11: Evaporation and Intermolecular Attractions
- Page ID
- 514173
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- To investigate the relationship between intermolecular forces and the evaporation rate by measuring temperature changes.
- To compare the strength of dispersion forces and hydrogen bonding in alkanes and alcohols based on their molecular structure and evaporation behavior.
- To predict and analyze the temperature change (∆T) of different substances based on their intermolecular forces and molecular weight.
INTRODUCTION
Evaporation is a phase change in which molecules transition from the liquid state to the gaseous state. This process is endothermic, meaning it requires energy in the form of heat from the surrounding environment. As a result, the temperature of the remaining liquid and the surrounding surface decreases. The extent of this temperature drop depends on the strength of intermolecular forces present in the liquid.
Intermolecular forces dictate many physical properties of substances, including viscosity, boiling point, and evaporation rate. The three main intermolecular forces are London dispersion forces, dipole-dipole interactions, and hydrogen bonding. London dispersion forces are present in all molecules and become stronger as molecular weight increases. Dipole-dipole interactions occur between molecules with permanent dipoles. In contrast, hydrogen bonding—a powerful form of dipole interaction—occurs in molecules containing hydrogen directly bonded to nitrogen (N), oxygen (O), or fluorine (F).
In this experiment, temperature probes will be used to measure the temperature change caused by the evaporation of different organic liquids, including alkanes and alcohols. Alkanes, which consist only of carbon and hydrogen, exhibit only dispersion forces, while alcohols, which contain an –OH (hydroxyl) functional group, experience both dispersion forces and hydrogen bonding. By comparing the temperature changes of these substances during evaporation, the strength of their intermolecular forces can be assessed. Additionally, the molecular structure, molecular weight, and hydrogen bonding capability of each liquid will be analyzed to predict and interpret the experimental results.
- 11.1: Evaporation and Intermolecular Attractions - Experiment
- This page details safety precautions for handling volatile and flammable liquids, emphasizing ventilation and protective gear. It lists the necessary equipment and chemicals for an experiment measuring temperature changes in various alcohols and alkanes, including ethanol and n-hexane, while predicting outcomes based on molecular properties. Additionally, it outlines proper disposal methods for used materials and chemicals.
- 11.2: Evaporation and Intermolecular Attractions - Pre-lab
- This page presents a pre-lab activity for students to analyze organic compounds, specifically focusing on their structural formulas, molecular weights, and hydrogen bonding capabilities. The compounds for analysis include ethanol, 1-propanol, 1-butanol, n-pentane, methanol, and n-hexane. The exercise is designed to enhance students' understanding of the chemical properties and interactions of the substances studied.
- 11.3: Evaporation and Intermolecular Attractions - Data and Report
- This page presents a data table to observe temperature changes (\(T_{\max}\), \(T_{\min}\), \(\Delta T\)) in various substances, focusing on alcohols and hydrocarbons. It encourages students to analyze how intermolecular forces influence temperature changes, despite similar molecular weights.