Calorimetry and Specific Heat Abstract

Calorimetryand Specific Heat

Abstract

Thisexperimental report focuses on a calorimetry experiment done toobtain the specific heat of an unknown metal sample. The methodemployed the use of a water calorimeter to determine the specificheat. The principle behind the experiment was that the heat lost bythe metal sample is equivalent to the heat gained by water. Usingthis notion and the readings obtained from the experiment, thespecific heat of the metal was calculated, and the experimental valuewas close to the literature value for lead metal.

Problem

Thescience that deals with the dimension of the quantity of heat isknown as Calorimetry. This heat is generated by the kinetic motion ofatoms and molecules within a compound. The conflicting terms in thisexperiment are heat and temperature. The temperature of a substanceis usually constant regardless of the mass it has. The quantity ofheat, on the other hand, differs between similar substances that havedifferent masses. The unit that is used for temperature is theCelsius and is denoted as degrees. Heat quantity, on the other hand,uses energy standards such as calories and joules. The specific heatis the measurement that unites temperature and quantity of heat. Thespecific heat is defined as the amount of heat needed to raise onegram of a compound through a degree of temperature (Beran, 43). Themathematical equation that expresses these three terms is shownbelow.

q= m x spht x Δ0C

Where:

qis the amount of heat measured in joules or calories

mis the mass of the substance in grams or kilograms

sphtis the specific heat of the substance

Δ0Cis the temperature change in degree Celsius

Thespecific heat of a substance is usually constant. For water, it isone calorie that is equivalent to 4.184J/g 0C. The higher thespecific heat of a compound, the more amount of heat is needed toraise its temperature. If the specific heat is known, the heatquantity can be easily determined since the other measurements can beeasily obtained in a laboratory (Slowinski et al., 2015).

Thefollowing experiment tried to determine the specific heat of metalusing the amount of heat lost by the metal sample and the amount ofheat gained by water.

Hypothesis

Todetermine the experimental specific heat of an unknown metal sample.

Materials

Styrofoamcups, thermometers, metal samples, test tubes with a diameter ofabout 22mm, Bunsen burner, wire gauze, 400ml beaker and a 4”cardboard square with a hole at the center for supporting thethermometer.

Procedure

Adry metal sample was weighed, and its weight was recorded.

Thesample was carefully slid into a dry test tube, and a thermometer wasplaced alongside it.

Thetest tube was attached to a stand and then it was placed into a 400mlbeaker. Tap water was poured into the beaker till the level was about2 inches higher than the metal. Cautioned was maintained to ensurethat the test tube and its contents remain dry. The water in thebeaker was heated to boiling point and maintained for about fiveminutes.

TwoStyrofoam cups were nested together, and their weight was measuredand recorded. Cold de-ionized water was poured about halfway into thenested cups, and the new weight of the cups plus water was obtainedand recorded.

Thefinal temperature that the metal sample reached was read andrecorded. The original temperature of the water in the calorimeterwas also read and recorded.

Themetal sample was then dropped into the Styrofoam cups and left tostand for about five minutes. After this, the final temperature wasmeasured and recorded.

Results

Trial 1

Trial 2

Mass of metal sample (g)

54.95

54.95

Mass of calorimeter (g)

3.84

4.18

Mass of calorimeter + water (g)

164.86

159.55

Initial water temperature (0C)

19.3

19.9

Temperature of heated metal (0C)

91.2

94.0

Final temperature of metal + water (0C)

20.7

20.1

Analysis

Trial1

Themass of water &shy= mass of water and calorimeter – mass ofcalorimeter = (164.86-3.84)

=161.02g

Changein temperature of water = final temperature of metal and water –initial temperature of water = (20.7-19.3) 0C = 1.40C

Changein temperature of metal = final temperature of metal and water –temperature of heated metal = (20.7-91.2) 0C = -70.50C

Thespecific heat capacity of water is given as 4.184J/g0C

Theheat gained by water, q, can be gotten from the equation: q = m xspht x Δ0C

Therefore,q = (161.02 x 4.184 x 1.4) =943.190752J

Sincethe heat gained by water is equivalent to the heat lost by metalsample, the specific heat of the metal sample: (-943.190752 = 54.95x spht x -70.5) = 0.243468J/g0C

Trial2

Themass of water &shy= mass of water and calorimeter – mass ofcalorimeter = (159.55-4.18)

=155.37g

Changein temperature of water = final temperature of metal and water –initial temperature of water = (20.1-19.9) 0C = 0.20C

Changein temperature of metal = final temperature of metal and water –temperature of heated metal = (20.1-94.0) 0C = -73.90C

Thespecific heat capacity of water is given as 4.184J/g0C

Theheat gained by water, q, can be gotten from the equation: q = m xspht x Δ0C

Therefore,q = (155.37 x 4.184 x 0.2) =130.013616J

Sincethe heat gained by water is equivalent to the heat lost by metalsample, the specific heat of the metal sample: (-130.013616= 54.95 xspht x -73.9) =0.0320167J/g0C

Theaverage specific heat of the metal = (0.243468 + 0.0320167)/2 = 0.13774235J/g0C

Discussion

Theexperiment tried to determine the specific heat of a metal sampleusing a calorimeter. The amount of heat that the metal lost in thecalorimeter is equivalent to the amount of heat that the watergained. Since the theoretical value of the specific heat of water isknown, the quantity of heat was easily determined. This heat quantitywas then used to calculate the specific heat of the metal and wasfound to be 0.13774235J/g0Cthis value is close to that of leadmetalwith a literature value of 0.128J/g0C.

Theuncertainties in the experiment resulted from the heat that was lostto the surroundings as the metal sample was transferred from the testtube to the calorimeter. This loss of heat could have led to theinconsistent results obtained from the two trials.

Sourcesof error

Themain source of error in the experiment is human error. This errorcould have occurred during the measurement of the weights ortemperatures. Some water could have also spilled as the metal samplewas transferred into the calorimeter resulting to incorrect values.

Recommendation

Whileconducting the experiment, one should be very keen and as accurate aspossible in reading measurements and values. This act will increasethe reliability of the results obtained from the experiment.

WorkCited

Beran,Hein. BasicChemistry Laboratory Manual.

Slowinski,Emil, Wayne Wolsey, and Robert Rossi.&nbspChemicalprinciples in the laboratory.Nelson Education, 2015.