As the title says I am searching for an example for such a molecule, because we need to make one in our summary (about Van-der-Waals forces) we need to hand in tomorrow.
I'm currently working on a lesson for a micro-teach that asks students to investigate how geckos stick to almost all surfaces. For this assignment, I have to make some activities that provide "puzzle pieces" for students to start putting together the full explanation of the phenomenon so that they can create a model of what's happening. I have an idea for surface area -- asking students to compare how much contact different materials (e.g., bubble wrap and a soft-bristle brush (meant to represent the setae on gecko feet)) make with the carton -- but I am very stuck on ways to represent van der Waals forces. I will be giving them a definition of what VDW forces are, but I need something for them to work through to help solidify the concept. I was thinking of doing something with tape or Velcro to show the cumulative effects of weak forces, but I'm not sure how to make that into a full activity. Any feedback or suggestions?
Side note: I'm not actually teaching this lesson to high schoolers -- this is for a grad school class, so I will be presenting to my classmates. I only have 20 minutes to do these activities for the class.
I'm hoping someone can help. I was reading about gauge blocks yesterday and I’m a complete novice in this area so please correct me if I’m wrong. This topic is absolutely fascinating.
https://en.wikipedia.org/wiki/Gauge_block#cite_note-NIST2-5
Basically, gauge blocks which are hard and ultraflat have an attractive, binding property which can join together with considerable force. The blocks can be metallic or non-metallic, like ceramic, so the force isn’t magnetic. The blocks need to be joined in a sliding process called “wringing”, in order to squeeze the air out between the two pieces; just banging the two pieces together won’t work. Gauge blocks also need a tiny film of oil to help with surface tension. Gauge blocks can work in a vacuum, so air pressure isn’t considered to be a major but is a contributory factor? Most sources online agree the force is intermolecular, but don’t specify which force exactly. Examples of Intermolecular forces can include Van der Waals force, London Dispersion force and hydrogen bond forces.
Van der Waals forces are extremely short range. https://en.wikipedia.org/wiki/Optical_contact_bonding
However this link says: “Intermolecular forces such as Van der Waals forces, hydrogen bonds, and dipole-dipole interactions are typically not sufficiently strong to hold two apparently conformal rigid bodies together, since the forces drop off rapidly with distance, and the actual area in contact between the two bodies is small due to surface roughness and minor imperfections. However, if the bodies are conformal to an accuracy of better than 10 angstroms (1 nanometer), then a sufficient surface area is in close enough contact for the intermolecular interactions to have an observable real world physical manifestation—that is, the two objects stick together. Such a condition requires a high degree of accuracy and surface smoothness.”
As an interesting side note: It's accepted that Van der Waals forces explain how geckos walk up walls. They splay out long hairs on their toes which increases surface area in order to stick to the wall. When they
... keep reading on reddit ➡They seem to play similar roles in many situations. I’m not entirely sure how they differ from one another.
We recently did an experiment lowering paper clips into water without making it sink, but our teacher never really explained what it was, just that it made stuff float. Now, we have a question where we have to explain how three hydrogen bonded water molecules supports he special ability of a water strider
I have an exam in a few weeks and seem to be getting conflicting information from different sources on this question.
Like I don't get how something so supposedly weak can end up being used by nature to build so many things including stuff like membranes for the cells which basically make up our entire body.
I mean is it just induced dipole dipole interactions or is there something more?
Hello, Reddit chemists!
I'm a Respiratory Therapy student, and we're going over some refreshers right now in terms of chemistry and physics. One thing that bothers me is they describe in my textbook that solids retain their shape due to strong mutual forces called van der Waals forces. I don't know if I'm understanding this incorrectly, but I remember back from college times that van der Waals were the weakest of all forces, and they're really just existing pretty much everywhere, including in gases. I remember primarily covalent and ionic bonds being responsible for keeping the shape. Is there an exception to this rule? I know there are different types of van der Waals forces, but is this what truly helps solids maintain their shape?
Thank you!
First off, what are van der Waals forces? They seem to include London dispersion and sometimes dipole-dipole (though the book I'm reading lists dipole-dipole separately). I always see vdw defined differently and it seems like a very general umbrella term.
Secondly, the book I'm reading lists London forces as between the hydrophobic regions of molecules. This doesn't seem quite right to me. I've always known London forces to be present between all molecules, so what about a small polar molecule like H2O? That doesn't seem to fit the books description, but it should still have London forces.
I’ve been reading some stuff about it but the definitions are so convoluted and not in lay men’s terms. I can’t understand what it is.
I think all the forces mentioned in the title are the same but my book had this weird idea of 'instantaneous dipole-instantaneous dipole forces' which I don't get at all.
I don't think those forces exist, I think there's only 'instantaneous dipole-induced dipole forces'.
I also think that 'instantaneous dipole-instantaneous dipole forces', 'london forces', 'van der waals forces' and 'london dispersion forces' are more or less the same exact thing.
Here's the page in my book talking about all of this: https://imgur.com/a/nFv2Tib
Edit: Could 'instantaneous dipole-instantaneous dipole forces'/'london dispersion forces' be in-between molecules (Cl2-Cl2) and 'instantaneous dipole-induced dipole forces'/'london forces'/'van der waals forces' be in-between the two atoms in a molecule (Cl-Cl)?
For example, can every Hydrogen bond be explained with Van der Waals, or are they different?
