Description
This demonstration explores the phenomenon of lost volume. Fifty milliliters each of ethanol and water are simultaneously poured into a 100-mL volumetric flask. To students’ surprise, the combined liquid volume is less than 100 mL. Bubbles and an increase in temperature are noted as the mixed solution sits in the flask. Students apply their prior knowledge of chemical and physical properties to develop a model for what happens at a molecular level.
Time Requirement
Total, 15 minutes. Teacher prep, 5 minutes. Demonstration and discussion, 10 minutes.
Digital Resources
Includes 1-year access to digital resources that support 3-dimensional instruction for NGSS. Digital resources may include a teacher manual and student guide, pre-lab activities and setup videos, phenomenon videos, simulations, and post-lab analysis and assessments.
Crosscutting Concepts
Structure and Function
Patterns
Science and Engineering Practices
Planning and Carrying Out Investigations
Learning Objectives
- Apply prior knowledge to predict the total volume of a mixture containing equal parts ethanol and water.
- Illustrate and explain the intermolecular forces between water and ethanol.
- Learn how to use volumetric glassware.
Prerequisite Knowledge and Skills
Students should be familiar with intramolecular forces versus intermolecular forces, hydrogen bonding between molecules, polar versus nonpolar molecules, and the law of conservation of mass.