Experiment of the Effect of Different Dissolved Substances on the Rate of Ice Melting

3: Murriama and her friend, Sara, were enjoying their favourite ice blocks. Halima noticed that her ice block melted faster than Sara’s. She wondered why they melted at a different rate.

Q. Design and conduct an investigation to determine “if different dissolved substances impact the  rate at which ice melts”.

Possible requirements: Stopwatch [not necessary to purchase ice blocks to conduct this investigation).

PROBLEM SOLVING:

Introduction:

On a Saturday evening, in Detroit, the largest city in Michigan, United states, Murriama and Sara, two mutual best friends, were casually trying out their ice blocks from their favourite grocery store, Honey Bee La Colmena. Sara got hers, owned by a company called the House of Flavours, while Murriama got hers from Michigan’s favourite ice block brand, Dean’s Country Fresh Super Rainbow, Michigan’s favourite ice cream brand. While pleasantly enjoying their favourite ice blocks, Murriama noticed that the ice block she was having melted faster than that of Sara’s. She wondered why the melting occurred at a different rate. The reason why I have decided to work on this particular investigation is because I found the question to be very intriguing of a subject to research and conduct an investigation about. It also triggered my curiosity about why Murriama’s ice block melted faster than that of Sara’s. Henceforth, it was for the sole purpose of research and to investigate further into it in depth. This particular question can be tested by experimentation. Four weeks were provided for the completion of this student research project and it is initially possible for the question to be tested in the given time; design, conduct, analyse, construct etc. Throughout the experiment I performed, I determined that the addition of foreign, dissolved substances to ice does essentially impact the rate at which the ice melts, measuring time alongside. 

Aim:

The main aim of my extensive research project is to design and conduct an investigation which efficiently determines if different dissolved substances i.e. table salt (calcium chloride), raw sugar and/or sand (extracted/sampled/collected from Bondi Beach), impact the rate at which ice melts, within a constant temperature, under certain safe conditions. I will also initially measure the time it takes for each dissolved solution, in the ice cube to melt, using a stopwatch. Therefore, the aim is to observe the effects of dissolved substances e.g. table salt, raw sugar and sand against time, further impacting the rate at which ice melts by either increasing, decreasing or depressing the freezing point.

QUESTIONING AND PREDICTING:
Background Research:

• ¾ of the solutions used in this experiment are dissolves containing dissolved substances-

1. Salt
2. Sugar
3. Sand
4. (Distilled Water)

   No solute

• Pure distilled water has a melting/ freezing point of 0C (32F).
• Table salt and raw sugar are soluble substances and dissolve in water while sand does not dissolve in water.
• Experiments with ice cubes containing salt and sugar should show that cubes with sugar and salt melt faster than the cubes with only normal water. Initially, the ice cubes containing salt should melt faster than the cubes with the sugar solution. Valid reason= “heat absorption”.
• The salt or sugar in an ice cube absorbs the surrounding heat energy faster than frozen water itself. Due to salt and sugar absorbing heat so quickly, water molecules move faster, resulting in a faster melting rate.

-          (Linking to the real world=) This is part of the reason: cities extensively use salt to melt ice; salt absorbing heat energy quicker, thereby promoting increased rate of melting.

• Salt impacting the rate at which ice melts:

1. The ionic compound salt (sodium chloride- table salt) lowers the freezing point of the water  freezing point depression. The salt makes it harder for the water molecules to bond together in their rigid structure.
2. When a single molecule of salt dissolves, it breaks into two ions, a sodium ion and a chloride ion, thereby effectively doubling the ‘freeze blocking’ effect. [Calcium chloride is more effective/efficient at melting ice- break down into three ions instead of two: one calcium ion and two chloride ions.]

• Sugar impacting the rate at which ice melts:

1. Sugar lowers the freezing point of water by binding with the water molecules and creating more space between them. Hence, this helps them- overcome the electrostatic forces binding them into a solid structure.
2. When a molecule of sugar dissolves in water, we end up with a single molecule in solution. This extra molecule prevents water molecules from combining with ice crystals and freezing normally, thereby depressing the freezing point.

