Comparing the enthalpy changes of combustion ofdifferent alcohols.
Comparing the enthalpy changes of combustion of different alcohols. What are alcohols? Alcohol is the common family name for the hydrocarbon group alkanols. At least one of the hydrogen groups is replaced by an -OH group. They are all organic compounds. The general formulas for the alcohols are: CnH(2n+1)OH Where n represents a number. The first and simplest member of the alkanols family is methanol. Its molecular formula is CH3OH. You can now see that each member of the alcohol family has a different number of carbons in its structure. They increase by one carbon atom and two hydrogen atoms each time. The question that this piece of coursework is going to answer is "Is there a relationship between the number of carbon atoms in a chain and the enthalpy change of combustion?" Aim The aim of this experiment is to prove that the longer the hydrocarbon chain the higher the amount of energy transferred to the water, therefore fewer moles of fuel will be used to achieve a temperature rise of 15°C. The enthalpy change of combustion is the amount of energy transferred when one mole of a substance burns completely in oxygen (always -ve). To work out the enthalpy change of combustion of the alcohols the energy output must be measured. The easiest way to do this accurately is to use the thermal energy of combustion to raise the temperature of a substance with a known
What an ester is, how it is made, examples of esters, animal testing issues and ethics.
Using esters in cosmetics Esters are used regularly and are in many of our everyday cosmetic products, drinks, foods etc. The most They provide an artificial smell or flavouring and provide a wide range of smells and tastes (depending on the type of carboxylic acid used). A lot of people would not have heard about esters, thus, they would also not know many important ingredients in the cosmetics they buy. Many products test on animals which many people would find unethical. We were investing at school esters and how to make an ester, also, we looked further into the unknown ingredients we may find in our products and how many people would but things and not know if it was animal tested or not . In this essay I will write about: what an ester is, how it is made (the experiment I carried out to make an ester), examples of esters, animal testing issues and ethics, a questionnaire I carried out to see what people knew about the cosmetics they own, what an emollient is and I will write about a fair test that I can carry out to see if the cosmetics are right about the information they give about their cosmetics- to the general public. (http://www.myhealthguardian.com/wp-content/uploads/2009/10/cosmetics-070126-1-full.jpg ) So what are cosmetics? The US Food and Drug Administration believe that cosmetics are "articles intended to be rubbed, poured, sprinkled, or sprayed on,
The aim of this investigation is to compare the enthalpy of the following different fuels:Ø Methanol - CH3OHØ Ethanol - C2H5OHØ Propanol - C3H7OHØ Pentanol - C5H11OH
Aim: The aim of this investigation is to compare the enthalpy of the following different fuels: > Methanol - CH3OH > Ethanol - C2H5OH > Propanol - C3H7OH > Pentanol - C5H11OH Background Information Crude oil (petroleum) is our main source of food and organic (carbon-based) chemicals. Crude oil is a thick, smelly, dark brown liquid. It is a mixture of hundreds of compounds. These vary from simple substances like methane (CH4) to complex substances with dozens of atoms per molecule. Most of the compounds in crude oil are hydrocarbons. Crude oil itself is useless. It must be separated into different fractions before it is used. Each fraction contains a mixture of hydrocarbons with similar properties. Some of the fractions contain volatile hydrocarbons, which are easily vaporized. These fractions can be used as petrol. Other fractions are much less volatile. They can be used as fuel for ships and power stations. A furnace first heats the crude oil and the vapours pass into the lower part of the fractionating column. As the vapours rise up the column through holes in the trays, the temperature falls. Vapours of different compounds condense at different heights in the column as the temperature falls below their boiling points. Liquids such as petrol (gasoline), which boil at low temperatures, condense high up the column. Liquids such as diesel oil, which boil at high
THE LINK BETWEEN CARBON ATOMS IN A FUEL AND THE ENERGY IT RELEASES.
