Energy Transformations and Efficiency: Electrical Energy to Heat Energy

Energy Efficiency Lab 11/15

Integrated Science 3Name:Per:

Introduction

According to the Laws of Thermodynamics, energy can neither be created nor destroyed, but it can be transformed from one form to another. Energy transformations however, are not 100% efficient and some portion of the energy is transformed into a less useful form. Useful energy (energy that can move matter) can be conserved if energy transformations occur as efficiently as possible.

There are many different forms of energy (including heat, light, mechanical, chemical, electrical, and nuclear). Because the different forms of energy have different properties, they are measured using different kinds of instruments and different units. However, because all the forms of energy are related, the various energy units are directly related and can be converted back and forth. The primary purpose of this lab is to determine the factor that relates electrical energy to heat energy.

An electric heater is a device that converts electrical energy into heat energy. The electrical energy is equal to the product of the wattage of the heater and the time the heater is operating.

Electrical energy (watt•hr) = Power rating (watts) x time (hr)

The heat absorbed by the water is determined by using the fact that 1 calorie is defined as the amount of heat required to raise the temperature of 1 gram of water 1 Celsius degree.

Knowing the electrical energy used and the heat absorbed, we can determine the relationship between watt•hours and calories. This relationship is called a conversion factor. Conversion factors are used regularly by scientists in their work. You will use them often for making comparisons in this unit.

Purpose

The purpose of this experiment is to determine which experimental model is best at improving the efficiency of a system that transforms electrical to heat energy.

Control

Students will work in groups toconduct a single trial for the control of the experiment. Complete the data analysis based on the dataand calculations collected by the entire class.

Procedures/Calculations

Raw Data – Record data in the appropriate Raw Data Table

Measure 300.0 ml of tap water using a graduated cylinder. Pour the water into a 400 ml beaker. Record both the volume and mass of the water.
Note and record the wattage rating of the immersion heater.
Place the unplugged immersion heater into the beaker. Do not plug in the heater until it is immersed in water. It will burn out in about 2 seconds!
Place a thermometer into the beaker with water and unplugged immersion heater. Record the initial temperature of the water to the nearest 0.5ºC.
At the same time you plug in the immersion heater, note the time or start a stopwatch. Heat the water until it reaches between 80º and 90º C. The exact temperature is not important.
Unplug the heater before removing it from the water and record the stopping time.
Record the final temperature of the water to the nearest 0.5ºC.
Record the time, in seconds, it took to get to that temperature.
As necessary, repeat the above procedures for all levels of the independent variable. Cool the immersion heater and change to a cool beaker for each new trial.

Calculations – Record data in the appropriate Calculations Data Table and Class Data Table

Use the formulas below and information from the Raw Data Table to calculate the % efficiency of each of your trials. Complete the calculations on a separate sheet of paper and record all appropriate values in the Calculations Data Table. Show all your work.

Formulas:

Electrical energy input: (note that 3600 sec. = 1 hr.)

Temperature change of water:

Heat energy absorbed:

Convert electrical energy input to calories:
Assuming 100% efficiency: Electrical energy input (1 watt • hr ) = Heat energy absorbed (860 calories)
Therefore:

Calculate efficiency:

Use the following guidelines to determine the quality of efficiency as either good or poor.

Good / Poor
75% efficiency or greater / Less than 75% efficiency

Control - Raw Data Table

Type of Insulation / Measurements
Volume of water
(ml) / Mass of water
(g) / Initial Temp of water (ºC) / Final Temp of water (ºC) / Time to heat water
(sec) / Wattage rating of heater (W)
Control

Control - Calculations Data Table

Type of Insulation / Calculations
Electrical Energy Input (w•hr) / Temp change of water
(ºC) / Heat energy absorbed
(cal) / Electrical Energy Input (cal) / Efficiency
(%) / Efficiency Quality
(Good/Poor)
Control

Control - Class Data Table – Efficiency (%)

Insulation / Efficiency (%) / Mean / Standard Deviation
1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10
Control

Control - Class Data Table –Efficiency (Quality)

Insulation / Efficiency
(Good: 75% efficiency or greater or Poor: Less than 75% efficiency) / Mode / Frequency Distribution

1

2

3

4

5

6

7

8

9

10 Good

Poor

Control

Model 1

Students will work in groups to research and design a model to increase efficiency in the control system. The class materials provided are: beaker, thermometer, and immersion heater. All other materials must be easily accessible in the common household.