• Sand impacting the rate at which ice melts:

If heated naturally from the sun or a warm temperature, sand can melt just like all other substances which are at a higher temperature than ice. The actual texture of sand does not cause ice to melt. Sand, unless it is at a higher temperature than the ice, would not melt.

• Salt lowers the freezing point of ice by dissolving into a liquid water within the ice and lowering the freezing point from 0C to below 0.
• When using table salt will essentially dissolve into separate sodium ions and chloride ions.
• Sugar and salt melt ice by lowering water’s melting and freezing points.
• Normal tap water has already dissolved impurities or chemicals in it which will affect the rate at which ice melts- use of distilled water in my experiment.
• The total process of dissolution–decomposition into ions plus hydration–absorbs heat.

Hypothesis:

The hypothesis of my extensive study was that if there was a precedent change in the independent variables i.e. table salt, raw sugar, sand and distilled water, then there would be a predicted change in time, impacting the rate at which ice melts with observant levels of increased or decreased freezing points. My hypothesis also outlines that the salt solution will be the most impactful at affecting the rate at which the ice melts, rather than the rest of the solutions, with the solute sand being the least effective. Throughout the process of planning and investigating this research project, it is possible that this hypothesis can be tested by experimentation. By comparing the effect of the dissolved substances against time, measured in seconds, it would be possible to prove or disprove the drawn hypothesis and work on relevant regulation and conservation practices, determining if different dissolved substances do impact the rate at which ice melts.

PLANNING INVESTIGATIONS:

Risk Assessment: Risks:

• Breaking of glass equipment- create sharps that could essentially cut/ infect or introduce chemical or fluid into body.
• Spillage of water- create detrimental spills which have potential consequences of injuring a person. 
• Ingestion/ Consumption of solutes- sand salt, sugar- not meant to be ingested; experimental solutes and harmful for the body.
• Frost bite from being in contact with ice- cause numbness, pain or burning sensations to skin.
• Injury to self or others through the use of toothpicks- stab, poke etc. which leads to a physical injury or hazard.
• Contact with hot surfaces or equipment (e.g. stainless-steel pot): physical injuries i.e. burns etc. to self or others.  

State how I intend to minimise the risks:

• Breaking of glass equipment: wear PPE (personal protection equipment), use stable surface or use a holder.
• Spills (Water): Wipe the wet surface till it is dried up, prevent yourself or be cautious around any water spills or use a larger beaker.
• Ingestion/ Consumption of solutes: Preventing yourself or your peers from ingesting the solutes
• Frost bite: Wear gloves, use a holder or equipment to pick the ice up.
• The use of toothpicks/sharp objects: Wear protective hand wear, have a stable hold on toothpick whilst using.
• Contact with hot surfaces of equipment: Use kitchen mitts while handling hot objects etc., Use handle of the appliance, turn off switch and wait for the surface to cool down.

Experimental Variables:

Independent Variable (thing tested)= dissolved substances

1. Table salt (calcium chloride)
2. Raw Sugar
3. Sand (sample collected from Bondi Beach)

• Dependent Variable (thing measured)= Time for ice to melt
• Variables to be controlled (constants)=

1. Temperature [room temperature etc.]
2. Amount of solute [ ¼ tsps. each]
3. Amount of ice/ water [5ml]
4. Start time [7:20 pm]
5. Location of experiment [Living room etc.]
6. Person conducting the experiment (reaction time of humans vary; person to person)
7. The use of the same stopwatch throughout (the entire experiment)
8. Ice cube tray kept the same throughout the experiment 

• Control Group: Distilled Water [no solutes] (the independent variable which will not influence the results)

CONDUCTING INVESTIGATIONS:

Materials/ Equipment:

• 3× ¼ tsp/ 1.25 ml teaspoon (measuring spoon)
• 1× 50ml beaker/measuring cup
• 1× 1/4 tsp (1.25ml) of table salt (sodium chloride) [Brand: Woolworths. Himalayan Pink Fine Table Salt]
• 1× 1/4 tsp (1.25ml) of raw sugar [Brand: CSR. Raw Sugar]
• 1× 1/4 tsp (1.25ml) of sand [Extracted/sampled/collected from Bondi Beach]
• 3× Stopwatch [Brand: Casio]
• 1× Plastic Double-ended Toothpick pack
• 1× Refrigerator [Brand: Samsung]
• 1× Plastic Ice cube tray (28 cubicles) 
• 1× 3 to 5 gallon (11.4 to 19 litre) stainless-steel pot with a stainless-steel cover
• 1× Heat resistant glass bowl
• 1× Baking rack
• Ice (no solute) [for distilled water]

[∴ All equipment and materials that I have used in this experiment were easily obtained at low cost and from household items, whereas the sand was extracted from Bondi Beach, in the hopes of making this experiment accessible to perform/conduct and also to least worry about committing to plastic pollution when buying the sand from stores.

Why I have used distilled water instead of tap water: In order to conduct this experiment, I have used distilled water as one of my solutions/ control group/ replacement for tap water since tap water contains already-dissolved impurities and chemicals which might affect the initial rate at which the ice melts, making it complex for the experiment to be valid.]

Method:

1. Distilled Water:

1. Put the baking rack on the bottom of the stainless-steel pot.
2. Fill the pot halfway with tap water.
3. Place the glass bowl in the pot, so that it floats on the surface of the water. The baking rack should ensure that the bottom of the glass bowl doesn’t touch the pot.
4. Turn the pot cover upside down and place it on top of the pot.
5. Fill the inverted pot cover with ice.
6. Bring the water to a boil and let it boil for about 30-45 minutes.
7. Wait for the condensed water to cool down.
8. Repeat steps 1-7 to acquire the correct measurement of a 100 ml. 

2. Initial Method:

(The following steps were repeated 2 more times for reliability and to give a total of each replicate, with the solutions in the same ice cube tray: )

1. Pour cooled distilled water into the 50ml beaker/measuring cup and measure 5ml of water for each cubicle.
2. Add 5ml (1 TSP) of distilled water to each 15 ice cubicles of the ice tray; 3 for table salt (sodium chloride), 3 for raw sugar, 3 for sand and 6 for distilled water only (no solution).
3. Measure ¼ tsp of salt, sugar and sand using three ¼ teaspoons.
4. Add the measured ¼ tsp of sand, salt and sugar in each of the filled-up cubicles of the ice cube tray; 3 for sugar, 3 for salt and 3 for sand.
5. Dissolve/ mix each solution with toothpicks.
6. Put them in the refrigerator and wait for an estimated 3-4 hours for the ice to melt.
7. Take the ice cube tray out of the refrigerator and prepare to use the stopwatches.
8. Start your timer on each of the stopwatches together and write down the starting time.
9. Observe each of the four ice cubes with dissolved salt, sand, sugar and the ice cube with distilled water only and wait for them to completely melt.
10. Poke around with a toothpick to check up on the progress of the ice cubes during the process of melting.
11. Stop a stopwatch and write down the end time when the first ice cube completely melts.
12. Repeat the same steps for the other three solutions and also another two times using the rest of the frozen solution left in the ice cube tray, further testing for reliability.
13. Conduct this experiment independently since reaction times of humans may vary and in the same, constant room to ensure that temperature remains constant.

PROCESSING AND ANALYSING DATA

Results: 

SALT solution

SUGAR solution

SAND solution

DISTILLED WATER (ONLY)

Figure 1: Before dissolving the solutes in the distilled water; table salt, raw sugar and sand.

