Â“In reactions between various metals and the same other single
reactant, the more reactive the reacting metal the stronger will be
the bonds in the metal product formed . This will be observable
through more exothermic enthalpy changes of reaction for more reactive
The hypothesis is the prediction which should help me to answer the
research question. If the hypothesis is proved correct through
experimentation then I can apply it to predict the place of the metals
I have investigated in the reactivity series. This will be as simple
as arranging the metals investigated in order of decreasing enthalpy
change of reaction and then comparing this list with published and
accepted data. If they match then the hypothesis will be proved
correct. If this is true then the answer to the research question will
be yes as I will then be able to use enthalpy change of reaction to
work out the place of a metal in the reactivity series without the
need to refer to a book.
The hypothesis is based on the following explanation. The enthalpy
change of a reaction is the heat evolved when a reaction takes place.
All chemical bonds hold heat energy within them. Enthalpy change of
reaction is the difference between the heat held in the bonds of
In this essay, the author
Explains the use of enthalpy changes of metal reactions to experimentally test the reactivity series of common metals.
Argues that enthalpy changes of reaction can predict the place of a metal in the metals reactivity series.
Explains that if the hypothesis is proved correct through experimentation then they can apply it to predict the place of metals they have investigated in the reactivity series.
Explains that arranging the metals investigated in order of decreasing enthalpy change of reaction and comparing this list with published and accepted data will prove the hypothesis is correct.
Explains that the enthalpy change of a reaction is the heat evolved when the reaction takes place. all chemical bonds hold heat energy within them.
Explains that an exothermic reaction would be considered to have a negative enthalpy change because heat energy has been given up into the surroundings.
Explains their hypothesis based on the understanding that more reactive metals will create more stable compounds on reaction, meaning less energy will be held in their strong and stable bonds.
Explains that the reaction between lithium metal and copper sulphate is simple and safe, and should be spontaneous with a good number of common metals.
Explains how they calculate the enthalpy change of the reaction using î” h = m c ( tinitial – tfinal).
Explains that the independent variable is the choice of metal in the experiment, which changes from experiment to experiment. the dependant variable changes because of the changing metal.
Explains that uncontrolled variables are aspects over which they have no effective control, such as the ambient temperature in the cup which may change with external temperatures. the surface area of the metal affects the rate of reaction.
Explains that the faster the reaction, the harder it will be to measure the enthalpy change. metal filings can mitigate this by using the thermometer.
Explains that the reaction will be conducted in the insulated styrofoam cup to minimise the heat loss to the surroundings.
Explains how the temperature of the reaction is measured in situ by measuring 25cm3 of copper sulphate into a cup and adding 0.5 g (an excess) of metal to the stopwatch.
Explains that leaving the cup is responsible for the fall in temperature after this point. it is important to take further readings after the peak temperature has passed.
Explains that heat loss error will mean that the temperature measured will not take account of all the heat generated by the reaction.
Explains that they have chosen five metals with which to conduct the reaction. they expect them to react with copper ions on the basis of their standard electrode potentials and cover a reasonable range of the reactivity series.
This lab has to do with enthalpy and calorimetry. Enthalpy is a measure of the amount of energy in a system, which is the part of the universe we are studying. Equation one is used to find enthalpy.
(Equation 1) ΔH=E +PV
In this essay, the author
Explains that equation one is used to find enthalpy and calorimetry, which measures the amount of energy in a system.
Explains that h is the change in heat, e is energy, p represents pressure, and v is volume. equation two is for the enthalpy of a reaction.
Explains that calorimetry is used to measure enthalpy. it measures how much heat is flowing.
Explains that the initial and final temperatures were found for each trial (table 1). these results were averaged, and equation three was used to determine the grams used.
Explains how the grams of each salt used in the experiment were divided by the change in temperature recorded. equation 4 was used to determine the price.
Explains that $0.75, $0.36, and $0.19 were used because they cover the cost of the plastic bag, labor and overhead costs.
Explains the lab's goal to determine which two salts would be best to make a profitable hot and cold pack.
Explains that styrofoam cup calorimeters will be used for this lab. each packet must be stored at room temperature, cost less than five dollars, and contain a salt and water.
Explains that the lab lab requires room temperature water, spoons, digital scale, graduated cylinder, plastic boats, styrofoam cups, and a lab quest temperature probe.
