Temperature, being the measure of kinetic energy in molecules of a substance, is a marker for the points at which the phase of matter a substance changes, which makes helpful in finding why substances have their melting/freezing points. Additionally, shape, intermolecular forces, and molar masses all affect the amount of kinetic energy (or the temperature) needed to change a substance’s phase of matter. It is from this the research question is derived: Why do substances have specific melting points and freezing points? With this, it was hypothesized that melting/freezing point of a substance is most affected by either shape, intermolecular force, or molar mass. In order to answer this question and test these hypothesis, the experiment was …show more content…
To start, the procedure only mandated that the freezing temperatures were recorded, which provided better data for the group, but without the melting data there was nothing to which to compare the freezing data in order to easily see where a data point was off, and indicate a bad trial. Additionally, given the limitations of a high school classroom, the systems in which the data was collected added a few uncontrolled variables. When the thermometers went through the stoppers in the top of the test tubes, they did not fit tightly enough to seal the substances from the outside while they heated or cooled. This could have changed the temperatures collected for freezing points by having warmer air coming into the test tube while it was cooling. This problem was magnified by the fact that the thermometers also did not touch equal amounts of the substance, as in the case of palmitic acid barely the tip of it was touching the actual acid such that it was simply hanging in the test tube, while for substances such as water and oleic acid, the thermometer was submerged at least partially in the substance. The temperature inside the test tube could have easily differentiated from the temperature of the substance, especially given the fact that there was some outside air able to get into and out of the test tube (likely affecting the open space most of all). If this lab were to be conducted again, these errors could be mitigated by ensuring there was enough of each substance in the test tubes so that the thermometers could reach them inside the test tube, and perhaps checking various stoppers to find the best fitting hole for the thermometers to limit the outside air that could enter the system. In terms of error in execution of the lab, there were problems with determining when a substance was completely solid, and then taking the temperature. It
The temperature probe was placed into the test tube and recorded the temperature of the freezing solution using Logger Pro software. The test tube was held against the inner glass of the ice bath beaker so the test tube was visible to see when the solution froze over. Once the freezing point was measured, the temperature stopped being monitored and the data was recorded. The steps mentioned above for finding the freezing point, also known as ΔTf, was replicated for the 0.0, 0.4, and 0.6 concentrations. To find the freezing point depression, the equation ΔTf = imKf was used. The molality (m) of each solution was then calculated dividing moles of solute by kilograms of solvent, and the Kf value for magnesium chloride is known to be -1.86. Since magnesium chloride breaks down into three ions in deionized water, it was concluded that the Van’t Hoff factor couldn’t exceed three. For better accuracy, the experiment explained above for finding the freezing point depression and Van’t Hoff factor was re-conducted exactly the same to determine more accurate results. Again, the molality of each solution was calculated, and a graph expressing the change in freezing temperature verses molality
A characteristic property can help identify a substance. A characteristic property will never change even when the volume of a substance is varied. A characteristic property also does not change when a substance changes state in matter. A physical property cannot identify a substance. A physical property will change when the volume of a substance is varied. It can also change when the substance changes state in matter. For example, if the volume and mass of a substance changes then the physical appearance will also change. However, the density, which is a characteristic property, will not change at all. The boiling point of a substance is the temperature that a substance changes from a liquid to a gas. The boiling point of a substance is a characteristic property because the boiling point of a substance will never change even when the volume and mass changes. The only thing that will change is the time that it takes to reach that temperature. If the mass and volume of the substance is small, then it will take a small amount of time for the substance to reach the temperature. However if the mass and volume of the substance is larger, then it will take a longer time to reach the temperature. The purpose of this lab was to see if when the volume of a substance changes so does the boiling point.
Especially with big quantities of a substance, the melting point tends to be a range of values rather than just one value. This is because all the substance will not melt at once; it takes some time to melt at its estimated melting point. However, the hot plate will continue to increase the temperature, even when the substance is at its melting point. Thus, a more accurate range of temperatures will be acquired if the substance is heated slowly. 2.
Matter exists in three basic states: solid, liquid, or gas. A substance experiences a phase change when the physical characteristics of that substance change from one state to another state. Perhaps the most recognizable examples of phase changes are those changes from a solid to a liquid or a liquid to a gas. When a substance goes through a phase change, there is a change in the internal energy of the substance but not the temperature of the substance (Serway, et al. 611).
