconds depending on the volume so plan accordingly.
5) Option two is not recommend if you had trouble cooling your solution because their may be crystals on the rim of the beaker.
6) If any part of the solution is above 58 degrees Celsius it will not change phases.

Option one: Have a seed crystal* on your finger tip, it just needs to be one. Push the seed crystal into the middle of the beaker so the reaction begins in the middle of the beaker. This display is done in seconds, but is great for taking good pictures.

*reminder seed crystal is the material sodium acetate trihydrate or sodium acetate that you used in the beginning.

option two: Have a seed crystal on a cleanable surface, it is recommended to use a petri dish because cleanup requires large amounts of water. place the seed crystal in the center of where you will be pouring your solution in the beaker. Begin pouring on the seed crystal slowly to get a base. Once the base has crystallized you may continue pouring making any type of crystal structure. The time of this reaction may be controlled by how fast you pour. The reaction is fast enough to clime a steady stream and start crystallizing the solution in the beaker. This display is great for demonstrations.

Material used: solution in the beaker.
Suggested Equipment: beakers 250mL, petri dish.

## Step 10: Clean Up

Step ten is cleanup after the presentation. Sodium acetate trihydrate is a non hazardous material and you may use may be disposed of the crystals or store them in general storage space. The disposal code for sodium acetate trihydrate is 26a meaning it can be disposed of in a landfill. For cleaning the remaining crystals on the surface the usual options are water, soap water, or acetone. Do not use strong oxidizers around the sodium acetate trihydrate. For sodium acetate trihydrate, which is the end product no mater what you used in the beginning, use tap water is best. Warm water will dilute the sodium acetate making the solution unsaturated. The unsaturated solution is a liquid and may be easily flushed out.

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