Investigate the difference in enthalpy of combustion for a number of alcohols
I am going to investigate the difference in enthalpy of combustion for a number of alcohols, the enthalpy of combustion being the 'enthalpy change when one mole of any substance is completely burnt in oxygen under the stated conditions'. I will be attempting to find how the number of carbon atoms the alcohol contains effects the enthalpy change that occurs during the combustion of the alcohol.
I plan to measure the enthalpy change by burning the alcohol, using a spirit burner, I will then use the heat produced during the combustion of the alcohol to heat 100ml of water that will be situated in a copper calorimeter directly above the burning alcohol. The calorimeter is made of copper as copper has a high thermal conduction value, this basically means that it is a good conductor of heat so a lot of the heat the copper receives will be passed on to the water which I am then able to measure.
In this essay, the author
Explains that they will investigate the difference in enthalpy of combustion for a number of alcohols.
Explains that they plan to measure the enthalpy change by burning alcohol, using a spirit burner, and then use the heat produced during the combustion of the alcohol to heat 100ml of water.
Explains that during the experiment, they will take a number of measurements, such as the initial temperature of the water and initial mass of alcohol. they will then burn the alcohol until an increase in temperature has occurred.
Explains that they will need to repeat their experiment a number of times and take an average so they are sure of an accurate result.
Explains that the calorimeter is held directly above the spirit burner by a retort stand and clamp, and the mercury thermometer, which is very accurate, will be used to measure the water temperature.
Predicts that alcohols with a greater number of carbon atoms within the molecule will have higher enthalpy of combustion than those with less. bond breaking requires energy while bond making releases energy.
Explains the balanced equation for the combustion of methanol. the type and number of bonds within each mole of reactants and products are shown.
Explains that the total energy required to break the bonds in the reactants is 2807.5 dh/kj mol-1, and the difference between them and products is 524.5
Explains that the energy released by the alcohol is only an approximation for the combustion of methanol because the bond enthalpies vary slightly from one molecule to another.
Describes the alcohols that they plan to use in their investigation, including methanol, ethanol and propanol.
Explains that methanol ch3ho + 1.5o2 (g) co2 + 2h2o (l)3 c__h 413 1,5o=o 497
Explains that the bond enthalpies worked out above clearly show an increase in the overall energy that is released as the alcohols increased in size.
Compares the enthalpy of combustion (dhc) of different alcohols.
Explains that they are going to use propan-1-ol and butan-l as representatives of the two alcohols. they are large enough molecules to form isomers and have the closest structural arrangement.
Explains that they need to use alcohols with as similar structure as possible, with the only difference being the number of carbon atoms within the molecule.
Explains that alcohols are flammable, so they need to be handled with care, avoiding spillages, and kept in a suitable container.
Explains that their experiment is safe as long as it is carried out sensibly taking heed of the general laboratory rules.
Explains that alcohol initial temperature +/- (oc) finaltemperature (g) methanol 21 43 22 213.18 212.06 1.1221
Explains that the bottom of the calorimeter had a black sooty type substance on it, which was affecting their results for butan-1-ol.
Explains that the smaller alcohol's needed less energy to break the bonds in the reactants and so more energy is needed to initiate the reaction.
Explains that carbon is a better insulator than copper, as it has lower thermal conductivity value and stops heat getting through to heat the water as there should be.
Explains that their results show a clear increase in the energy released per unit mass of alcohol. they need to find which alcohol releases the most energy per mole.
Explains that energy mass x temp increase depends on the substance you are heating, it is called the specific heat capacity.
Explains that the mass of water heated, 100g, is the heat energy exchanged during the experiment, which needs to be converted to heat taken in per mole of alcohol burned.
Explains that the heat absorbed by the calorimeter can be worked out.
Explains that the two values worked out above for the energy absorbed by the water and the calorimeter give the total.
Explains the average enthalpy of combustion for the alcohols in the table.
Compares their results to the bond enthalpy values that they had worked out earlier.
Explains that it is possible to measure the exact enthalpy of combustion using a bomb calorimeter apparatus. heat losses can be eliminated if the thermo chemical investigation is coupled with an electrical calibration.
Compares the values of the enthalpy of combustion given by the bomb calorimeter to their results.
Explains that methanol was the least accurate at 38.9% of what it should have been and propon-1-ol at 49.5%.
Opines that their results have been consistently accurate, with the gap between the most accurate and the least accurate being only 10%. this gives them the impression that they are not just wrong because of human error.
