Boiling point and forces
About this app
Rank series by boiling point, heat them and pull one molecule out of the liquid: light bands tear, and nothing tears inside the molecule. Alkanes, alcohols, isomers and hydrogen halides with measured values, two substances in the same heating bath, a lens in the gas and solubility in water and hexane.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
What it is about
During boiling, molecules separate from each other. The heat overcomes the forces between the molecules, and the covalent bonds inside them stay whole. Van der Waals forces act between all molecules and grow with contact area and electron number. Dipole-dipole interactions need polar molecules, and hydrogen bonds need H on O, N or F. Evaporating ethanol costs about 39 kJ/mol, while splitting one C–C bond costs about 347 kJ/mol.
What the app shows
Molecules lie in a vessel, and light bands show the kind of forces between them. The thermometer stands still during boiling while the heat separates molecules. If you pull one molecule out, the light bands tear, and nothing tears inside the molecule. The boiling points are measured values at 1013 hPa for alkanes, alcohols, isomers, hydrogen halides and substances of similar mass. The simulation itself is qualitative: the molecules are rigid and the gas space is greatly reduced.
What you try out
You rank a series by your prediction, heat the substances and compare with the measurement. In the gas you use the lens to check that whole molecules fly. In the comparison two substances stand in the same heating bath, such as ethanol and methoxymethane or HF and HBr. Finally you add alcohols from methanol to hexan-1-ol, and hexane, to water and hexane and see where they go. Eight test questions with reasons secure the result.
Frequently asked questions
- Do covalent bonds break when a liquid boils?
- No. Boiling overcomes only the forces between the molecules. The molecules stay whole, and on cooling the same substance condenses. Evaporating ethanol costs about 39 kJ/mol, splitting a single C–C bond about 347 kJ/mol.
- Why does ethanol boil so much higher than methoxymethane?
- Both have the formula C₂H₆O. Only ethanol has an H atom on the oxygen and forms hydrogen bonds. Ethanol boils at 78.3 °C, methoxymethane at −24.9 °C, about 103 K lower.
- Why do branched alkanes boil lower than straight ones?
- Isomers have the same mass and electron number. A strongly branched molecule is more spherical and touches its neighbours over a smaller area, so the van der Waals forces are weaker. Pentane boils at 36.1 °C, 2,2-dimethylpropane at 9.5 °C.
- What can I do in the app myself?
- You predict rankings, heat substances, pull a molecule out of the liquid and test solubility. An explain mode uses ethanol to guide you through boiling.
Subject: Chemistry
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