Experiment 6

Experiment 6: Heat Effects Renoir Del Mundo, Maja Rael Del Villar, Jerald Joseph Domingo, Kristella Draheim 3-BIO 3 College of Science, University of Santo Tomas España, Manila Philippines Abstract The heat effects of an object to its nature can be identified and calculated by different aspects that will give us our desired values. In this experiment, we use different application methods such as identifying the specific heat of a metal, observing the heat of fusion of water, and determining the coefficient of linear thermal expansion of solid. The accepted value of specific heat in metal in the first activity is measured 452 and the group gathered around 433.26 to be exact. In the second activity, the calculated latent of heat fusion is 1.3x103j/kg. And for the third activity the accepted value of coefficient of thermal expansion is 2.3x10-5. This experiment, getting the temperature is the core and it can’t be done with the use of thermometer. We also calculated the percent error of each activity to further know how close are we to the true value. 1. Introduction The specific heat (also called specific heat capacity) is the amount of heat required to change a unit mass (or unit

quantity, such as mole) of a substance by one degree in temperature. Therefore, unlike the extensive variable heat capacity, which depends on the quantity of material, specific heat is an

intensive variable and has units of energy per mass per degree, or energy per number of moles per degree (O’Hanian, H.C., 1985). In this first activity, using the calorimeter and thermometer does identifying the specific heat of metal submerged in hot water. The calorimeter is an object used for calorimetry. Calorimetry is defined as the science associated with determining the changes in energy of a system by measuring the heat exchanged with the surroundings. The value accepted for this activity is 452. In the second activity, we determine the latent heat of fusion and latent heat of vaporization of water. Heat of fusion is identified, as the energy required

changing a gram of a substance from the solid to the liquid state without changing its temperature. This energy breaks down the solid bonds, but leaves a significant amount of energy associated with the intermolecular forces of the liquid state. The group again used the calorimeter as the vessel for ice and water used in this activity. The group measured the heat of fusion of ice when the ice finally melted and is fused with the initial water in the calorimeter and is now so called thermal equilibrium. And the calculated latent heat of fusion in this activity is 1.3x103 j/kg.

In the last activity for this experiment, the group determines the coefficient of linear thermal expansion of solid. Expansion of solid when heated can be explained as all materials (solids, liquids and gases) expand as they become warmer. In the case of solids, the atoms vibrate more as the temperature goes up. So, even though they stay joined together, they move slightly further apart, and the solid expands a little in all directions. It is very difficult to prevent the thermal expansion of solids and liquids, as the material will create very large forces if it is not allowed to expand. The accepted value of coefficient of thermal expansion for this experiment should be 2.3x10-5. 2. Theory

It is said that the length of an object changes when the temperature changes. ΔL = αLoΔT The equation shows the change in length (ΔL) that is the result of the coefficient of thermal expansion (α) multiplied with the initial length (Lo) and the change in temperature (ΔT). The common unit for the coefficient of linear expansion: 1 =(℃)−1 ℃ In the volume thermal expansion, the volume of an object changes when the temperature changes. ∆ V = βVο ΔT The equation shows the change in volume ( ∆ V ¿ is the result of the coefficient of volume expansion ( β ¿ multiplied with the initial volume (V o) and change in temperature ( ∆ T ¿ . The common unit for the coefficient of volume expansion: 1 (℃) ℃

-1

The heat must be supplied or remove to change the temperature of an object. That is

Q=mc ∆ T

3. Methodology The experiment was conducted at room 303, Main building, UST. The following materials and tools were used: calorimeter, hot plate, thermometer, ice, metal object, thread, metal jacket, beaker, linear expansion apparatus, boiler, meterstick Activity 1: Specific Heat of Metal The following were pre-weighed: inner vessel of the calorimeter and inner vessel with 2/3 water. Temperature of inner vessel was measured using a thermometer. A long thread was attached to the metal object. The object was place in a beaker. The beaker then was heated until the temperature reached 80°C. The object is quickly transferred to the calorimeter and covered and final temperature was taken note. Specific heat of the metal object was computed, as well as the % error.

Inner vessel of calorimeter inner vessel filled with water were weighed. Initial temperature determined after placing vessel insulating jacket.

and prewas into

Pieces of ice were added into the inside of the calorimeter. Stirred with a thermometer until all ice were melted. Final temperature was recorded. Inner vessel with ice was measured followed by the computation of Heat of fusion of ice by conservation of heat energy and % error. Activity 3: Thermal Expansion of Solids The initial length of rod was measured with means of a meter stick and the micrometer attached to the rod. One end of the rod was left free to expand while the other locked. One end of the rubber tubing was connected to the jacket and the other end to the boiler. The initial temperature of the rod was measured by inserting a thermometer into the central hole, touching the rod. The rod was heated by means of steam coming from the boiler. Final temperature of the rod was recorded after 20mins of heating using the micrometer. With the use of the collected measurement, coefficient of linear thermal expansion was computed followed by % error.