Explains that the enthalpy's of combustion that they are comparing their results to were measured under different conditions so this means they would be different any way.
Explains that heat produced in the experiment was aloud to escape before it had even entered the apparatus and even heat that got into the water could escape back out of the calorimeter.
Explains that they redid the experiments now using the insulation material, attaching it to the sides of the calorimeter. the results were an improvement on the previous attempt.
Explains that their results show a clear increase of around 9% although this does vary from alcohol to alcohol. the heat produced does not even enter the apparatus, it is aloud to escape immediately.
Opines that the accuracy of their experiment could have been improved by using a bomb calorimeter, which was not available to them.
Compares the enthalpy of combustion from the bomb calorimeter to the results that they got from their experiments. the only thing that could have been improved was to measure all the heat energy that had been released by the combustion of the alcohols.
Opines that lining the reflector with silver/ shiny surface would keep more of the heat produced during combustion close to the calorimeter so more is absorbed.
Opines that there are other aspects of the enthalpy of combustion of alcohols that they could have investigated.
The higher the temperature change is, the higher the enthalpy change will be and vice versa.
In this essay, the author
Explains the aim of this investigation was to determine how five different metals of different reactivity reacting with copper sulfate solution would affect the enthalpy change of the reaction.
Hypothesizes that as the reactivity of different metals increases, the absolute value of enthalpy change is expected to increase as well.
Explains that the idea for this investigation was developed from an in-class experiment done during our energetics unit where we learned about enthalpy changes within a reaction by conducting an experiment between copper sulfate solution and zinc.
Describes the enthalpy change in a single displacement exothermic reaction, which is calculated by finding the temperature change within the reaction.
Total energy difference is 1840 kJ/mol – 1371.5 kJ/mol = 469 kJ/mol, which indicates that the reaction is endothermic and that 469 kJ of heat is needed to be supplied to carry out this reaction.
In this essay, the author
Explains that bond energy is a measure of the amount of energy needed to break apart one mole of covalently bonded gases.
Explains that when more bond energies of the bond in different molecules that are taken into consideration, the average will be more accurate.
Explains which bond in this list has the highest bond energy? the lowest bond?
Explains that atoms bond together to form compounds because they attain lower energies than they possess individually. when a chemical reaction occurs, molecular bonds are broken and other bonds form different molecules.
Explains that bond energy is used to describe the structure and characteristics of a molecule.
Explains that although each molecule has its own characteristic bond energy, some generalizations are possible.
Explains that triple bonds are higher energy bonds than double and single bonds, but not necessarily 3-fold higher.
Explains that when a chemical reaction occurs, the atoms in the reactants rearrange their chemical bonds to make products.
Explains that textbooks and instructors consider heat as an independent "species" in a reaction. this is rigorously incorrect because one cannot "add or remove heat" as with species.
Explains that the breakage and formation of bonds is similar to a relationship. atoms are happier when they are "married" and release energy.
Explains that if the bond energy for h-cl is 431 kj/mol, what is the overall bond energies of 2 moles of hcl?
Explains that bond energy is the energy required to break a bond between two atoms. the enthalpy change deals with breaking two moles of o-h bonds.
Explains that the reaction is endothermic and requires energy to create bonds. the h-f bond has the highest bond energy since the difference in electronegativity is the greatest.
Explains that general chemistry: principles and modern applications. 9th ed. upper saddle river: pearson education, inc.
... model for the thermodynamics and fluid mechanics calculations for this system need to be presented.
In this essay, the author
Explains that foaming systems are widely used in different applications especially in the cooling applications due to the following benefits.
Explains that fogging systems require clean water handling components of evaporative cooling systems. maintenance actions will be needed based on the system type.
Defines sprinkler system as any kind of water emitting instruments whose main function is to drip or spray water on pigs to rise evaporative cooling.
Explains the different types of evaporative cooling pads, which have water running over and down the surfaces to cool the incoming air to a building.
Defines a fogger system as any kind of high-pressure nozzle up to 200 psi or low- pressure hose that sprays water into the surrounding air as fine fog or mist.
Explains that sprinklers have the smallest maintenance requirements compared to other components.
Describes the steps to be taken to check the filters, periodically, and illuminate the sediments.
Recommends checking the flow from nozzles daily or weekly to ensure that water flows from each one.
