Materials Science C

[bhavjain]

Short Event Description: Teams will answer a series of questions or complete tasks involving the science processes of chemistry focused in the areas of materials science.

What is Young's modulus a measure of, and what is its formula?

[slowpoke]

what is matsci (Click to Show Hidden Text)

"stiffness" of a material, stress/strain

[bhavjain]

what is matsci (Click to Show Hidden Text)

"stiffness" of a material, stress/strain

Correct! Stess/strain can also be represented as . Your turn.

[d4dd7y00n]

Short Event Description: Teams will answer a series of questions or complete tasks involving the science processes of chemistry focused in the areas of materials science.

What is Young's modulus a measure of, and what is its formula?

Young's modulus measures the elasticity of an object. The formula for Young's Modulus is stress/strain, or F/A/(delta(L)/L). A stands for the cross sectional of the object, and F is forced applied. L stands for the original length of an object, and delta L stands for change in length of the object.

[hearthstone224]

Can someone ask a new question, or should I ask a new one? I'll just ask one anyways.

What are Van der Waals Forces and what do they have to do with Materials Science?

[hearthstone224]

Eh, here's another good one. What kind of forces hold together Liquid Hydrogen?

[Avogadro]

Interesting... (Click to Show Hidden Text)

London Dispersion Forces?

[hearthstone224]

The answer was Van der Waals which London Dispersion is a part of, so correct!

Can you explain why though? I was actually asking this for my own benefit too. I wasn't sure why the answer was LDF and so I wanted to know why.

[Avogadro]

In case someone wants to guess (Click to Show Hidden Text)

The way I tend to handle these problems is basically process of elimination. All things experience LDFs (/van der Waals) because all things have electrons that can move around to create partial charges and attraction. Though they say that it is liquid hydrogen and the word hydrogen will often take your mind to hydrogen bonds, because the structure of the molecules within liquid hydrogen is H---H, there is no N, O, or F to create an actual hydrogen bond (if that explanation made any sense). Additionally, because H and... H... have the same electronegativity, there is no dipole, so all dipole-related interactions are ruled out. Therefore the only remaining plausible forces are LDFs/van der Waals forces.

And a question: Explain why CH4 is a gas at room temperature but C10H22 is a liquid.

[hearthstone224]

In case someone wants to guess (Click to Show Hidden Text)

The way I tend to handle these problems is basically process of elimination. All things experience LDFs (/van der Waals) because all things have electrons that can move around to create partial charges and attraction. Though they say that it is liquid hydrogen and the word hydrogen will often take your mind to hydrogen bonds, because the structure of the molecules within liquid hydrogen is H---H, there is no N, O, or F to create an actual hydrogen bond (if that explanation made any sense). Additionally, because H and... H... have the same electronegativity, there is no dipole, so all dipole-related interactions are ruled out. Therefore the only remaining plausible forces are LDFs/van der Waals forces.

And a question: Explain why CH4 is a gas at room temperature but C10H22 is a liquid.

Avogadro if I'm not mistaken, LDF's rely upon dipoles to form, right? Isn't LDFs between two induced dipoles for example maybe water molecules where electrons are shifted? I actually looked back and I realize that maybe the dipole-dipole could happen too since the dipoles are still there.

Either way, the answer would be van der waals forces (since all these interactions are counted as van der waals interactions.)

Anyways, I will try to answer your question.

I looked online and this is my answer. Liquids become gases when the kinetic energy overcomes the attractive forces. CH4 has low attractive forces because it is first off tetrahedral, and because the bond is nonpolar covalent, meaning the electrons are shared evenly, there are no dipoles therefore cancelling out a lot of IMFs. Since it has very low attractive forces, it becomes a gas very easily.

On the other hand, C10H22 (decane) is a liquid because I'm assuming it has a lot more IMFs. It is a large chain structure and there is bound to be a lot of dipole interactions and London Dispersion forces going on.