Name: boiling point and vapor pressure
Uploaded: 2020-03-26T07:22:27.000Z
Duration: 4 min 25 s
Channel: JoVE

K12 Standards

Georgia Standards of Excellence

9-12

Physical Science

SPS2.

Physical Properties

Boiling Points

액체는 분자 간의 약한 상호 작용에 의해 함께 유지됩니다. 기체 상태로 전환하려면 분자가 이러한 상호 작용을 극복하기 위해 열 또는 기타 소스로부터 충분한 에너지를 얻어야 합니다.
실온에서 순수한 액체의 밀폐 된 용기를 생각해 봅시다. 표면의 액상 분자 중 일부는 증발하기에 충분한 에너지를 얻고 그 증기 중 일부는 에너지를 잃고 액체로 다시 응축됩니다. 증발과 응축 속도가 같을 때 액체와 증기는 평형에 도달합니다. 이 시점에서 액체 위의 공간은 증기로 포화되고 용기의 액체 및 증기의 양에는 순 변화가 없습니다. 증기에 의해 가해지는 압력을 증기압이라고 합니다.
이제 열린 액체 용기를 생각해 보십시오. 여기서 증기가 빠져나갈 수 있어 액체 위의 영역이 포화되는 것을 방지할 수 있습니다. 따라서 액체가 남지 않을 때까지 증발이 계속될 수 있습니다. 액체의 온도가 증가함에 따라 증발 속도도 증가하고 증기압도 증가합니다. 충분한 열이 가해지면 액체 속의 더 깊은 분자가 기화하기 시작하며, 이를 통해 증기 거품이 형성되는 것을 볼 수 있습니다.
이것을 끓는 것이라고하며 화합물의 증기압이 대기압과 같을 때 시작됩니다. 이것이 발생하는 온도가 끓는점입니다. 각 순수 물질은 분자간 상호 작용의 유형과 강도가 다르기 때문에 다른 물질은 끓는점이 다릅니다.
이제 분자간 상호 작용이 끓는점에 어떤 영향을 미치는지 살펴보겠습니다. 많은 분자간 상호 작용에는 쌍극자라고 하는 고르지 않은 전자 밀도가 있는 영역이 포함됩니다. 모든 분자는 전자 분포에 짧은 변동이 있으므로 비극성 분자도 일시적으로 쌍극자를 가질 수 있습니다. 이에 대한 응답으로 반대 쌍극자가 근처 분자에서 형성됩니다.
일시적 쌍극자와 유도 쌍극자 사이의 인력을 런던 분산력이라고 하며, 탄화수소와 같은 비극성 분자 간의 지배적인 상호 작용입니다. 런던 분산력은 전자가 많은 큰 분자 사이에서 더 강한데, 그 이유는 이러한 분자가 전자를 약하게 유지하여 이웃 분자가 전자 분포에 더 쉽게 영향을 미치기 때문입니다.
예를 들어, 고분자량 비분지형 알칸은 저분자량 비분지형 알칸보다 끓는점이 높습니다. 게다가, unbranched alkane에는 그것의 더 높은 표면적 때문에 비슷하게 분자량을 가진 분지형 alkane 보다는 더 높은 boiling 점이 있습니다.
극성 결합이 있는 분자는 영구 쌍극자를 가지고 있어 이들 간의 규칙적인 쌍극자-쌍극자 상호 작용을 가능하게 합니다. 쌍극자-쌍극자 상호 작용은 런던 분산력보다 강하기 때문에 일반적으로 비극성 액체보다 극성 액체를 끓이는 데 더 많은 열 에너지가 필요합니다. 예를 들어, 극성 분자인 클로로펜탄 1개의 끓는점은 108°C입니다. 표면적이 비슷하지만 쌍극자가 없는 헥산은 끓는점이 더 낮습니다.
전기 음성도가 더 높은 원자에 공유 결합된 수소와 고독한 전자 쌍을 가진 전자 인출 원자를 모두 가진 분자는 수소 결합이 가능합니다. 수소 결합은 쌍극자-쌍극자 상호 작용 및 런던 분산력보다 강하기 때문에 이를 극복하려면 훨씬 더 많은 열 에너지가 필요합니다. 예를 들어, 프로판과 에탄올은 분자량과 표면적이 비슷합니다. 그러나 프로판의 끓는점은 에탄올 분자가 서로 수소 결합을 형성할 수 있지만 프로판은 그렇지 않기 때문에 에탄올보다 훨씬 낮습니다.
이 실험실에서는 모세관 방법을 사용하여 두 가지 유기 용매의 끓는점을 측정합니다.