Recommends checking the functioning pressure of sprinklers weekly or monthly to ensure that they are working at the desired pressure.
Explains that the pad systems can be freely moistened based on the system installation and operational parameters. the maintenance procedure of the bad system is presented in the following steps.
Recommends allowing pad system to dry at least four hours each night to minimize algae development and maintain the life of the pad.
Explains that once daily drying is not enough to control the growth of algae, a chemical can be added for controlling algae.
Explains how to minimize mineral deposits on pads by making sure that water is distributed uniformly along the pad length.
Explains that fogging systems require a continuous maintenance, it sometimes requires daily maintenance based on the water quality and the system type.
Describes the steps involved in the periodic check for the filter and eliminates sediment buildup.
Explains step 2 involves a weekly check for the operating pressure to make sure that nozzles are operating at the wanted pressure.
Explains that the project aimed to demonstrate the fogging sprinkler system, what is it, how it works and distributes, and a mathematical model for the thermodynamics and fluid mechanics calculations.
Explains that in order to achieve the main aims of this project, the following objectives will be followed.
Describes the literature review that describes the previous efforts done by others in the main topic and provides the latest improvement of the designs of this system.
Explains the project plan and the time required to complete each step.
Explains the three main types of evaporative cooling systems: sprinkler systems, pad systems and fogger systems. the basic fogging system comprises an atomizing nozzle, motor, high pressure pump, and plumbing.
Explains the effect of water quality on fogging and sprinkler systems.
Explains that the fogging systems for cooling air purposes will be discussed in the first chapter. theoretical analysis and thermodynamic and fluid calculations will also be presented.
Hess’s Law is also an important concept in this lab. It states that the enthalpy of a reaction is independent of the steps it takes to go from reactant to a product. It happens because enthalpy is a state function. A state function depends on the initial and final state but not the actual process. The Hess’s Law is used to calculate the heat formation of Magnesium Oxide. The amount of heat necessary to create one more mole of a substance is called the Enthalpy of Formation.
In this essay, the author
Explains that the lab's purpose is to understand how to calculate the calorimeter constant by using the instrument. calorimetry is a word that comes from both latin and greek.
Explains that styrofoam cups act as calorimeters due to their insulating properties. since most of the heat that forms is absorbed by the solvent, the temperature can be altered.
Explains that when the amount of hot water released and cold water absorbed does not coincide, it means the calorimeter is absorbing some of the heat.
Explains the hess's law, which states that the enthalpy of a reaction is independent of the steps it takes to go from reactant to product.
where Hp(t) is the partial heat of cure reaction at time t, ΔHTotal is the total heat of cure reaction. The rate of conversion (dα/dt) at a given temperature (T) is generally denoted by Eq. (2):
In this essay, the author
Explains that lap shear test was conducted using two 102 251.6 mm dimension acid etched aluminum substrates with a 12.7mm overlap area. shear tests were carried out as per astm d-1002.
Explains the fractograpy of the adhesive joints of specimens after lap joint test was studied using scanning electron microscopy (evo ma 15, carl zeiss smt, germany).
Explains that x-ray diffraction analysis of cloisite 30b and epoxy nanocomposite adhesives reinforced with c30b was carried out to examine their degree of intercalation/exfoliation.
Explains that differential scanning calorimetry (dsc) was used to examine the curing behavior of pristine epoxy adhesive and nanomaterials based adhesives.
Explains that to analyze the curing kinetics of dgeba/teta system with or without various nanomaterials, the study of activation energy (ea) is contributory.
Explains that the rate of conversion (d/dt) at a given temperature (t) is generally denoted by eq.
Explains that the reaction rate constant k(t) follows arrhenius form and can be indicated by eq (3).
Explains that the activation energy (ea) can be calculated using different models.
Explains that by plotting the linear relationship of ln(/(t_m2 )) vs
Explains that thermal stability and degradation kinetics studies of adhesives were examined using thermogravimetric analysis (tga). samples of about 10mg were taken and scanned at heating rates of 5, 10, 15
Explains that the e can be calculated from the slope of the plot ln(/(t_md2 )) vs
Describes the ultrasonic technique used to disperse nanomaterials in the base resin. transmission electron microscopy (tem) with 120 kev accelerating voltage at different resolutions was used.
Explains that degradation kinetics studies allow us to examine in which temperature range the systems were decomposed with reference to the virgin material.