Fig1. Calorimeter

Activity 2: Heat of Fusion of Water

Fig 2. Set up for Activity 3

4. Results and Discussion The group conducts experiment about the effects of heat in solid and liquid phase. With the use of metals and water, the group determined the amount of heat transfer in a system. Table 1: Specific Heat of Metal Mass of sample 0.017kg Mass of inner vessel 0.04 kg of calorimeter Mass of inner vessel 0.19 kg of calorimeter with water Mass of water inside 0.14 kg inner vessel of calorimeter Initial temperature of 27o C water and inner vessel of calorimeter Temperature of 80oC sample Equilibrium temperature of 28oC sample, water and inner vessel of calorimeter Calculated specific 433.26 heat of sample Accepted value of 452 specific heat 4% % error Table 1 shows the results of specific heat of metal. The metal has an 80oC which is the amount of temperature that transfer from boiling water. 1oC is the amount of temperature that transfers by metal to

calorimeter. 452 are the amount of heat requires raising the temperature in one degree Celsius. The possible source of error is there might have been significant heat loss to the surrounding while transferring the hot sample from the beaker into the calorimeter and this heat loss might affect the values and results. Table 2: Heat of fusion of water Mass of inner vessel 0.0574 kg of calorimeter Mass of inner vessel 0.196 kg of calorimeter with water Mass of water inside 0.1386 kg inner vessel of calorimeter Mass of melted ice 0.1636 kg Initial temperature of 30oC water and inner vessel of calorimeter Equilibrium temperature of inner vessel of 16oC calorimeter, water and melted ice Calculated latent 1.3 x 105 j/kg heat of fusion Accepted value of 33.5 x 104 j/kg latent heat of fusion % error 61% Table 2 shows the results of heat of fusion of water. 30oC is the temperature of water inside the calorimeter and 0oC is the temperature of ice. 1.3 x 105 j/kg is the latent heat of fusion requires melting the ice and fusing in water. The possible source of error is the unbalance amount of water and ice because it takes a lot of

energy to melt the ice if the amount of ice is higher than water. And if the water is too high the energy that exerts to melt the ice will be increase. Table 3: Thermal Expansion of solids Initial length of rod 550 mm Initial reading of 0.4 mm micrometer disc Final reading of 1.2 mm micrometer disc Elongation of rod 0.8 mm Initial temperature of 24oC rod Final temperature of 94oC rod Experimental value of coefficient of 2.1 x 10-4 thermal expansion Accepted value of coefficient of 2.3 x 10-5 thermal expansion % error 8% Table 3 shows the result of thermal expansion of solids. 24oC is the temperature of rod in 0.4 mm reading of micrometer. After heating, the temperature of rod rose to 940C so the rod elongates from 0.4mm to 0.8mm. 2.1 x 10-4 is the coefficient of thermal expansion. 5. Conclusion: In activity 1, it has been shown that the specific heat of a solid by method of mixtures can be determined. The specific heat of the metal was computed using energy conservation. By knowing the specific heat of water and calorimeter, their masses, and corresponding changes

in temperature, the specific heat of the metal is known because of this principle: Qlost, metal = Qgained, water + Qgained, calorimeter. In the table, the calculated specific heat of the metal is 433.26 J/kgC which has a 4% error as compared to the accepted value of 452. In activity 2, the group determined the latent heat of fusion and latent heat of vaporization of water. The latent heat of vaporization of water is greater than its heat of fusion. When the ice was heated into liquid, the kinetic energy of its molecules increased making the forces of attraction reduced. While in vaporization, heating a liquid into a gaseous state, the kinetic energy increased to a point where there are no forces of attraction between the molecules. However, it is only the heat of fusion of ice that was computed by conservation of heat energy. In the table, the calculated latent heat of fusion is 1.3 x 105 J/kg which has a big percentage of error comprising 61% as compared to the accepted value of 33.5 x 10 4 J/kg. In activity 3, thermal expansion of solids has been demonstrated by the group. The coefficient of linear thermal expansion of the rod was computed by knowing the change in length per unit length and per unit change in temperature, having the value of 2.1 x 10-4 which has an 8% error as compared to the accepted value of 2.3 x 10-5. 6. Application: 1. It is possible to add heat to a body without changing its temperature. This happens during a phase change that requires

energy. When a state changes from one to another, the change is called the latent heat. This allows the object to absorb heat energy without increasing the temperature. 2. Steam burns are more painful than boiling water burns because the latter has high latent heat of vaporation. Thus, steam holds much more energy. If you put your hand in a steam, it condenses back to water and cools. Consequently, your hand absorbs not only the heat from the water but also from the latent heat.

bottle if you find it difficult to remove the stopper. The bottle would expand and the stopper comes out easily. However, it can cause as a nuisance to man. An example is when there are surface defects and patholes on the road due to continuous excessive expansion in the morning and contraction at night. There would be an expensive cost in the engineer design for reconstruction. Roadway must be poured into sections or gaps to accommodate these expansions. 7. Reference

3. Early in the morning when the sand in the beach is already hot, the water is still cold. But at night, the sand is cold while the water is still warm. This is because a body absorbs and releases heat depending on the surface area. Since, the ocean has a bigger surface area than the sand, it requires more time to absorb or release the heat. 4. Alcohol rub is effective in reducing fever because its cooling effect on skin employs an immediate home ready. As the alcohol evaporates, it carries the heat away from the body with it. Although, too much of isopropyl alcohol may lead to hazardous cases or may have side effects. 5. Thermal expansion has advantages and disadvantages to humanity. Practical examples would be heating the neck of the

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