It was probably either not functioning right or had not been adjusted correctly. If another balance scale was used for the procedure maybe the data could have been more accurate. To continue, another mistake that could have lead to poor data was when pouring the unknown metals into the graduated cylinder to measure the volume, some metals had fell to the ground and only the seen metals was picked up. Some of the metals could have been left on floor after measuring. This loss of metal may have resulted in losing a few grams of the unknown metal. This could have been avoided if the procedures were taken more carefully and slowly whereas no mistakes could've happened. Just like in any experiment, there are errors just like there was in this experiment. The lesson is to learn and improve from the errors on the previous experiments. To improve from the errors, is to use a modern balance scale to recieve a more accurate results. Most objects disfunction as time goes by. Also, the measurements could have been more precise. A more precise measurement could lead to a more accurate calculation. When having a time frame for a procedure, knowing how to manage your time and not rushing through the steps could help the experiment be a success. In every experiment there will be errors that will carry on and remember to not repeat the mistakes
When there is a heat exchange between two objects, the object’s temperature will change. The rate at which this change will occur happens according to Newton’s Law of heating and cooling. This law states the rate of temperature change is directly proportional between the two objects. The data in this lab will exhibit that an object will stay in a state of temperature equilibrium, unless the object comes in contact with another object of a different temperature. Newton’s Law of Heat and Cooling can be understood by using this formula:
In conclusion, this experiment allowed us, the students, to use theories learned in class to real life applications, or real life applications that we will soon encounter. The lab better prepared us for what may be expected in the future, and allowed us to determine different factors that affected our results in more than one possible way. The cold pack experiment lab that was conducted by my group and I, had resulted in us facing errors such as measurement errors, errors including the calorimeter and errors including our unknown salt. These errors were recorded and explained to better help us prevent it from occurring again. By following the correct procedure and having the correct materials required, we were able to determine the final enthalpy. That allowed us to determine what our unknown salt was, which was ammonium chloride.
Introduction: A phase change is a result from the kinetic energy (heat) either decreasing or increasing to change the state of matter (i.e. water, liquid, or gas.) Thus saying, freezing is the phase change from a liquid to a solid which results from less kinetic energy/heat. Also, melting is the phase change from a solid to a liquid which results from adding kinetic energy/heat. So, the freezing and melting point of something is the temperature at which these phase changes occur. Therefore, a phase change will occur when a vial of 10 mL of water is placed into a cup of crushed ice mixed with four spoonfuls with 5 mL of sodium chloride for 30 minutes. If 10 mL of water is placed in an ice bath, it will then freeze at 5 degrees Celsius because the kinetic energy will leave quicker with the ice involved. The purpose of this lab is to observe what temperature the water must be to undergo a phase change.
the water baths I think were accurate enough but having two thermometers in each bath maybe would have helped to hold the temperature readings more accurately. We were not given any instructions either to shake or not to shake the test tubes with the coloured solutions before inserting them in the spectrophotometer to read the absorbance. By shaking each test tube a certain number of times before putting it in the spectrophotometer could have improved the accuracy of the absorbance of the solutions.
The purpose of the lab was to show the effect of temperature on the rate of
The last part of experiment 5, was learning about specific gravity and temperature. Specific gravity does not have any units, it is unitless. When measuring for the temperature, we used a thermometer to calculate the Celsius of the water, 10% sodium chloride, and isopropyl alcohol. The specific gravity uses a hydrometer to measure the gravity of the liquids. Using the hydrometer, to figure out the measurements we have to look at it from top to bottom. The water for specific gravity was .998 while the temperature of it was 24
its state (Solid, liquid, gas); thus water has a higher melting point and a higher boiling
These phases can go from one to another when affected by certain things, which is known as phase changes. To switch from a solid to a liquid, the solid must melt. On the other hand, to switch from a liquid to a solid, freezing must occur. Furthermore, to switch from a liquid to a gas, a process known as evaporation must take place. In contrast, to go from a gas to a liquid, condensation must take place. Furthermore, sublimation must take place for a solid to turn to a gas. Inversely, deposition must occur for a gas to change to a solid.
Solids, liquids, and gases are the three main, or fundamental phases of matter. Each one has a different density and a different level of stability. What determines the stability of each phase is the bond between it's atoms. The tighter the bond between it's atoms the more stable that phase of matter is. Solids are the most stable form of matter, followed by liquids, and then gases.
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.