끓는점

끓는점 측정
녹는점과 유사하게, 끓는점은 물리적 특성입니다. 샘플이 순수한 화합물인 경우 끓는점을 사용하여 화합물의 정체를 결정할 수 있습니다. 궁극적으로 정확한 끓는점을 실험적으로 결정하는 것은 어려운 일입니다. 녹는점과 마찬가지로 실험적 끓는점은 범위로 제공되며 실제 문헌 값에서 몇 도 정도 다릅니다.
증기압
용액의 익숙한 버블링을 특징으로 하는 용매가 끓는 이유를 이해하려면 액체상과 기체상 사이의 역학을 이해하는 것이 중요합니다. 밀폐된 용기에 담긴 순수한 액체 화합물을 생각해 보십시오. 액체 표면의 일부 분자는 분자간 힘을 극복하고 기체 상태로 들어갈 수 있는 충분한 에너지를 가지고 있습니다. 그러나 기체 상태의 분자는 에너지를 잃고 액체로 다시 응축될 수도 있습니다. 따라서 이 시스템에는 증발과 응축이라는 두 가지 경쟁 과정이 있습니다.
증발 속도가 응축 속도와 같을 때 시스템은 평형 상태에 도달한 것입니다. 이는 기체 상태로 들어가는 모든 분자에 대해 다른 분자가 액체 상태로 응축되고 용기 내 액체 또는 기체 양의 순 이득 또는 손실이 없음을 의미합니다. 일단 평형이 확립되면 액체 위의 증기에 의해 가해지는 압력을 증기 압력이라고 합니다. 액체가 기화하는 경향을 휘발성이라고 합니다. 휘발성이 높은 액체는 증기압이 더 높고 휘발성이 낮은 액체는 증기압이 낮습니다.
증기압은 온도에 따라 다릅니다. 용액의 온도를 높이면 더 많은 분자가 액상을 빠져나갈 수 있는 충분한 에너지를 갖게 되므로 증기압이 증가합니다. 궁극적으로 충분한 열이 가해지면 액체와 기체 사이의 경계면에 있지 않은 분자가 기체 상태로 전환되어 끓는 것과 관련된 친숙한 거품을 형성합니다.
액체의 끓는점은 액체의 총 증기압이 대기압과 같을 때 도달합니다. 이것이 발생하는 온도를 끓는점이라고 합니다. 더 높은 고도에서 따라서 더 낮은 대기압에서는 증기압을 대기압으로 증가시키는 데 더 적은 열이 필요하기 때문에 액체는 더 낮은 온도에서 끓습니다. 또한 휘발성 또는 용매가 기화하는 능력도 증기압에 영향을 미칩니다. 휘발성이 높은 용매는 휘발성이 낮은 용매보다 증기압이 높습니다.
끓는점에 영향을 미치는 요인
융점과 끓는점 사이의 유사성은 화합물의 융점에 영향을 미치는 동일한 요인이 끓는점에도 영향을 미친다는 것을 의미합니다. 따라서 액체 화합물 내에서 발견되는 분자간 힘의 강도와 유형은 끓는점에 영향을 미칩니다. 분자력에는 수소 결합, 쌍극자-쌍극자 상호 작용 및 런던 분산력의 세 가지 유형이 있음을 기억하십시오. 이들 각각은 서로 다른 인력 강도를 가지고 있으며 극복하기 위해 다른 양의 에너지를 필요로 합니다. 수소 결합이 가능한 화합물은 런던 분산력을 통해서만 상호 작용할 수 있는 화합물보다 끓는점이 더 높습니다. 끓는점에 대한 추가 고려 사항은 화합물의 증기압 및 휘발성과 관련이 있습니다. 일반적으로 화합물의 휘발성이 높을수록 끓는점이 낮아집니다.
끓는점을 측정하는 모세관 방법
유기 화합물의 끓는점을 측정하는 간단한 방법은 모세관 방법을 사용하는 것입니다. 이 설정에서는 빈 유리 모세관이 액상의 순수 화합물 용기로 반전됩니다. 액체가 가열되면 샘플의 증기압이 증가하고 기체 증기가 유리 모세관으로 들어가기 시작합니다. 이로 인해 내부에 갇힌 공기가 빠져나가고 모세관 바닥에서 기포가 생깁니다. 이 시점에서 액체는 냉각됩니다. 샘플의 증기압이 유리 모세관 내부의 대기압과 같으면 액체가 튜브로 들어가기 시작합니다. 이 현상이 발생할 때 용액의 온도는 액체 화합물의 끓는점입니다.

