Designing an Efficient Hand Warmer
February 6, 2016 - March 19, 2016
The background behind the project was to create a product that students will buy if they are cold at a sporting event. Due to the cold weather, there would need to be an increase in temperature and it should last as long as possible. This product also incorporated techniques to appeal to a market; part of the challenge was to make the hand warmer profitable, comfortable, and easy for consumer use. More scientific aspects my group was concerned with was achieving a sufficient increase of temperature and using salt solutions safely. The process our group went through was to first discover a successful product and then refine our design to appeal to potential costumers.
Background Experiments:
In order to learn about temperature change, we conducted several experiments involving reactions between salts and water. Through these tests, we studied the formula for energy, different types of reactions, and specific heat capacity. The first experiment included using calorimetry-- the technique of using an insulated container to measure the enthalpy of a reaction. We measured out five grams of magnesium sulfate and dissolved it into twenty-five milliliters of water. We compared the initial heat of the water at room temperature to the peak in the temperature once the salt was added. This temperature change can be used in a formula, q=mcΔT, to calculate the energy in Joules (The data can be found in the spreadsheet below).
Energy Calculation Example: |
q = mcΔT |
ΔT = 57.6 - 20.3 = 37.3 *C
q = (6.02 g)(4.178 J/g*C)(37.3 *C) q = 938.15 Joules
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q represents energy [Joules]
m represents the mass of solute (in this case salt) [grams] c represents the specific heat capacity of the solvent [Joules/grams x degrees Celsius] ΔT represents the change of temperature [degrees Celsius] |
Enthalpy and Entropy:
One of the most important topics covered through this project was the ability to track the flow of energy in a reaction, both in the system and in the surrounding environment. Enthalpy is known as the total amount of energy in both the reaction and environment. This means it includes temperature, pressure, and volume. If a reaction gives off heat, that means the enthalpy in the system is negative because the energy in the surroundings increases. Entropy is chaos or disorder. This can be thought of as the activeness and movement of particles in the system. When an object is cold, the molecules are tightly packed together and are moving slowly. Therefore, it would have a low entropy. On the other hand, if an object is heated, like a gas, the molecules are speedily bouncing around and are not as contained. This means gases have a higher entropy. Through critical reasoning, it can be concluded that if heat is added to a system then the entropy increases and the particles move faster.
Endothermic Versus Exothermic:
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Another crucial aspect to understand in reactions was the difference between endothermic and exothermic. In order to create a successful hand warmer, heat needs to be released. This means that an exothermic reaction was desired. Cross applying, this also means that our desired reaction should also have an increase in entropy and the enthalpy should also be negative. Exothermic reactions are also considered spontaneous, which means that extra energy is not needed in order for the reaction to reach the activation level. This is why most reactions found in nature tend to be exothermic.
Endothermic reactions are the complete opposite. This reaction requires external energy to begin and the final products ends up with less energy than the start. It would feel cold to the touch and is not considered spontaneous. These reactions have a positive enthalpy because the system is absorbing energy from the environment. Since the overall energy in the reaction is less, that means the substance cooled and therefore the molecules move slower and the reaction has low entropy. |
Specific Heat Capacity:
Specific heat refers to the amount of energy needed to increase the temperature of a substance by one degree Celsius. The higher a specific heat, the more time it will take to heat up a solution. This also means it will take more time for the solution to lose heat. Therefore, an ideal product for a hand warmer would be a substance with a high specific heat, such as water. Although it may take more effort to initially heat up the water, the hand warmer will be able to retain this heat. Air is the base line for specific heat capacities with a measurement of 1 Joule per grams times degrees Celsius. The specific heat capacity is used in the q=mcΔT formula.
