Van Der Waals Bonding Puns

And if we don't have why?

Hello,

My friends and I were debating this the other day. For me, there is no way that scissors could break the carbon carbon bonds. I think it is more likely that the pressure of the scissors is enough to pull the molecules appart

Can someone help us on this matter? I couldn't fine anything on the internet.

Meh, should have read the title before posting. Sorry about that

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.

What type of chemical bond is breaking when C10H8 sublimated? I answered none is breaking, but van der Waals is gained when it becomes solid. C10H8 (g) + energy -> C10H8 (s)

Why was this incorrect?

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

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.

They seem to play similar roles in many situations. I’m not entirely sure how they differ from one another.

He generally preferred weak interactions.

I was wondering the status of non-local van der Waals like DF2 in CASTEP. Thanks!

Ron Cohen

I'm hoping you all could help me understand what exactly this question is asking. I've been staring at it for a while now wondering if it could be as simple as I'm starting to think it is.

So as the title says, we have two xenon atoms that are bonded at zero temperature. It gives ϵ=20meV and σ=3.94Å

It asks for the interatomic separation, and the amount of energy needed to break the bond.

Here is my thought process thus far:

At zero temperature, there is no potential energy. Is this correct? And at zero temperature, xenon forms a FCC structure.

Since we're dealing with van der Waals bonds, we look to the Lennard-Jones potential:

U(r)=4ϵ[(σ/r)^(12)-(σ/r)^6]

So since the temperature is zero, according to the IAE curve, the interatomic separation occurs at r=σ where U(r)=0. Is this correct?

Now in my notes, we have the Lennard-Jones potential set up for an FCC crystal:

U_tot=2Nϵ[12.131(σ/r)^(12)-14.454(σ/r)^6]

So in this case, r is the interatomic separation. Correct? So now we take the derivative and set it equal to 0, then solve for r. This gives us:

r=1.089σ

Do I literally just plug in the given σ=3.94Å and that's my answer?

and as for the energy needed to break the bond, this is just -ϵ at r_min on the IAE curve. Correct? So is my answer just -20meV from the given ϵ?

Thanks so much for your help

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