끓는점 측정
녹는점과 유사하게, 끓는점은 물리적 특성입니다. 샘플이 순수한 화합물이면 끓는 ...

Education

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JoVE Lab Manual

Chemistry

화학

boiling point and vapor pressure

Boiling point and vapor pressure are key physical properties of a liquid. For a pure compound, the boiling point can help identify the substance. In experiments, the boiling point is usually recorded as a range because exact values are hard to measure and may differ by a few degrees from the literature value.

Vapor pressure explains why a liquid boils. In a sealed container, some molecules at the liquid surface gain enough energy to escape into the gas phase. At the same time, some gas molecules lose energy and condense back into the liquid. When evaporation and condensation happen at the same rate, the system is at equilibrium. The pressure from the vapor above the liquid is the vapor pressure.

Volatility is the tendency of a liquid to vaporize. A more volatile liquid has a higher vapor pressure, while a less volatile liquid has a lower vapor pressure. Vapor pressure also changes with temperature. As temperature rises, more molecules can escape the liquid, so vapor pressure increases. With enough heat, molecules inside the liquid also change to gas and form the bubbles seen during boiling.

A liquid boils when its total vapor pressure matches atmospheric pressure. That temperature is the boiling point. Because atmospheric pressure changes with elevation, a liquid boils at a lower temperature at higher elevations. Less atmospheric pressure means less heat is needed for the vapor pressure to reach that level.

Intermolecular forces also affect boiling point. These forces include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. They differ in strength, so different amounts of energy are needed to overcome them. Compounds that can hydrogen bond usually have higher boiling points than compounds that rely only on London dispersion forces. Volatility matters too. In general, more volatile compounds have lower boiling points.

One simple way to measure a boiling point is the capillary method. An empty glass capillary tube is placed upside down in the liquid sample. As the sample is heated, its vapor pressure rises and vapor enters the tube. This pushes out trapped air and causes bubbles to appear from the bottom of the capillary tube. The sample is then allowed to cool. When liquid begins to rise into the tube, the vapor pressure inside the tube matches the atmospheric pressure. The temperature at that moment is the boiling point of the compound.

Boiling Point and Vapor Pressure

lab techniques

Measuring with Accuracy in the Lab

Measuring with accuracy in the lab starts with careful records, the right tools, and correct reading of data. Scientists use lab notebooks to record how an experiment was done. These notes include the amounts of materials used and each step of the procedure. Without that record, an experiment cannot be repeated in the same way. Balances and glassware are used to measure solids and liquids for experiments. The precision of a measurement depends on the equipment used. Digital balances show the...

