## Materials Science C

bhavjain
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### Materials Science C

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?
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slowpoke
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### Re: Materials Science C

"stiffness" of a material, stress/strain
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William P. Clements HS '17

bhavjain
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### Re: Materials Science C

slowpoke wrote:
"stiffness" of a material, stress/strain
Correct! Stess/strain can also be represented as $E = \frac{FL_0}{A_0\Delta L}$. Your turn.
2017 Science Olympiad - (Invites TBD/Reg/State/Nats) - Division C

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d4dd7y00n
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### Re: Materials Science C

bhavjain wrote: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
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### Re: Materials Science C

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?
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hearthstone224
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### Re: Materials Science C

Eh, here's another good one. What kind of forces hold together Liquid Hydrogen?
End of freshman season. Good luck to everyone! No state for us, but nevertheless great season. Regional was out of 12 teams. (CLC)

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### Re: Materials Science C

London Dispersion Forces?
Lower Merion 2017
Subtitled: Revenge of the Non-Harriton

Placement Record:

Code: Islip | Conestoga | Tiger | Regionals | States
Out of: 61 | 42 | 36 | 37 | 36

Chemistry Lab: 9 | - | - | 4 | 4
Astronomy: 14 | - | 5 | 10 | 3
Material Science: 12 | 19 | 9 | 5 | 9
Optics: 14 | 7 | 3 | 4 | 2

hearthstone224
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### Re: Materials Science C

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.
End of freshman season. Good luck to everyone! No state for us, but nevertheless great season. Regional was out of 12 teams. (CLC)

Mat Sci-> Second at regionals
RSensing -> First at regionals
Towers-> Third at regionals.

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### Re: Materials Science C

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.
Lower Merion 2017
Subtitled: Revenge of the Non-Harriton

Placement Record:

Code: Islip | Conestoga | Tiger | Regionals | States
Out of: 61 | 42 | 36 | 37 | 36

Chemistry Lab: 9 | - | - | 4 | 4
Astronomy: 14 | - | 5 | 10 | 3
Material Science: 12 | 19 | 9 | 5 | 9
Optics: 14 | 7 | 3 | 4 | 2

hearthstone224
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### Re: Materials Science C

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.)