The products of the combustion of hydrocarbons are carbon dioxide and water. Many hydrocarbons are used as fuel because their combustion releases very large amounts of heat energy. Ethanol can be used as a fuel source in an alcohol lamp. Write the balanced equation for the combustion of ethanol. Ethanol and oxygen are the reactants. Remove heat, oxygen or fuel and the fire goes out. In suppression of a wildfire, the objective is to stop combustion by removing or altering one or more sides of the triangle.
Stages of combustion: flaming stages see pictures from lab. Transition — fuel is partially consumed by combustion while flaming continues in portions of the fuel resulting in initiation of smoldering and smoke generation.
Smoldering — combustion of the fuel is essentially complete where oxygen is available and smoldering continues resulting in smoke generation.
Suppressing fire and smoke generation segment on Suppression. When a wildfire has started, we try to remove the oxygen side of the triangle by smothering the fire with a fire retardant, foam, dirt or water in a fine spray or fog. They will replace the oxygen around the fuel affecting one side of the fire triangle. They also absorb heat and thus also alter the heat side of the triangle.
Retardants will coat the fuel and protect it from the heat even after the water has evaporated. They also inhibit the flaming combustion by chemical action. Foams also coat the fuel and last longer than water. They reduce heat as well as supply of oxygen to the fuel. They will adhere to vertical fuel and can be easily applied by ground units. Water absorbs vast amounts of heat, especially when applied as a fog.
Each droplet absorbs a large amount of heat which turns the water into a hot gas or vapor steam. The hot steam is then dispersed by the wind into the atmosphere.
Finally, the results of this investigation have implications for inquiry into student understanding. The application of the specific combustion rules reported here is only problematic in the context of non-hydrocarbon combustion; in all situations in which hydrocarbons are burned in the presence of oxygen, carbon dioxide and water vapor are produced. Thus, students' misunderstandings may be masked by exam or other research questions such as the burning candle question posed in the context of hydrocarbon combustion.
Instructors and researchers may need to ask questions in multiple contexts in order to understand student thinking. You cannot burn Iron filings and get copper oxide. It is not possible to generate, in the case of reaction b , CO 2 molecules without the presence of carbon atoms in the first place. If one argues that carbon is present in the air and is utilized in the reaction, then it must be included in the reactant side to make the equation valid.
Also, since beryllium powder is burning, it should produce CO 2. Since it did not say that carbon dioxide and water are the ONLY products of the reaction, it is possible that any one of the 4 choices could have been what was burned. Wood is also an applicable answer because it gives off steam and carbon dioxide, it may not be a hydrocarbon though as far as my knowledge goes.
DOI: Received 28th April , Accepted 31st July Abstract On the basis of responses to written questions administered to more than one thousand introductory chemistry students, we claim that students often rotely apply memorized combustion rules instead of reasoning based on explanatory models for what happens at the molecular level during chemical reactions.
All rights reserved. The specific answer choices in this question were based on the most common student responses to the original beryllium oxide question Fig. Table 1 Populations that received each written question. Table 2 Percentages of students who chose each product in response to the beryllium oxide question. Table 3 Percentages of students who selected each chemical equation in response to the symbolic beryllium oxide question.
Table 4 Percentages of students who chose each reactant in response to the unknown chemical question. We can think of several reasons that this may be the case: 1 Students may have missed our request that they select all possible reactants. Table 5 Percentages of students who indicated changes in amounts of oxygen, carbon dioxide, and water vapor in response to the burning candle question.
Table 6 Percentages of students who used each rule in the beryllium oxide, symbolic beryllium oxide, unknown chemical, and burning candle contexts. Many students who chose answer choices a , b , and d — all consistent with the use of a combustion rule — gave no reasoning. Thus, we hypothesize that the percentages of students using a combustion rule, as well as the percentages of students who provided explicit conservation reasoning, are underestimates.
The products can only have whatever is in the reactant so beryllium oxide would be the only possible product from the list. Burning something involves adding oxygen so c is best fit, and it's also balanced. Therefore, less O 2 will be in the air over time. This is because water and carbon dioxide are made up of carbon, hydrogen, and oxygen. The oxygen comes from the air as O 2.
However, the carbon and the Hydrogen must come from one of the reactants. Both wood and butane have carbon and hydrogen in them so they could have been burned. Whenever there is combustion involved, it will produce CO 2. Beryllium can't be completely gone so beryllium oxide could result since there is gas involved and is released. There is hydrogen in the air, so we know it is a reactant. Although impurities exist in fossil fuels, hydrocarbon combustion is the primary process in the burning of fossil fuel.
An example of hydrocarbon combustion is illustrated in Figure 1. See simulation at the bottom of the page for more examples. Regardless of the type of hydrocarbon, combustion with oxygen produces 3 products: carbon dioxide, water and heat, as shown in the general reaction below.
The energy required to break the bonds in the hydrocarbon molecules is substantially less than the energy released in the formation of the bonds in the CO 2 and H 2 O molecules. For this reason, the process releases significant amounts of thermal energy heat. This thermal energy can be used directly perhaps to heat a home or else it can be converted to mechanical energy, using a heat engine.
However, this is subject to efficiency losses, resulting in necessary significant energy losses as waste heat governed by the second law of thermodynamics. The resulting useful mechanical energy will be a lot less than the initial thermal energy provided by the hydrocarbon combustion.
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