Flames, heat, and calories Lab report

Introduction 

Visualizing a good model of heat or energy is tiresome.  Sometimes heat can be perceived in what it does.  Scholars believed that when water is heated, its molecules move at faster velocities and collide with the molecules next to them faster. Hence, visualizing energy at molecular stage aids in coming up with a reasonable model of understanding the energy or heat fully.  For instance, water exists in two forms (solid and water). Therefore, their molecular behavior must be different.  A good model for water will be that which accounts for the changes that take place when it is changing from one form to another. As water liquid converts to solid, much of the energy associated with its molecules is lost. The loss of the energy makes the frequency of the movement and collision of molecules to reduce. When melting solid water (ice) by increasing the quantity of heat, some of the added heat to ice, breaks the attraction forces that hold water molecules together.  The heat that is needed to convert one gram of ice into liquid water is referred to as heat of fusion. During chemical reactions, heat is released or absorbed depending on whether the chemical bonds in the substance are broken or formed.  When a bond is broken, it often cost energy and also the formation of the chemical bonds needs energy. The energy of bond formation or bond breaking depends on the relative energy of the bonds.  Every substance requires a specific and measurable quantity of energy to change its temperature by a given amount. Specific heat is the amount of energy in calories needed to increase the temperature of one gram of an element or a compound by one degree centigrade.  Flame, heat, and calories find use in the OSHA and FR clothing (Paraventi 2012).

The purposes of this experiment were to; explore the concept of heat and calories, heat gain, heat loss, compare the chemical and physical energy changes. The last objective was to obtain the amount of energy produced by burning peanut.

Procedure

Heat loss and heat gain were carried as follows: the mass of Styrofoam cup (2.308 grams) was weighed and then amount cold water was poured into it. The weight of the cold water together with the Styrofoam cup (37.112 grams) was measured. Hot water was placed in another Thermo Cup, and the temperatures of cold and hot water were taken.  Then hot water was poured into cold water and then followed by inserting the temperature sensor into the mixture. The temperature of the cold and hot mixture was taken when it was relatively stable.  The weight of the mixture was then recorded and the weight of added hot water obtained by subtraction. Heat released during the chemical change was performed by; weighing the candle and  piece of the towel together, followed by putting the candle on a piece of the towel below the metal cup(the cup contained 100ml of water).  The height of the cup was then adjusted to 1 inch above the wick of the candle.  The temperature of the water inside the cup was taken. After the molten candle wax had been allowed to cool, the weights of the candle were measured to aid in getting the amount of burned candle. The procedure for heat evolved during the chemical reaction was repeated by replacing the candle with the peanut. 

The heat released as the result of the physical change was determined by; weighing Styrofoam cup and adding warm water into it, followed by measuring the weight of the cup and its contents. The temperature sensor was inserted into the cup and the temperature taking begun. One-third of 50ml-beaker of was added inside the cup containing warm water. Then the temperature of the mixture was monitored while stirring the mixture with the thermometer sensor.  The specific heat of the metal (brass) was performed by taking the weight of the Styrofoam cup, cold water, and the cup. The temperature of brass was taken before it was transferred inside the cup containing cold and after it was moved. 

Discussion

When cold water and hot are mixed, the expectant temperature will be of uniform temperature between hot and cold water temperature extremes. According to the molecular model, hot water molecules move at faster and collide with cold water frequently. In the mixture of cold and hot water, a given amount of energy is transferred from hot water molecules to cold water molecules. This energy is calculated in the form of heat.  For example, cold water gained was 454.286 calories while the hot water lost was 482.36 calories.

During the burning of the candle, the quantity of heat evolved was the same as the amount of heat absorbed by water. In this experiment, the amount of heat given off by one gram of burning candle was 2300.76 calories. This quantity of heat liberated by one gram of candle represents the heating capability of the candle, and it is the measure of the chemical reactions taking place during the burning of the candle.  The amount of heat given off by one gram of peanut was 4485.17 calories. Heat produced by one gram of peanut was higher than heat produced by one gram of the candle by nearly by a half (2184.41 grams).

The quantity of heat consumed by solid water (ice) is the same as the amount of heat given off by the hot water.  The heat absorbed by solid water has two components. For instance, the quantity needed to convert the ice to liquid water at 0 degree Celsius and the final temperature achieved by the sample.  The heat energy between heat lost by hot water and the heat absorbed by the melted ice is the heat used in melting the ice. Therefore, the one gram of heat needed to melt ice was 73.506 calories, and it was the heat fusion.

For this experiment, the value of heat (73.506 calories) required to convert one gram of ice into liquid was inconsistent with what is in literature (79.7 calories). Hence, the heat of fusion value was not reasonably close to the accepted value. The specific heat capacity of brass (0.104J/g degree Celsius ) was inconsistent with the accepted value (0.380J/g degree Celsius) with a percentage error of 72.63%. The heat loss to the environment associated with the methods contributed to the errors related to the experiment.  

Conclusion

The energy absorbed by cold water was less than the total amount of heat given off by the hot water. Therefore, there was heat loss to the surrounding. The heating ability of peanut was better than that of burning candle. Hence, when other factors are considered peanut should be applied in heating.  The heat energy produced due to chemical change was higher than heat released as the effect of physical changes.  The insulation of the Styrofoam cup during experiment should be done to minimize the heat loss to the surrounding.  

References

Paraventi, M. (2012). OSHA & FR clothing: How to minimize arc flash injuries. ISHN, 46(1), 36-37. Retrieved from http://search.proquest.com/docview/919624160?accountid=