Ionic and Covalent Bonds:
Ionic bonds are when molecules are broken apart into cations and anions. Each ion is surrounded separately by water molecules. The highly negative oxygens are attracted to the cations and the highly positive hydrogen is attracted to the anions. Due to these attractions, when salts are added to water, the bonds in the salt are broken and the ions are kept apart by the polar water molecules. This is the type of bonding in the reaction between Lithium chloride and water is an example of an ionic bond forming. Covalent bonds are when individual molecules separate and the entire molecule becomes surrounded by water. Between two molecules, not including water, the bond will form through electron sharing. Generally, these bonds are stronger than ionic bonds, but there is no definitive answer because the strength of the bond depends on the atoms involved.
Reflection:
During this project there were both positive and negative proceedings. Regardless, I was able to learn from these mistakes or successes and I will be able to apply this knowledge to improve future work.
The most challenging and diverse aspect of this project was the objective to market our product and actively try to sell it to consumers. I think that my group fell short of demonstrating the success of our product during our presentation. I think it would have helped to present to classmates beforehand and receive feedback. In the future, I will try to gain peer critique regardless of what the class schedule is like. Spending time outside of class revising the presentation points would be beneficial to the marketing aspect.
The most stressful challenge my group faced was the spontaneous disappearance of the type of bag we were using. After creating a working model, my group focused on our presentation and then, two days before the presentation, decided to construct several products. Unfortunately, the miniature ziplock bags were gone and we had to present the following week. Luckily another group was willing to switch spots with us so we were able to construct last minute tiny bags. This issue taught me to double check the model with enough time in case alterations need to be made.
One of the peaks of the project was my group's decision for the finalized product. After managing to create one successful hand warmer, we stuck with the initial concept of the method of mixing the contents and the substances we used. This strategy allowed my group to perfect our design and spend more time working on the proposal and marketing points. I learned from this experience that it is more important to emphasize the value of a product and project that to the audience than to create the most ideal design. This holds true because there are shortcomings to all manufactured goods.
Finally, another positive aspect of this project was the strong collaboration of my group. Despite some members being distracted at times by homework from other classes, everyone still contributed moth ideas and physical work. We were able to divide the work for testing our models and creating the slideshow so that everyone could be involved in both processes. I think this aspect was crucial to our success because it allowed all of my group members to become experts in both the manufacturing decisions and the layout of the presentation. This helped us hold a more professional attitude because direct involvement causes the most memories and excitement when trying to portray a concept to an outside audience.
The most challenging and diverse aspect of this project was the objective to market our product and actively try to sell it to consumers. I think that my group fell short of demonstrating the success of our product during our presentation. I think it would have helped to present to classmates beforehand and receive feedback. In the future, I will try to gain peer critique regardless of what the class schedule is like. Spending time outside of class revising the presentation points would be beneficial to the marketing aspect.
The most stressful challenge my group faced was the spontaneous disappearance of the type of bag we were using. After creating a working model, my group focused on our presentation and then, two days before the presentation, decided to construct several products. Unfortunately, the miniature ziplock bags were gone and we had to present the following week. Luckily another group was willing to switch spots with us so we were able to construct last minute tiny bags. This issue taught me to double check the model with enough time in case alterations need to be made.
One of the peaks of the project was my group's decision for the finalized product. After managing to create one successful hand warmer, we stuck with the initial concept of the method of mixing the contents and the substances we used. This strategy allowed my group to perfect our design and spend more time working on the proposal and marketing points. I learned from this experience that it is more important to emphasize the value of a product and project that to the audience than to create the most ideal design. This holds true because there are shortcomings to all manufactured goods.
Finally, another positive aspect of this project was the strong collaboration of my group. Despite some members being distracted at times by homework from other classes, everyone still contributed moth ideas and physical work. We were able to divide the work for testing our models and creating the slideshow so that everyone could be involved in both processes. I think this aspect was crucial to our success because it allowed all of my group members to become experts in both the manufacturing decisions and the layout of the presentation. This helped us hold a more professional attitude because direct involvement causes the most memories and excitement when trying to portray a concept to an outside audience.