1. Preliminary Investigations of Energy Balances ENCH 4350 9/7/2010 Hemali Dholakia Jessica Lacy

2. Procedure Data Heating with Coffee Pot Heating with Microwave Ovens Heating with Hot Plate ∆H and Student’s T Test Results Challenges Objectives

3. Procedure: ◦ Observe energy and material balances ◦ Determine average change in enthalpy (∆H) using calculations and experimental data ◦ Determine the measure of uncertainty of experimental data using the Student’s T Test

4. 97.8 o C -1.0 o C Thermometer Calibration

5. Material and Energy Balance H = C p *m*∆T, where C p H 2 O= 1 cal/ o C*g Hot Water: H= 100 g x 63 o C = 6300 J Cold Water: H = 100.4 g x 1.9 o C = 190.76 J Determine ∆T: ∆T = H/total mass ∆T = 32.4 o C

6. Hot and Cold Water Mixed

7. Heating with Coffee Pot

8. Heating with Microwave Ovens (EMCS 441)

9. Heating with Microwave Ovens (EMCS 427)

10. Heating with Hot plate

13. Microwave (427) Time (30 second intervals) Watts

14. Time (30 second intervals)

15. Energy Comparison Using Experimental Data

16. Energy Comparison Using Calculated Data

18. Uncertainty of Experimental Data Determined by Student’s T Test Heating ApparatusUncertainty of ∆Q (95% Confidence, n=2, t=6.3) Coffee Pot14916 J ± 0 Microwave Oven (427)61296 J ± 3.1 Microwave Oven (441)58657 J ± 3.1 Hot Plate26631 J ±3.1

19. Results Calculated and experimental data did not match ◦ Experimental data factored in time (H = watts*time) ◦ Calculated data determined energy usage per ΔTemp (H = C p *m*∆T) Large time interval to reach >90 o C causing large electrical energy consumption All three appliances consumed more energy (J) than expected by H equation

20. Challenges Time interval used based on how long temperature reached >90 o C for microwave and hot plate ◦ Coffee Pot data dependent on time for water to cycle through system