From my research I found out that there are two laws of Thermodynamics:
The first law states that the net heat transfer ( Q) of a systems equal to the sum of the thermal energy.
The second law states that the entropy of an isolated system never decreases. This means that heat cannot be 100% converted to useful energy because the heat released to entropy is never returned to the system.
Entropy is like internal energy; it is a thermodynamic quantity that belongs to any system of objects. It is proportional to temperature. As the temperature increase, entropy increased. In a microscopic level, entropy measures the amount of disorder in a substance. When heat is added to the substance, the particles that make up the substance move faster in a random way. The greater the velocity of the particles this implies more disorder for the substance; therefore increasing its entropy.
To work out how much energy is used Power and Time are required:
This is the equation t work out Power:
Power = Current * voltage.
Thus to work out energy we use this equation:
Energy = current * voltage * time
The substance that I will be trying to determine its Specific Heat Capacity is Ethanol.
Ethanol, C2H5OH is the second member of the aliphatic alcohol series. Most of the ethanol used is a mixture of 5% water because pure ethanol known as absolute ethanol is too expensive. Ethanol is prepared by a 95% solution, which results from the fermentation of sugars.
Ethanol used in industry is made by reaction of ethane and steam.
C2H4 + H2O= C2H5OH
Ethanol’s has a boiling point of 78.3 degrees centigrade, which is lower than water’s boiling point.
PREDICTION
I predict that the specific heat capacity of ethanol will be less than that of water, but greater than that of any solid. I’ve come up with this prediction because ethanol has a boiling point which is significantly lower than that of water but it’s still a liquid so it’s specific heat capacity should be between 2000-3000.
I suggest this because it’s a liquid and from my research require much more energy to warm up, compared to solids but because it’s more dense than water and it’s particles are closer together than those of water, it would mean that it would require less heat compared to water.
I predict that the results would produce a graph that would show the increase of energy as temperature increases. I predict that line produced by the results should be a straight line and should go through the origin but from my preliminary work I found this wouldn’t happen in the real world because there would be heat loss. Working out the gradient of the graph would produce the specific heat capacity of ethanol. From my preliminary work I learnt that some heat was used up to heat up equipment some was lost through radiation by the beaker, convection we taking place which meant temperature rise was less than should be.
METHOD
Equipment
RV power pack
Joule meter
Weighting scale
Stop clock
Connecting wires
Heatproof mat
Immersion heat
Beaker and Lid
Wool
Thermometer
Ethanol (0.3kg)
The equipment will be set-up as shown in the diagram. As temperature will be variable, that will be controlled so the temperature should rise by at least 10 degrees to be able to plot a graph. I will do three observations to be able to work out an average to plot the graph.
From the my preliminary work I learnt that I should use a smaller beaker, less liquid, smaller heater and the beaker should be wrapped by material to reduce heat loss. The thermometer and joule meter reading should be recorded after every 2 minutes.
SAFETY
As the experiment involves electricity and liquid, safety precautions will apply. The beaker should be placed on a heat proof mat, don’t touch the power pack or connecting wires with wet hands as this can give electric shock. The heater will be hot so one should be aware, it should be placed on the heatproof mat when removed from the beaker and, Spillages of liquid should be avoid as this makes the floor slippery.
FAIR TEST
To be able to obtain accurate results other variable (mass) should be kept be kept the same through out all experiments. In all 3 experiments the same beaker should be used, same heater, thermometer, joule meter and power pack. All three experiments should be done in the same part of the room to avoid temperature variation.
BIBLLIOGRAPHY
MODIFICATION
In my method I had originally planned to take thermometer reading after every 2 minutes but when testing the equipment and took the readings I found out the temperature rose rapidly and was unable to obtain sufficient readings that would produce a graph, so decided to take readings after every 1 minute. To prevent heat loss I had planned to use a layer of wool to wrap around the beaker but decided to add more layers of aluminium bubble wrap to keep heat loss as minimal as possible.
THE RESULTS
Implementing:
When I finished testing the equipments the heater was still hot which would have meant the next experiment would have had unfair testing conditions. To resolve the problem I dipped the heater in cold water for 7 minutes to cool it off and placed on the table for further 3 minutes gain room temperature.