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Graphs, Curve Fit, and Standard Deviation

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stoichiometry, product yield, and limiting reactants

stoichiometry-product-yield-and-limiting-reactants

Balancing Equations and Reactant Limits

Chemical equations show how reactants change into products during a reaction. Stoichiometry is the study of the relative amounts of reactants and products. It is based on the Law of Conservation of Mass, which says matter is neither created nor destroyed. Because atoms are only rearranged, the number and identity of atoms must match on both sides of a reaction. That is why a chemical equation must be balanced. A balanced equation has the same number of atoms for each element in the reactants...

redox reactions

Oxidation States in Redox Reactions

Oxidation states help identify redox reactions. In a redox reaction, oxidation is the loss of one or more electrons, and reduction is the gain of one or more electrons. These reactions are often tracked by changes in oxidation state, also called oxidation number. Each atom in a molecule has an oxidation state. This number shows how oxidized an atom is compared with its free elemental form. It is written as the charge an atom would have if every bond were purely ionic. In that model, bonding...

ideal gas law

Gas Laws Behind the Ideal Gas Equation

The ideal gas equation brings together the main gas laws used in chemistry. Gases have molecules that are far apart, so their behavior is described with four measurable variables: pressure, volume, number of moles, and temperature. The ideal gas law links these variables with the gas constant, R, which equals 8.314 J·K−1 mol−1. Boyle’s law describes the link between pressure and volume. When temperature and the number of moles stay constant, pressure and volume change in opposite directions.

acid and base concentrations

Acids, Bases, and pH in Titration

Acids, bases, and pH explain how acidic or basic a solution is. An Arrhenius acid releases hydrogen ions when it dissolves in water, while an Arrhenius base releases hydroxide ions. These reactions also create conjugate partners: an acid forms a conjugate base after losing hydrogen, and a base forms a conjugate acid after losing hydroxyl. Every acid has a conjugate base, and every base has a conjugate acid. pH measures the amount of hydrogen ions in a solution. The pH scale runs from 0 to 14...

buffers

Buffer pH and the Common Ion Effect

Buffer solutions help keep pH steady when acids or bases are added. In water, an Arrhenius acid (HA) dissociates into hydrogen ions, H+, and a conjugate base, A-. More hydrogen ions make a solution more acidic and lower its pH. An Arrhenius base (BOH) dissociates into a conjugate acid, B+, and hydroxide ions, OH-. Strong acids and strong bases usually change pH a lot because they react completely in water and raise the amount of H+ or OH-. Buffers reduce those pH changes. A buffer usually...

enthalpy of reaction

Reaction Heat, Hess’s Law, and Calorimetry

Reaction heat is explained through enthalpy, Hess’s law, and calorimetry. These ideas show how heat moves during chemical reactions and how scientists measure it. Thermodynamics is the study of heat energy and other forms of energy, such as work. Its laws are used across science, from biology to physics. The first law says energy is conserved in an isolated system. Energy can change form, such as thermal energy becoming work, but it cannot be created or destroyed. The second law of...

solubility

Solubility in Water and Other Solvents

Solubility describes how much of a solute can dissolve in a specific solvent. It is usually reported as solute mass per solvent volume or as solute mass per solvent mass. For example, sodium chloride has a solubility of 36 g per 100 mL of water at room temperature. If solubility is given by solvent mass, that mass must be converted to volume for later calculations. Temperature changes solubility. Sodium carbonate dissolves at about 7 g per 100 mL of water at 0 °C, 22 g per 100 mL at room...