CHEMISTRY COURSEWORK THE LINK BETWEEN CARBON ATOMS IN A FUEL AND THE ENERGY IT RELEASES. PLANNING INTRODUCTION Alcohols generally belong to compounds whose molecules are based on chains of carbon atoms. They usually contain one oxygen atom, which is joined to a carbon atom by a singular bond. This makes them different to other compounds. The oxygen atom is joined to the hydrogen atom as well as the carbon atom, which makes the oxygen a part of a hydroxyl group. These atoms are generally a part of a hydrocarbon chain. These alcohols can take away water from the body, in which a hydrocarbon chain has replaced a hydrogen atom. Alcohols have a general structure of CnH2n+1OH The aim of this investigation is to see the link between the numbers of carbon atom in a fuel with the amount of energy it releases. There would be a change in the amount of energy given off that is getting greater, the more carbon atoms in the fuel, the more there are more bonds to be broken and formed, thus producing more energy. 'In a chemical reaction, bonds in the reactant molecule are broken and new ones are formed. Atoms are rearranged. Energy has to be put in to break bonds, and energy is given out when bonds are formed.' When the total energy put in is greater than the energy put out, the substance cools down (it is endothermic). This is expressed as ? +ve (delta positive). If the total energy put
Investigating the energy released from burning different alcohols.
Investigating the energy released from burning different alcohols Alcohols burn and react with oxygen forming water and carbon dioxide; the equations below show the reactions between oxygen and 8 alcohols from methanol to ethanol. For these reactions to start, energy is required to break the existing bonds between the atoms of molecules of the reactants. For example in methanol, C-H bonds, C-O bond and O-H bonds and O=O double bonds need to be broken, energy is required to break these bonds as well as others in the reaction. However when new bonds are formed between atoms at the end of the reaction: C=O double bonds as well as O-H bonds are formed and as they are formed they release energy. As the energy released from the new bonds formed is more than the energy required to break the old bonds, the reaction is exothermic, overall it release energy into the surroundings. The aim of this investigation is to find out how the energy released from the different alcohols differs. Hypothesis My hypothesis is based upon the theoretical values of the different heats of combustion of the alcohols. Each will be different as different number of bonds will be broken and different number of bonds will be made, although in each case all of the bonds broken and made will be the same for each alcohol. Alcohol Theoretical Values (kJ/mol) Methanol -656.5 Ethanol -1272 Propanol
Comparing the Enthalpy Changes of Combustion of Different Alcohols
Chemistry Coursework: Comparing the Enthalpy Changes of Combustion of Different Alcohols Background The enthalpy (energy) change of combustion, or as it is known in its shortened form ?Hc is the enthalpy change that occurs when 1 mole of a fuel is burned completely in oxygen. For standard enthalpy change of combustion to take place the fuel needs to be burned in standard conditions i.e. 1 atmosphere pressure and 298K. Of course this is more theoretical as carrying out a combustion experiment without any heat loss is very difficult. In the experiment I am carrying out I will not be able to achieve standard conditions for combustion due to limitations with equipment. A way of minimising the heat loss during an experiment to measure the enthalpy change of combustion is by using a bomb calorimeter to maximise the amount of heat trapped during the combustion and afterwards. Below: Diagram of a bomb calorimeter: 1) Stirrer 2) Calorimeter bomb 3) Jacket 4) Calorimeter vessel 5) Thermometer 6) Ignition lead 7) Jacket lid By using a bomb calorimeter it allows for accurate measurements of energy changes of combustion. Fuel inside a bomb calorimeter is ignited electrically and burns the oxygen inside a pressurised container, as can be seen in the diagram. The energy from the combustion of the fuel is transferred to water surrounding the pressurised container and the
The Abacus: A History
The Abacus: A History How did people keep track of numbers before pen and paper were widely available? How does addition and subtraction work if you don't have a handy written form for your numbers? Say you can't read or write, but you can count - how do you add, subtract, multiply, or divide large numbers? The answer to all these questions is . . . the abacus! What is an abacus? An abacus is a device used for addition and subtraction, and the related operations of multiplication and division. It does not require the use of pen and paper, and it's good for any base number system. There are two basic forms for the abacus: a specially marked flat surface used with counters (counting table), or a frame with beads strung on wires (bead frame). Timeline of the Abacus Chinese Abacus ************************************* Japanese Abacus *************************** Aztec Abacus ******* Counting Table ****************************************** 600 BC 500 BC 0 900 AD 1600 AD 1826 AD 1999 AD The Counting Table Although counting tables are obsolete now, they have over 2000 years of documented use. Their earliest form was that of a simple stone slab with incised parallel lines. The lines served to mark the place values. The earliest known counting table is from the island of Salamis in
An Investigation into the Enthalpies of the Combustion of Alcohols.