During the first experiment, the thermometer that I was using had a scale reading from -5 to 100, which made it very difficult to obtain accurate reading. To minimise error with readings I used the same size thermometer but with a smaller scale reading from -5 to 50, that was much easier to see the temperature.
The final condition to change from original plan was that I used a glass lid apart from using a rubber lid to cover the beaker. This was because when rubber lid is used the thermometer could not be viewed without being lifted up but with glass lid, eliminated the need to move around the thermometer to see the temperature.
CONCLUSION
Resulting from the three experiments, I was able to work out average for the energy used and temperature, which I used to work out the temperature rise. To be able to analyse the results properly and accurately I decided to plot a graph using the average temperature rise against energy used.
When I plotted the graph, the out come of the results was a straight line when I drew a linear line of best fit. The out come of my graph agrees with my prediction, which stated that the results should produce a straight line on the graph and it would not go through the origin in the real world.
To be able to work our the specific heat capacity I had to draw a gradient on the graph and use the value from it:
c = Energy _ _
Mass * Temperature Change
Using the gradient, we get:
G = Y Y = Energy
X X = Temperature Change
G = 16000 - 4000 = 12000
20 - 3 = 17
G = 12000
17
To be able to work out the specific heat capacity the mass must be included which was 0.3 kg.
c = 12000
0.3 * 17
c = 2353Jkg-K-
The value that I worked out for the specific heat capacity of ethanol is 2353Jkg- K-. This value agrees with my prediction that the value will be between 2000 and 3000 and to be much lower than the specific heat capacity of water. The specific heat capacity that was produced by the gradient, 2353Jkg- K- is only 57 away from the actual specific heat capacity of ethanol, which is 2410Jkg- K- . If both values were to be rounded to two significant figures the values would be exactly the same (2400Jkg- K- ) which shows how close how close the value i worked out is to the real value.
The Fact that ethanol is a liquid but has a significantly lower specific heat capacity compared to water this can be explained by the fact that ethanol’s is more dense than water and it’s particles are much closer together than those of water which makes it easier for heat to be conducted easily by particles in ethanol. This also explains why the boiling point of ethanol, (78.3 c) is lower than that of water which is 100 c and this also supports my understanding and prediction that ethanol requires less heat than water.
EVALUATION
The experiment procedure that I chose for my investigation is reliable able minimised the margins of errors. This is supported by the fact that all my results were all on of very close to the line of best fit on the graph. The fact that when I used error-bars they were all being touched by the line and the R^2 value is 0.9982 and no anomalous results strongly suggest that the procedure was reliable.
The fact that there are no anomalous results and the R&2 value is very close to 1 means that the measuring equipments and technique were very accurate and this is supported by the fact that the all observation all produced readings which are very similar to each other which helped to obtain good averages. The fact that I used a joule meter a part from using voltmeter and ammeter then working out the energy myself eliminated any calculation errors.
Even though the measuring techniques and equipments helped produce reliable results, there are still errors in the experiment because the line didn’t go through the origin and the value that I worked out for the specific heat capacity is a bit less compared to the actual value. The procedure I used produced errors, which affected the whole experiment. The errors that caused by the procedure are that the all the electrical heating was not all used to heat ethanol because some heat had escaped through convection, as the air in the room was cooler. Some energy was used to heat up the heat, heat up the beaker and thermometer. The fact that the lid did not cover the whole top because of the gaps for the heater and thermometer was being converted to the cooler air in the room.
The limitation from the experiment that stopped me from obtaining a value that is 100% accurate was the heat loss through convection and these can be improved by using a lid that covers the entire top and the gaps for thermometer and heater don’t have any space for air to enter or escape. The fact that some heat energy goes towards heating up the equipments, the equipments should be kept in a temperature that when any electrical energy is given it will all be used to heat up the ethanol and beaker to be wrapped with good insulators so any heat conducted to the beaker will not escape. Doing all these will decrease the amount of heat that is being used in other way than heating the substance.
The main sources or errors would be the taking and recording of the readings. I had to observe and record both readings every minute, which meant that some records were few seconds late or early. This explains the reason the experiments producing minor differences when repeated. The way to overcome this problem is to have three people taking single reading and these would increase the accuracy of the results.