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Flame Test Metal Color Clues

Flame testing uses a metal sample and a flame to identify a substance by its color. Each element gives off a characteristic light emission in the flame, so the color can help distinguish one element from another. This same idea appears in fireworks, where different metal components create different colors. The color comes from energy absorbed by the metallic component. When a species absorbs energy, that energy can go into translation, vibration, rotation, or electron excitement. Electron...

balmer series

Hydrogen Emission Lines

Hydrogen emission lines show how electrons move between fixed energy levels in the Bohr model. Niels Bohr proposed this model for the hydrogen atom in 1913. In this model, an electron can only occupy certain orbits, and it cannot exist between them. These energy states are labeled with the quantum number n. The ground state is n = 1. Higher values, such as n = 2, 3, 4, and so on, are excited states. An electron changes state only by absorbing or emitting energy equal to the difference between...

beer's law

Absorbance Spectra and Beer-Lambert Analysis

Absorbance spectra and the Beer-Lambert Law show how light can be used to study molecules in solution. When light hits a substance, it may be absorbed, transmitted, or reflected. A substance often interacts with a range of wavelengths, and each wavelength can affect the molecules or atoms in a different way. When a molecule absorbs light, that energy can be used for translation, vibration, rotation, or electron excitement. Electron excitement is especially important in spectroscopy because it...

concentration dependence

Reaction Order and Rate Constants

Chemical kinetics describes the speed of a chemical reaction. The rate depends on the reaction mechanism, the complexity of the reaction, and the number of reactants involved. Reactant concentration also affects how fast a reaction happens. The rate law is the experimental relationship that connects these factors to reaction rate. In the rate law, each reactant contributes through a reaction order. The general form is r = k[A]^m[B]^n for aA + bB + ... → cC. Here, r is the reaction rate, k is...

temperature dependence

Reaction Rate, Arrhenius, and Catalysts

Chemical kinetics explains how fast a reaction happens and why that speed changes. The reaction rate is the speed of a chemical reaction. It is defined as the change in concentration of a reactant or product over time. Reaction speed depends on several factors, including the concentration of the reactants and the temperature of the reaction. Each reactant affects the rate in a specific way. That relationship is described by the rate law. The rate law is an equation that connects the...

galvanic cells

Battery Power from Redox Reactions

Electrochemistry studies how chemical change and electrical energy are linked. In this branch of chemistry, electrons move from one species to another. That movement can either produce current or be driven by an applied current. The main reaction in electrochemistry is the oxidation-reduction, or redox, reaction. A redox reaction has two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. These changes also shift the oxidation state of each substance. The...

electrolytic cells

Electroplating with Electrolytic Cells

Electrochemistry links electrical energy with chemical change, and electrolytic cells show how electricity can drive a nonspontaneous reaction. In these reactions, electrons move from one species to another. The key chemistry is a redox reaction, or oxidation-reduction reaction, which happens in two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. The substance that loses electrons is the reducing agent, and the substance that gains electrons is the...

proper lab notebook keeping

Recording a Reproducible Lab Experiment

Accurate lab notebook records are essential in science and organic chemistry labs. Without clear notes, descriptions, quantities, and observations, an experiment cannot be repeated or checked. Good record keeping supports reproducibility, which means other people can follow the same work and get similar results. A laboratory notebook is useful in school labs, research settings, and industry. It can also become a legal record when an idea, process, substance, or technique is patented and...

basic organic chemistry techniques

Organic Lab Glassware and Safe Handling

Organic chemistry labs use specific glassware, careful weighing steps, and controlled heating to keep reactions safe and accurate. Beakers and Erlenmeyer flasks are often used for mixing or holding solvents, but they are not meant for measuring volume unless only an approximate amount is needed. Volumetric glassware is used when a precise volume matters. This group includes graduated cylinders, volumetric pipettes, and volumetric flasks. A graduated cylinder is commonly used in the organic lab...

melting points

How Impurities Change Melting Points

Melting point helps identify an organic compound by showing the temperature where a solid turns into a liquid at 1 atmosphere of pressure. It is a physical property, like solubility, density, color, and electronegativity. Because the exact start of melting is hard to measure, the result is reported as a range. The lower end is when the first drops of liquid appear. The upper end is when the last solid has melted. Scientists compare this range with literature values to help identify a compound. <br...

