Chemistry
Physical Properties of Alcohol
The physical properties of alcohol include its colorless and flammable nature, as well as its characteristic odor. It has a lower boiling point compared to water, making it evaporate more quickly. Additionally, alcohol is miscible with water, meaning it can mix with water in any proportion.
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4 Key excerpts on "Physical Properties of Alcohol"
eBook - ePub- Des W. Connell(Author)
- 2005(Publication Date)
- CRC Press(Publisher)
Part IIBasic Properties of Chemicals in the Environment
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2 Bonds and Molecules: Their Influence on Physical-Chemical Properties in the Environment
2.1 INTRODUCTIONThe behavior of chemicals in the environment is governed by their physical-chemical properties as well as transformation and degradation processes, which are discussed in Chapter 3 . The physical-chemical properties of compounds include such characteristics as boiling point (bp), melting point (mp), solubility in water, and similar properties. These properties are, in fact, measurements made in the laboratory of environmentally relevant characteristics. For example, compounds with low boiling points evaporate rapidly into the atmosphere, whereas compounds that are highly soluble in water disperse readily in streams and rivers. Thus, an understanding of these properties would be expected to give a clearer perception of how compounds will behave in the environment. This means that the measurement of the physical-chemical properties of a compound could be used to provide an evaluation of its environmental distribution in air, water, sediments, soil, and animals.2.2 STATES OF MATTER IN THE ENVIRONMENTA cursory examination of the nature of our environment reveals that matter exists in basically three states: solid, liquid, and gas. Solids are present as soil, rocks, and so on, whereas liquids are represented by the great water bodies of the oceans, lakes, and rivers. The gaseous component of the environment is the atmosphere. These states exercise a basic influence on the nature and distribution of all substances, both natural and man-made, in the environment in basic chemical terms. Solids have a definite volume and shape and consist of large numbers of particles that could be atoms, ions, or molecules (Figure 2.1
eBook - PDF- Satinder Ahuja, Neil Jespersen(Authors)
- 2006(Publication Date)
- Elsevier Science(Publisher)
Chapter 3 Evaluation of basic physical properties Neil Jespersen 3.1 INTRODUCTION Some of the simplest techniques and instruments are valuable tools for chemical analysis. This chapter is designed to remind students that simple, rapid methods are advantageous in many situations. These methods are often used for quality control purposes. The methods dis-cussed here are melting and boiling points, viscosity, density or specific gravity and refractive index. Time is often an important consideration in practical chemical ana-lysis. Raw materials awaiting delivery in tanker trucks or tractor-trailers often must be approved before they are offloaded. Batches of product prepared by compounders on the factory floor must be analyzed and approved before the packaging process can begin. Analysis is often per-formed again on packaged products before they are sent to the ware-house. To maintain a smoothly running manufacturing system, the analytical chemist must have rapid, informative methods to assay a wide variety of samples. Also important in quality control is the establishment of standards that are agreed upon by all involved in the manufacturing process. Lax enforcement of standards brings into question the utility of the analysis and threatens product quality. Observation and measurement of physical properties are the oldest known means of assessing chemical purity and establishing identity. Their utility comes from the fact that the vast majority of chemical compounds have unique values for their melting points, boiling points, density and refractive index. In addition, viscosity and conductance are rapid methods for overall properties of substances. The Handbook of Chemistry and Physics has approximately 100 tables listing the refrac-tive index, density, specific gravity, viscosity and conductivity of aque-ous solutions of common inorganic and organic solutes at varying concentrations.
- Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
22.4 CHEMICAL PROPERTIES OF ALCOHOLS Write equations to illustrate the typical reactions of alcohols. An alcohol contains the hydroxyl functional group ( i OH). Chemists have chosen the term functional group to indicate that this group brings a “function” to an organic molecule. Just as adding new electronic chips to a calculator adds new functions, attaching a hydroxyl group to an alkyl chain allows a molecule to function in new ways. As we have seen, the i OH group interacts with water so that when a molecule adds a hydroxyl group, its solubility in water increases. In general, the “functions” of a hydroxyl group help determine the properties of an alcohol. Acidic and Basic Properties Aliphatic alcohols are similar to water in their acidic/basic properties. If an alcohol is mixed with a strong acid, it will accept a proton (act as a Brønsted–Lowry base) to form a protonated alcohol or oxonium ion: CH 3 OH � H 2 SO 4 CH 3 O � H H � HSO 4 � Alcohols also can act as Brønsted–Lowry acids. Methanol and ethanol have approximately the same acid strength as water, while the larger alcohols are weaker acids than water, reflecting the properties of the longer alkanelike carbon chains. Both water and alcohols react with alkali metals to release hydrogen gas and an anion: sodium hydroxide H 2 O � 2 Na 2 Na � 2 � OH � H 2 sodium ethoxide CH 3 CH 2 OH � 2 Na 2 Na � 2 � OCH 2 CH 3 � H 2 (g) (g) KEY TERMS oxonium ion alkoxide ion Saytzeff’s rule condensation reaction LEARNING OBJECTIVE 22.4 • Chemical Properties of Alcohols 545 The resulting anion in the alcohol reaction is known as an alkoxide ion (RO - ). Alkoxides are strong bases (stronger than hydroxide), and so they are used in organic chemistry when a strong base is required in a nonaqueous solution. The order of reactivity of alcohols with sodium or potassium is primary 7 secondary 7 tertiary. Alcohols do not react with sodium as vigorously as water.
eBook - ePubBrewing Materials and Processes
A Practical Approach to Beer Excellence
- Charles W Bamforth, Charles Bamforth, Charles W. Bamforth(Authors)
- 2016(Publication Date)
- Academic Press(Publisher)
Alcoholic strength is the term used to denote the measure of the amount of ethyl alcohol (ethanol) in beer. It may be reported as percent by mass of beer (% weight/weight—w/w or mass/mass—m/m) or as percent by volume (% volume/volume—v/v). These values are expressed at either 15.56°C (60°F) or at 20°C (68°F) depending on country, regulatory authority, or other local requirements.The analysis of beer for alcohol content is important both for quality assurance programs and for legal reporting purposes. Results, however, are subject to appreciable variation and the analyses are often time-consuming and expensive. Over 180 years of research, laboratory practice, and a number of established verified tables of data and extensive algorithms help the brewing chemist best determine alcohol content in beer. In fact, up until about 40–50 years ago many brewers would have fielded out their samples to one of the major brewing institutes available to serve their research functions and analytical testing needs. These institutes were the ones actively engaged in the research that led to many of the methods officially adopted back then, many of which are still in use today. Such methods have evolved through new technological developments with modern instrumentation now simplifying the measurement of alcohol by brewers in their own facilities. That said, the grounding principles and theories behind alcohol determinations remain largely unmodified since their discovery, as will be demonstrated.The Properties of Alcohol and Their Measurement
Ethanol is miscible with water in all proportions, with ethanol molecules fitting within the “spaces” in the three-dimensional structure of water. This “space filling” property means that the final volume of any mixture of water and alcohol is less than the sum of their individual volumes, ie, volume contraction occurs upon mixing (Hu et al., 2010 ; Meija, 2009 ). This volume contraction has to be accounted for when determining alcohol by volume in aqueous mixtures. Solution volumes are temperature dependent and so temperature compensation has to be allowed for in measurements. Brewers using hydrometers are aware of this with the need to obtain the actual temperature and consult instrument manufacturer's tables to make density or specific gravity measurement adjustments. Increasingly sophisticated instrumentation compensates for temperatures of measurement and can deliver reportable data at specified temperatures. In the United States, alcohol by volume is sometimes still reported at 15.56°C (60°F), though more frequently 20°C (68°F) is the required temperature. The temperature volume change is effectively so small between these two temperatures that the difference for most beers in the range of 3.5–8% alcohol by volume is only 0.02–0.03%. The lower value here is at 15.56°C (60°F). Given this small range, and because the Alcohol and Tobacco Tax and Trade Bureau (TTB) in the United States allows ± 0.3% alcohol by volume tolerance in beer measurements, it is unclear why some authorities are still adamant on the 15.56°C (60°F) recorded value. Early alcohol tables were generated based on determinations made at 15.56°C (60°F) and are still available as needed [Association of Official Analytical Chemists (AOAC, 1995
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