Introduction/Thesis
Calorimetry is a technique that is used to measure the amount of heat that is involved in a physical or chemical process. This technique is used to measure the total amounts of heat that is transferred from and to a substance when two substances of different temperatures come together. In this case, the heat is exchanged through a calibrated object known as the calorimeter. The change in temperature is converted into the amount of heat. When measuring the heat transfer in this case, there is the system, which is the substance that undergoes the chemical or physical change and the surroundings, which are the components of the measurement apparatus that provide or absorb heat from the system. A calorimeter is used to measure the amount of heat that is involved in the physical or chemical process.
Background
When two samples of liquids at different temperatures are mixed, the mixture that results has a temperature that is between that of the hot and the cold original samples. This temperature balance is an indication of sharing.
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Temperature vs. Heat
In an instance when you hold a piece of metal that is at a lower temperature than that of your body, you will have a sensation of a lower temperature for a moment. At this point, what is happening is a flow of heat from your body into the metal, and at some point, the two temperatures reach a balance. Heat is the energy that flows from an object at a higher temperature into an object that has a lower temperature, and it flows until the two bodies reach a state of thermal equilibrium. Bodies that are at thermal equilibrium have a common temperature. This transfer of energy is facilitated by internal energy, which is the sum of the molecular potential energy, the molecular kinetic energy, and all the other kinds of molecular energy of the bod in question. The average internal energy per molecule is known as the absolute temperature. That said, mixing two liquids of different temperatures together results in the transfer of internal energy through the interaction of the molecules. The energy that is transferred from a warmer body to a cooler body is called heat. Suppose you mixed together approximately 100 g of 24 °C water with 100 g of 12 °C iron. What would you predict for the equilibrium temperature of this mixture? Less than 18 °C 18 °C Greater than 18 °C In this case, T f = _18__ °C
The amount of temperature change is determined by the mass, the type of material, and the quantity of heat flowing.
Where, m is the mass in kg, c is the specific heat capacity in Joules/kg∙C°, and ΔT is the change in temperature in C°. An increase in temperature will increase so ΔT and Q will be positive and the vice versa. When a quantity of heat Q, flows from one part of a system to another, the total internal energy of the system is unchanged. Q represents the amount of energy simultaneously lost by one part of the system and gained by another.
Determining the specific heat capacity of an unknown material.
In addition to water, ice, and iron, the Dispens-O-matic can dispense a quantity of an unknown solid.
When you’ve determined c M , use the tables in your textbook to determine what material you judge the mystery material to be. Indicate how accurate your result is by calculating the percentage error . Specific Heat of Water = 4.18 J/g*C
Final Temperature of water was 28.70 0 C
Specific Heat of Metal X?
Final Temperature of Metal X = 28.70 0 C
Calculating the specific heat for the unknown metal.
The amount of heat transferred to the water is
Therefore, the specific heat capacity of the metal X is
The closest matching metal for this specific heat is Titanium.
Phase Changes and Latent Heat
The materials listed in Table 3 are mixed together in a calorimeter. The irregular nature of the ice cubes are irregular means that one may you may not get exactly 400 grams of ice. The calorimeter are watched as they approach equilibrium temperature.
Determining the final temperature of a mixture of ice and water.
400 g of water hotter than 70°C is combined with 200 g of ice in a calorimeter. A
data table
is provided below to hold your data. Starting from
, write the full equation with all the individual terms. The theoretical value for T f is determined and it is compared with the experimental values. The percentage error is then calculated
Methodology
Purpose
To investigate the flow of heat between two bodies due to a difference in their temperatures.
To investigate the flow of heat involved in changes in phase.
Equipment Virtual Calorimetry Lab PENCIL
Approximately 100 g of 24 °C water was mixed with 100 g of 12 °C water. The equilibrium temperature of this mixture is estimated to be
The same is tried using a calorimeter and it confirms a temperature of
Data
| Table One: Mixing Hot Water with Cold Water, and then Col Iron | |||||
| Trial | Mass (kg) | Initial Temperature ( 0 C) | Final Temperature ( 0 C) | Change in Temperature ( 0 C) | |
| 1 | Hot Water | .100 | 24 | 18 | -6 |
| Cold Water | .100 | 12 | 18 | +6 | |
| 3 | Hot Water | .100 | 24 | 18 | -6 |
| Cold Iron | .100 | 12 | 22.8 | +10.8 | |
|
Table 2: Mixing Hot Water with Cold Iron Specific Heat of water, c w =4186J/Kg.C 0 Specific Heat of Iron, c I =452J/Kg.C 0 |
|||
| Mass (kg) | Initial Temperature ( o C) | Final Temperature ( o C) | |
| Water | .200 | 10 | 28.70 |
| Iron | .800 | 80 | |
|
Table 3: Mixing Warm Water with Cold Iron Specific Heat of water, c w =4186J/Kg.C 0 Specific Heat of Ice, c I =2000J/Kg.C 0 |
|||
| Mass (kg) | Initial Temperature ( o C) | Final Temperature ( o C) | |
| Water | .400 | 90 | 39.2 |
| Ice | .400 | -5 | |
|
Table 4: Mixing Warm Water with Cold Ice Specific Heat of water, c w =4186J/Kg.C 0 Specific Heat of Ice, c I =2000J/Kg.C 0 Heat of Fusion of Ice, L FI =3.35*10 5 J/Kg.C 0 |
||||||||
| Mass (kg) | T WO ( o C) | T f =T Wf ( o C) | N/A | N/A | ||||
| Water | .400 | 70 | 31.2 | N/A | N/A | |||
| Ice | .200 | -250 | 31.2 | |||||
Analysis
As seen in table one, the hot water in trial 3 cooled by only a small amount relative to the amount of cooling in trial 1. And the temperature of the cool metal changed by a much larger amount than the equal mass of cool water. This is an indication that a much smaller amount of heat is required to produce a given change the temperature of a given mass of iron.
Table 3:
for each material is calculated.
Table 4 Analysis
Conclusions
In these experiments, the warm and hot water lost a lot of energy. But the ice seems to have gained only about 7% of it. The ice slowly disappeared. When the ice melts its molecules undergo a large increase in potential energy as they change from a rigid crystalline form to a liquid form. The warm water molecules are the source of this energy. This change in potential energy is known as a phase change – the solid ice changed to liquid water. This significant amount of extra energy is accounted for by adding an extra term, miLf, where Lf, is the latent heat of fusion. The heat of fusion for ice is 33.5×104 J/kg.