boiling points

Boiling point and vapor pressure are key physical properties of a liquid. For a pure compound, the boiling point can help identify the substance. In experiments, the boiling point is usually recorded as a range because exact values are hard to measure and may differ by a few degrees from the literature value. Vapor pressure explains why a liquid boils. In a sealed container, some molecules at the liquid surface gain enough energy to escape into the gas phase. At the same time, some gas...

recrystallization

Purifying Crystals by Solubility

Purifying crystals by solubility is a key organic chemistry technique. Recrystallization uses differences in solubility to separate a desired solid product from starting materials, solvent, and impurities. It is one of the three standard purification methods, along with distillation and extraction. Solubility is the maximum amount of a substance that can dissolve in a fixed volume of solvent at a given temperature. Different solutes dissolve in different solvents, and their behavior can vary...

extraction

Separating Mixtures with Solvent Extraction

Solvent extraction is a common way to separate and isolate a target compound in organic chemistry. In this process, a solute moves from one phase to another so it can be separated from unreacted starting materials or impurities. Extraction is also useful when a product is dissolved in a reaction solvent that is hard to remove by evaporation, such as a solvent with a high boiling point. There are three main types of extraction. In solid-liquid extraction, the solute moves from a solid phase...

simple distillation

Separating Liquids by Boiling Point

Separating liquids by boiling point is the goal of distillation. A miscible mixture contains liquids that mix evenly, and it can be heated so that the more volatile liquid evaporates first. Volatility is a liquid’s tendency to vaporize, and boiling begins when bubbles form in the liquid phase. In a closed container, liquid and vapor can reach equilibrium, which means the rate of vaporization equals the rate of condensation. The pressure from the vapor above the liquid is called vapor pressure.

steam distillation

Steam Distillation and Low-Boiling Separation

Steam distillation is a separation method for temperature-sensitive organic compounds. It works best when the organic compound is immiscible in water, meaning the two liquids do not mix. The method helps remove the organic molecule from a non-volatile contaminant without using the higher temperatures needed for many other separations. In steam distillation, the immiscible mixture is heated until both water and the volatile organic compound distill together. The vapor rises to a condenser,...

thin-layer chromatography

TLC Separation by Polarity

Thin-layer chromatography (TLC) separates compounds in a mixture by polarity. It uses the same basic parts as other chromatography methods: a stationary phase, a mobile phase, and the solute. In TLC, the stationary phase is a thin coating on a plate instead of material packed into a column. The stationary phase in most TLC systems is polar silica gel, a form of silicon dioxide. Its surface has OH groups that can form hydrogen bonds. The sample is first spotted on a pencil start line with a...

column chromatography

Separating Mixtures by Polarity

Column chromatography separates compounds in an organic chemistry lab by using differences in physical properties. It is especially useful for microscale separations when less than 10 grams of material is available for analysis. The method can separate a mixture based on solubility, polarity, hydrophobicity, size, and charge. Any chromatography system has three main parts: the stationary phase, the mobile phase, and the sample mixture. In column chromatography, the stationary phase is usually...

hydrolysis of an ester

Soap Formation from Triglycerides

Triglycerides are lipids made of a glycerol backbone linked to three fatty acids. They are common in vegetable oils and animal fats. Plant lipids are the basis of vegetable oils, while animal lipids are used as lard or general sources of fats. A fatty acid has a long carbon chain, usually between 12 and 20 carbons, with a weak organic acid at one end. Some fatty acids contain double bonds. These are unsaturated fats. The double bond usually gives the chain a bent, cis shape. As a result,...