SALT solution

SUGAR solution

SAND solution

DISTILLED WATER ONLY

Figure 2: After dissolving the solutes in the distilled water; dissolved substances: table salt, raw sugar and sand.

SALT solution

SUGAR solution

SAND solution

DISSOLVED WATER ONLY

Figure 3: The solutions have been frozen in the refrigerator for an approximate of 3½ hours at a temperature of 38 F (3.3C).

First Trial                         [Friday, 6^th September. 2019 7:20 pm]

SAND: Took 5400 sec (1 hr 30 mins) to successfully melt.

DISTILLED WATER ONLY: Took 6000 sec (1 hr 40 min) to successfully melt.

SALT: Took 300 sec (5 mins) to successfully melt.

SUGAR: Took 3300 sec (55 mins) to successfully melt.  melt.

Second Trial                   [Saturday, 7^th September 2019 7:20 pm]

SALT: Took 480 sec (8 mins) to successfully melt.

SAND: Took 5700 sec (1 hr 35 mins) to successfully melt.

DISTILLED WATER ONLY: Took 6600 sec (1 hr 50 min) to successfully melt.

SUGAR: Took 3720 sec (1 hr 2 mins) to successfully melt.  melt.

Third Trial                   [Sunday, 8^th September 2019 7:20 pm]

…..

SALT: Took 900 sec (15 mins) to successfully melt.

DISTILLED WATER ONLY: Took 7200 sec (2 hrs) to successfully melt.

SAND: Took 6120 sec (1 hr 42 mins) to successfully melt.

SUGAR: Took 4080 sec (1 hr 8 mins) to successfully melt.

∴The following table above states a simple perspicuous explanation that dissolved substances do indeed impact the rate at which ice melts. For the first trial performed, it is visible that salt had the most impact on the ice melting, resulting in  a  faster rate of the ice melting, whereas the solution with sand and distilled water only had the least impact on the ice melting, resulting to a decreased rate of the melting of the ice.  

∴Compared to the first trial, the second trial has also very similar results with the salt solution being the first to melt followed by sugar, sand and then the solution with distilled water only (no solutes). Furthermore, it also highlights how these dissolved substances impacted the rate at which the ice melted, with some efficiently depressing the freezing point at a fast rate. 

∴The following table above emphasises on the context of how dissolved substances impact the rate at which ice melts. With a comparison with the other trials, the third trial also states that salt aids in melting ice the fastest followed by sugar. The least reactive dissolved substances that impact the rate at which ice melts include sand etc., further proving how dissolved substances i.e. table salt, raw sugar, sand etc. impact the rate at which ice melts, either by lowering the freezing point or increasing the rate of ice melting.

Final Table(s):

Discussion:

The initial experiment results outline that dissolved substances i.e. table salt, raw sugar, sand etc. along with the controlled group, distilled water, do indeed impact the rate at which ice melts, also signifying the consequential occurrences of low freezing points. Throughout the conduction of three trials in my experiment, it is observant that dissolved substances play an impactful role when it comes to making ice melt, especially salt, sugar and sand. Prior to the results for all the three trials, it is visible that salt is the most effective and melts the ice cube the fastest. This is because this ionic compound lowers the freezing point of the water/ freezing point depression making it harder for the water molecules to bond together in their rigid structure eventually forcing the water molecules to move faster, resulting at a faster melting rate. When a single molecule of salt dissolves, it breaks into two ions, a sodium ion and a chloride ion, thereby effectively doubling the ‘freeze blocking’ effect, alongside melting ice the fastest compared to the controlled group, distilled water, and the other solutes, sugar and sand. [Salt initially took 560 seconds (mean time) to melt.]

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Sugar is also one of the solutes which absorbs the surrounding heat energy the fastest than the control group, distilled water, and the rest of the solutes, except salt. Sugar lowers the freezing point of water by binding with the water molecules and creating more space between them. Hence, this helps them overcome the electrostatic forces binding them into a solid structure. When a molecule of sugar dissolves in water, we end up with a single molecule in solution. This extra molecule prevents water molecules from combining with ice crystals and freezing normally, thereby depressing the freezing point. [Sugar initially took 3700 seconds (mean time) to melt].