Brainstorm and list factors that could increase the efficiency of the control system.
Researchthe factors listed above. Take notes from your research on a separate sheet of paper and cite your sources.
Use the information you learned from your research to design an experiment to increase the efficiency of the control system. Complete the design outline below. You should complete two trials for your experiment.

Title (Describe the experiment by using the format, “ The Effect of ___ on ___”)
Hypothesis(Make specific predictions about the experimental outcome using the format, “If…,then…”
Independent Variable (What you will be testing)
 continuous  discontinuous
Levels of I.V.
Number of Trials
(# of times each level is tested)
Dependent Variable(What you are measuring)
Quantitative Measurements (include unit):
Qualitative Measurements (include unit):
Constants (List all conditions which are the same for each trial)

Use procedures and calculations described above to collect data for model 1. Record your data in the data tables below.

Model 1; Trial 1 - Raw Data Table

Type of Insulation / Measurements
Volume of water
(ml) / Mass of water
(g) / Initial Temp of water (ºC) / Final Temp of water (ºC) / Time to heat water
(sec) / Wattage rating of heater (W)

Model 1; Trial 1 - Calculations Data Table

Model 1; Trial 2 - Raw Data Table

Type of Insulation / Measurements
Volume of water
(ml) / Mass of water
(g) / Initial Temp of water (ºC) / Final Temp of water (ºC) / Time to heat water
(sec) / Wattage rating of heater (W)

Model 1; Trial 2 - Calculations Data Table

Model 2

Students will work in groups to research and revise their experimental model.

Reflect on the success of model 1 by answering the questions below.

Briefly summarize the results of your model 1 experiment. What worked? What didn’t work? Include data in your response.
Research methods to improve the efficiency of your model. Cite your source.

Use the information you learned from your research to modify model 1. Complete the design outline below. You should complete two trials for your experiment.

Title (Describe the experiment by using the format, “ The Effect of ___ on ___”)
Hypothesis(Make specific predictions about the experimental outcome using the format, “If…,then…”
Independent Variable (What you will be testing)
 continuous  discontinuous
Levels of I.V.
Number of Trials
(# of times each level is tested)
Dependent Variable(What you are measuring)
Quantitative Measurements (include unit):
Qualitative Measurements (include unit):
Constants (List all conditions which are the same for each trial)

Use procedures and calculations described above to collect data for model 2. Record your data in the data tables below.

Model 2; Trial 1 - Raw Data Table

Type of Insulation / Measurements
Volume of water
(ml) / Mass of water
(g) / Initial Temp of water (ºC) / Final Temp of water (ºC) / Time to heat water
(sec) / Wattage rating of heater (W)

Model 2; Trial 1 - Calculations Data Table

Model 2; Trial 2 - Raw Data Table

Type of Insulation / Measurements
Volume of water
(ml) / Mass of water
(g) / Initial Temp of water (ºC) / Final Temp of water (ºC) / Time to heat water
(sec) / Wattage rating of heater (W)

Model 2; Trial 2 - Calculations Data Table

Data Analysis, Graphing and Discussion

Use your data to calculate statistical calculations for central tendency and variation for all levels of the independent variable. Record the results in the Summary Data Tables.
Construct appropriate graphs to best represent the results of your experiment.
Use the Lab Report Format to write a discussion for this experiment.

Summary Data Table – Quantitative Data

Type of Insulation /

Efficiency (%)

Mean

Standard Deviation

Control
Model 1
Model 2

Summary Data Table – Qualitative Data

Type of Insulation

Quality of Efficiency (good/poor)

Mode

Frequency Distribution

Control
Model 1
Model 2

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