synthesis of luminol

Luminol Chemiluminescence in Forensics

Luminol chemiluminescence shows how a chemical reaction can produce light and help with blood detection. Chemical reactions may be endothermic or exothermic, depending on whether they absorb or release heat as reactants become products. The enthalpy of a reaction is the energy difference between reactants and products, or ΔH. A positive ΔH means the reaction is endothermic. A negative ΔH means it is exothermic. Many reactions do not happen in a single step. They can pass through intermediates...

esterification

Ester Formation and Everyday Fragrances

Esters are organic compounds with a carbonyl group attached to an oxygen that connects to another alkyl or aryl group. Their general formula is RCOOR'. They are often made by reacting a carboxylic acid with an alcohol in an esterification reaction. In this process, the hydroxyl group of the acid is replaced by an alkyl or aryl group. Many simple esters have familiar fruit and flower smells because their structures are small and less complex. Formic acid and methanol can combine to form methyl...

identification of unknown aldehydes and ketones

identification-of-unknown-aldehydes-and-ketones

Carbonyl Tests for Aldehydes and Ketones

Aldehydes and ketones are carbonyl compounds, which means they contain a C=O functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon. Acetone is the simplest ketone, with two methyl groups. An aldehyde is similar, but it has at least one hydrogen attached to the carbonyl carbon. Formaldehyde is the simplest aldehyde, and acetaldehyde has one hydrogen and one methyl group. The carbonyl carbon in both aldehydes and ketones is electrophilic because the oxygen atom...

uv-vis spectroscopy of dyes

How Dyes Absorb Visible Light

Dyes absorb visible light because their molecular structure lets them interact with specific wavelengths. When light hits a substance, some light is absorbed and the rest is reflected or transmitted. The color we see depends on the wavelength that is reflected. A blue substance reflects blue light, around 430 to 480 nm, and absorbs the complementary orange region, around 590 to 630 nm. Compounds that do not absorb in the visible range appear colorless to the human eye. Light also has energy and...

identifying alcohols

Alcohol Tests for Primary, Secondary, and Tertiary

Alcohol tests can help sort alcohols by structure and reactivity. Alcohols are organic molecules with a hydroxyl group attached to an alkyl or aryl group, written as ROH. If the carbon with the hydroxyl group has one R group, the alcohol is primary. If it has two R groups, it is secondary. If it has three R groups, it is tertiary. Alcohols can also be aromatic when they contain a benzene ring. Phenol is the simplest aromatic alcohol. To identify an alcohol, chemists can use its chemical...

chemistry

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Explore how vapor pressure, volatility, and intermolecular forces affect boiling point, and learn how the capillary method measures it in the lab.

Boiling Point and Vapor Pressure | JoVE K12

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Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Chemical Bonds

Boiling Point Determination
Similar to the melting point, the boiling point is a physical property. If the sample is a pure compound, then the boiling ...

Melting Points

Melting Points in Organic Chemistry
The melting point of a compound is the temperature at which the solid phase transitions into the liquid phase at a ...

Melting Point

Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA
One of the most important properties of a crystalline ...

Electrolyte and Nonelectrolyte Solutions

Substances that undergo either a physical or a chemical change in solution to yield ions that can conduct electricity are called electrolytes. If a ...

ionic-compounds-formulas-and-nomenclature

Ionic Compounds: Formulas and Nomenclature

An element composed of atoms that readily lose electrons (a metal) can react with an element composed of atoms that readily gain electrons (a nonmetal) to ...

molecular-compounds-formulas-and-nomenclature

Molecular Compounds: Formulas and Nomenclature

Molecular compounds or covalent compounds result when atoms share electrons to form covalent bonds. Since there is no electron transfer, molecular ...

Chemical Symbols

A chemical symbol is an abbreviation that is used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. We use the ...

Chemical Formulas

A chemical formula presents information about the proportions of atoms constituting a particular chemical compound or molecule, mainly using symbols of ...

Chemical Names and Chemical Formulas

Obtain, evaluate, and communicate information to explain how atoms bond to form stable compounds.

Boiling Point and Vapor Pressure

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