# Tutor profile: Steven C.

## Questions

### Subject: Chemistry

What is sp3 hybridization and in which elements does it often occur?

Hybridization is the process of which orbitals of different characteristic energy levels combine to create a lower energy state within the atom. Specifically, sp3 hybridization is the hybridization of an s-orbital and the three p-orbitals in the outer-most shell of the atom. The new sp3 orbital creates four orbitals, usually each containing one unpaired electron. This type of hybridization is often found in group 14 elements such as Si and Ge.

### Subject: Calculus

How does one find the x-intercept, or the zero, of the second derivative of a given plotted function?

The second derivative of a given function will equal zero at the point of inflection of the original function. The inflection point is the point at which the curvature of the function changes from an increasing slope to a decreasing slope. In the plot of the first derivative, this point will be represented by either a maximum or minimum.

### Subject: Materials Science

How does the molecular weight of a polymer affect it's measured viscosity?

Polymers have a characteristic critical molecular weight of entanglement, which is a known value for a specific polymer. Above this critical molecular weight, individual polymer chains entangle with one another, which changes how viscosity of the polymeric melt is affected. Above this critical molecular weight, the logarithm of viscosity increases with increasing molecular weight by a factor of 3.4, while below the critical molecular weight, the logarithm of viscosity increases by a factor of 1.0.

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