EIT Chemistry and Materials Science 2

Question 1

Which type of bond results from the sharing of electrons between two atoms?

Accepted Answer

Covalent bond

Answer

Covalent bonds form when atoms share electron pairs, as in H₂, H₂O, and organic molecules.

Question 2

The yield strength of a material is defined as the stress at which:

Accepted Answer

Significant permanent (plastic) deformation begins

Answer

Yield strength marks the onset of plastic deformation — below this stress, deformation is elastic and recoverable.

Question 3

In an iron-carbon phase diagram, the eutectoid composition occurs at approximately:

Accepted Answer

0.76 wt% C at 727°C

Answer

The eutectoid point in the Fe-C system is 0.76 wt% C at 727°C, where austenite transforms to pearlite (ferrite + cementite).

Question 4

The rate of a chemical reaction generally __________ with increasing temperature.

Accepted Answer

Increases exponentially (Arrhenius)

Answer

Arrhenius equation k = Ae^(−Ea/RT) shows exponential increase in rate constant k with temperature T.

Question 5

Polymer glass transition temperature (Tg) is the temperature below which the polymer becomes:

Accepted Answer

Rigid and glassy (brittle)

Answer

Below Tg, chain mobility freezes and the polymer becomes stiff and brittle like glass; above Tg it is rubbery.

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