An Investigation into the Enthalpies of the Combustion of Alcohols Planning My aim for this experiment is to see the energy produced from different alcohols. This investigation involves burning alcohol in the air. 'GCSE Chemistry' by B.Earl and L.D.R Wilford says that "alcohols form, another homologous series, with the general formula Cn H2n+1OH ". The alcohol reacts with the oxygen in the air to form the products water and carbon dioxide. This reaction is exothermic, as heat is given out. This is because the amount reactant energy is more than the product energy the difference between this is ?H, therefore some energy has been given out in the form of heat. The energy is given out when forming the bonds between the new water and carbon dioxide molecules. This can be shown in an energy level diagram: Reaction co-ordinate ?H is the heat content, which is the enthalpy, which is negative in exothermic reactions as the diagram shows that energy is 'lost' as heat. Enthalpy is defined as the energy of reaction, or the heat energy associated with a chemical change. For any reaction carried out directly at a constant pressure, the heat flow is exactly equal to the difference between enthalpy of products and that of the reactants. To measure the heat energy given off, we must use this energy to heat something, this will be water. This is assuming that all the heat produced by
'Enthalpy of Combustion'.
Planning Alcohols are very similar to alkanes and alkenes; they are a family of related compounds - a homologous series. Each member of the series has the O-H group in its molecule. The general formulas for alcohols is Cn H2n+1 OH, where n is the number of carbon atoms. There are six alcohols that I will be using and they are Methanol (CH3OH), Ethanol (CH2H5OH), Propan-1-ol (C3H7OH), Butan-1-ol (C4H9OH), Pentan-1-ol (C5H11OH) and Octan-1-ol (C8H17OH). In this experiment I will be burning a range of alcohol's to heat up a container of water. I will be trying to get reliable results that will tell me how the number of carbon atoms relate to the energy released as heat , otherwise known as the 'Enthalpy of Combustion'. The combustion process is the making and breaking of bonds. In this experiment, the alcohols will have an exothermic reaction because heat is given out. The breaking of bonds is endothermic and the making of bonds is exothermic. In an exothermic reaction the products are at a lower energy level than the reactants, the difference is the heat energy. The energy is given out when forming the bonds between the new water and the carbon dioxide molecules. The complete combustion of an alcohol is when it reacts with oxygen in the air to form water and carbon dioxide. The basic formula for this reaction is Heat Transferred = Mass of Substance (g) x Temperature Change
Investigate the different amounts of energy given off when different alcohols are combusted. I will be using the alcohols of methanol, ethanol, propanol, butanol and pentanol.
TO FIND THE ENTHALPY OF THE COMBUSTION OF DIFFERENT ALCOHOLS PLANNING C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H2O(l) (Alcohol + Oxygen --> Carbon Dioxide + Water) Aim: I am going to investigate the different amounts of energy given off when different alcohols are combusted. I will be using the alcohols of methanol, ethanol, propanol, butanol and pentanol. Safety note: In this experiment I will be dealing with Bunsen burners and the heating of alcohols. For this reason I wore safety goggles and I was very careful when handling the alcohols as they can be very dangerous. Variables: Independent Variable: Type of alcohol Dependent Variable: Temperature rise of the water Fixed Variables: Volume of water (100cm3), length of time to heat water (2 mins), length between the wick burner and the beaker of water(5cm). Apparatus: . Five different alcohol liquids (Methanol; Ethanol; Propanol; Butanol; Pentanol) 2. Alcohol burners, contains with a wick down the centre so that the liquid can soak up. These were already set out by the technicians with the correct alcohol liquids before hand. 3. Calorimeter (thermometer and a tin)I will be using a copper can for this experiment 4. Stopwatch 5. 100cm3 measuring cylinder 6. Electric balance 7. Heat mat and safety goggles Diagram: Method: I set up the apparatus as show in the diagram * I measured out 100cm3 of water with a
