Unit 11: Solids and Liquids: The condensed states of matter
Reading
BJU Chemistry: Ch. 11 "Solids and Liquids"
Zumdahl Chemistry: Ch. 10 "Liquids and Solids"
Topics
Labs
Boron Compounds lab, with flame testing of several metal-chlorides to observe emission spectra.
BJU Chemistry: Ch. 11 "Solids and Liquids"
Zumdahl Chemistry: Ch. 10 "Liquids and Solids"
Topics
- Hydrogen bonds
- Dipole-dipole forces
- Dispersion forces
- Properties of solids and liquids
Labs
Boron Compounds lab, with flame testing of several metal-chlorides to observe emission spectra.
Below: Solids and liquids are held together by INTERmolecular forces. The atoms in a solid vibrate in place, while the atoms in a liquid can slide past one another. You can't see or feel the atoms vibrate; they're way too small for that.
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LIQUID STATE
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Below: The four states of matter. As you add heat to a solid, the atoms increasingly vibrate and start sliding past one another, at which point you have a liquid. As even more heat is added, the atoms begin to leave entirely and take on the gaseous phase. Under intense heat, even the subatomic particles break apart and you have a plasma.
Lecture overview
Up to this point we have been discussing INTRAmolecular forces, the forces which BOND ATOMS together. These fall into three broad categories: 1) Ionic bonds, 2) Covalent bonds, and 3) Polar-covalent bonds. We also discussed Metallic bonds, as well.
Now we are switching gears and talking about INTERmolecular forces, the forces which hold molecules together to form LIQUIDS and SOLIDS.
These INTERmolecular forces come in three types:
All three of these intermolecular forces are termed "Van der Waal" forces. Be aware that some books only refer to London Forces as Van der Waal forces. This can sometimes be a source of confusion, so now you have been warned.
INTERmolecular forces are WEAK forces: A hydrogen bond represents only about 20 KJ/mol, and Dispersion forces only represent <5 KJ/mol in strength - whereas a typical Covalent bond is around 400-500 KJ/mol. Think about it though: if intermolecular forces were much stronger we wouldn't have any liquids or gases in nature; everything would just be a SOLID! So there's a lot of careful "design" apparent here, as in many other places.
Up to this point we have been discussing INTRAmolecular forces, the forces which BOND ATOMS together. These fall into three broad categories: 1) Ionic bonds, 2) Covalent bonds, and 3) Polar-covalent bonds. We also discussed Metallic bonds, as well.
Now we are switching gears and talking about INTERmolecular forces, the forces which hold molecules together to form LIQUIDS and SOLIDS.
These INTERmolecular forces come in three types:
- Dipole-dipole forces, the electrostatic attraction between the (+) and (-) ends of polar molecules
- Hydrogen bonds, the electrostatic attraction between a Hydrogen on one compound, and either Oxygen, Nitrogen, or Fluorine on an adjacent compound
- Dispersion forces (London forces), the fairly-weak electrostatic attraction between non-polar molecules which arises from an unequal distribution of their respective electron-clouds at any given instant.
All three of these intermolecular forces are termed "Van der Waal" forces. Be aware that some books only refer to London Forces as Van der Waal forces. This can sometimes be a source of confusion, so now you have been warned.
INTERmolecular forces are WEAK forces: A hydrogen bond represents only about 20 KJ/mol, and Dispersion forces only represent <5 KJ/mol in strength - whereas a typical Covalent bond is around 400-500 KJ/mol. Think about it though: if intermolecular forces were much stronger we wouldn't have any liquids or gases in nature; everything would just be a SOLID! So there's a lot of careful "design" apparent here, as in many other places.
| Handout: Chemical Bonding Chart |
2020 class: Boron Compounds Lab
- Synthesize some really cool compounds based on the element 'Boron'
- Carry out flame tests on various metals to observe emission spectra. Talk about what that means...
| boron_compounds_lab_handout.pdf |
| flame_test_chart_metal_ions.png |
Homework
| 10._solids___liquids_homework__2023.docx |
| 10._know_your_ions_part_2..docx |