Evaporation of Alcohols

Contributor
Vernier Software & Technology
Type Category
Instructional Materials
Types
Experiment/Lab Activity
Note
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.

Reviews

Description

In this lab activity, students use a digital temperature probe to compare the temperature changes when four different alcohols evaporate. The analysis questions provided guide students to connecting the energy changes associated with the change of state with the structure of molecules of substances. Before beginning the lab, students are asked to consider the structural formulas of the alcohols used in the lab: methanol, ethanol, 1-propanol, and 1-butanol. After collecting data for the first three alcohols, students predict the temperature change for 1-butanol and then collect data to test their prediction. The resource linked here is a sample. More complete information, including teacher’s guide and safety information, is available for purchase from Vernier Software and Technology using the link provided on the final page of the sample.

Intended Audience

Learner
Educational Level
  • Grade 12
  • Grade 11
  • Grade 10
  • Grade 9
  • High School
Language
English
Access Restrictions

Limited free access - Some material is available for viewing and/or downloading but most material tends to be accessible through other means.

Performance Expectations

HS-PS1-3 Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.

Clarification Statement: Emphasis is on understanding the strengths of forces between particles, not on naming specific intermolecular forces (such as dipole-dipole). Examples of particles could include ions, atoms, molecules, and networked materials (such as graphite). Examples of bulk properties of substances could include the melting point and boiling point, vapor pressure, and surface tension.

Assessment Boundary: Assessment does not include Raoult’s law calculations of vapor pressure.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
The brief introductory paragraph to this activity provides information for students to connect the strength of attraction between the molecules of a liquid to the rate of evaporation of the substance. It is up to the student to make sense of these statements through analysis of the pattern exhibited in the data and connecting the pattern to the molecular structures in connection to the intermolecular forces. To better address this PE, students could use the information from this introductory paragraph to choose substances to study in this lab. Alternatively, after this activity, students could choose another small set of substances to collect data for to compare to the alcohols previously examined to further test the claims they developed from the alcohol data.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students are expected to use their structural formula drawings of the molecules with the data collected to construct claims about the attraction between the molecules in the alcohols examined. The practice would be easily implemented in a classroom that is employing the Claim-Evidence-Reasoning (CER) framework for constructing explanations. For additional information on the CER Framework see the NSTA Web Seminar “How Do You Know That? Helping Students Write About Claims and Evidence” presented by Dr. Jodi Wheeler-Toppen. In this program Dr. Wheeler-Toppen shared strategies for using claims, evidence, and reasoning in the classroom. http://learningcenter.nsta.org/products/symposia_seminars/NSTA/webseminar16.aspx

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
The analysis questions provided for the lab in the section titled Processing the Data, focuses students on the key concept of how the forces between molecules in a substance affect the properties of the substance. In particular, the third question: “Which of the alcohols studied has the strongest attractions between its molecules? The weakest attractions? Explain, using the results of this experiment.” draws students attention to this concept. These questions should be used to ensure students have taken the opportunity to consider connections between the observed data and the electrical forces between the molecules based on their structures. The analysis questions provide a clear connection of considering the forces between molecules as a means to explain the pattern of the data observed in the lab. The activity does not, however, provide the means for students to understand why the larger chain in 1-butanol would yield a greater change in temperature during evaporation and a higher boiling temperature. In order to fully understand this DCI, students will need further study on the relationship between the structure of matter and the interactions between the particles (i.e. intra- and intermolecular forces).

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
The connection between structure of molecules and their properties in this lab is related to the length of the carbon chain (or molecular weight) in this activity. To support students in a deepen understanding of the connection between the structures of molecules and their properties, they must have additional opportunities to explore this idea with further examples beyond this set of four alcohols and the particular pattern exemplified with this activity.

Resource Quality

  • Alignment to the Dimensions of the NGSS: The lesson activities provide appropriate opportunities for students to work together in three-dimensional learning to make sense of data collected in a lab experience. The only connection to natural phenomenon is made in the introductory paragraph for the activity. In the introduction there is a brief statement connecting the evaporation process to the feeling of stepping out of a swimming pool on a windy day. Students are not expected to connect the lab results to this phenomenon.

  • Instructional Supports: The questions in the lab activity provide opportunities for students to connect observations from the activity to molecular-level representations of the alcohols. As previously noted, there is a brief connection to the natural world in the introduction to the activity that can provide an opportunity for students to connect the learning to their own experiences, but this connection is underemphasized in the student questions.

  • Monitoring Student Progress: Monitoring student progress is left to the teacher’s discretion. There are opportunities in the lab procedure following the collection of data for the first three alcohols that a teacher can use as probing questions for formative assessment with small lab groups or facilitating whole class discussions.

  • Quality of Technological Interactivity: This review pertains to the written lab activity and not the technology aspects of data collection and analysis during the activity.