However, the solute sand does not melt ice any faster than salt or sugar. This is because the actual texture of the sand does not cause the ice to melt. If heated naturally from the sun or a warm temperature, sand can melt just like all other substances which are at a higher temperature than ice. Sand, unless it is at a higher temperature than the ice, would not melt. [Sand initially took 5740 seconds (mean time) to melt].

Furthermore, through observing the three trials, it is visible that the ice cube containing only distilled water, was the least effective at melting ice the fastest, further determining that the “different” dissolved substances i.e. salt, sugar and sand, effectively impact the rate at which ice melts on a diverse spectrum. Furthermore, when compared to the controlled group, distilled water, it is shown that the ice cube containing distilled water only was least effective at impacting the initial rate at which the ice cubes melted. [Distilled water initially took 6600 seconds (mean time) to melt].

In the experiment conducted, there are some strengths and weaknesses. The following identified are as follows:

• Strengths:

-          There is a tighter control of variables, making it easier to comment on cause and effect.

-          Utilised accessible, household and cheap items for equipment.

-          The experiment is relatively easier to replicate.

-          It is also cheaper and less time-consuming than other methods.

-          Not a subject to human error if tried for reliability for a duration of more than three times.

• Weaknesses:

-          The experiment demands more characteristics – the participants aware of experiment, may change their behaviour.

-          The experiment conducted had low ecological validity making it difficult to generalise to other situations.

-          There were few experimenter effects, may be bias when experimenter’s expectations affect behaviour.

-          (Where the experiment was conducted: artificial environment- implying that there was low realism.)

-          (Subject to human error if not tried more than three times.)

Some future improvements that could be proposed for this experiment to be more effective are as follows:

-          Making repeated measurements in order to eliminate error in  measuring i.e. measurement of water, solutes etc.

-          Increasing the sample size of solutes or perhaps a bigger ice cube tray/ amount of water etc.

-          Introduction of more independent variables; the solutes, in order to highlight an even diverse range of dissolved substances and how those affect the initial rate at which the ice melts.

-          Repeating the experiment a few more than three times in order to strengthen reliability.

Ideas for future investigations proposed:

Some ideas for future investigations could include an investigation with different solutes or different solvents. Furthermore, they could also include/utilise the same solutes, but conducted at different temperatures. There could also be an entirely different experiment with different solutes, solvents etc. and in a different format.

This investigation can also be efficiently linked to the real world. During winter, many cities and municipalities, across the world, extensively depend on salt, especially rock salt, in order to de-ice their roadways when the weather gets bad. This process runs through the analogy of road salt works lowering the freezing point of water via freezing point depression. The freezing point of the water is lowered once the salt is added, so it the salt makes it more difficult for the water to freeze. Henceforth, this investigation determines how dissolved substances may affect the rate at which ice melts, also interlinking this to a real-life scenario occurring and how some dissolved substances are more effective than others. 

Conclusion: 

The initially drawn hypothesis that dissolved substances impact the rate at which ice melts, especially amongst the three solutes; table salt (sodium chloride), raw sugar and sand, and the solution with only distilled water, where salt is the most efficient at melting ice and sand being the least effective, is supported by the results. In the experiment conducted, it has been made clear on how salt had melted ice the fastest, followed by sugar whilst having sand and the controlled group, distilled water, to be the least effective at melting ice the fastest. This helps outline and support the main aim of this investigation task and further convey the context of observing the effects of table salt, raw sugar and sand against time and how it may impact on how the ice melts via freezing point depression. However, the analytical results identified indicates a rejection of hypothesis where it states how the solute sand will take the longest to melt. The results support otherwise, outlining that the solution with only distilled water takes the longest to melt.

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