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    Comparison of Chemicals/Compound Properties

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    I need some help in questions pertaining to the comparison of chemicals and compound properties:
    1. Explain in terms of viscosity and intermolecular bonding why (10-30) weight motor oil protects your car's engine better in the winter time and (20-40) better in the summer time.

    2. Explain why in terms of surface tension, why water beads up on a cold day on a freshly waxes car hood and forms nearly spherical drops (in outer space they are perfect spheres). Also, why have water bugs almost become extinct due to high detergent use since the 50's.

    3. Explain in terms of heat vaporization why you feel cool when you get out of the pool in Las Vegas on a breezy 110 Fahrenheit summer day.

    4. Explain why ice is less dense than water, and therefore floats on water. (A diagram/sketch would be best). Why is H20 most dense at 4 degrees Centigrade? Explain.

    5. Compare the three (3) procedures for the purification of water for bottled water. Which is the BEST? (in your opinion - and explain). Which toxins are present in Dallas water? Are the levels safe - how can you be sure? Is bottled water really safer? Explain with documentation. You may need to go to the internet for sources for this.

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    Solution Preview

    1. The viscosity or (fluid friction) varies with the material and with the temperature. The higher the temperature the lower is the viscosity. The viscosity of multi-weight motor oil is specified using two numbers. The first number is the viscosity when the oil is cold. This is followed by the letter W (which stands for winter, not weight), which is followed by the number that indicates the viscosity when the oil is at operating temperature. The higher the number, the thicker is the oil because the intermolecular bonding is stronger. This is why a 10-30 weight motor oil is better to be used in winter (because it is thinner) and 20-40 weight oil is better to be used in summer, so that high summer temperatures can lower the viscosity and make it easier to flow.

    2. Surface tension always decreases with increasing temperature. The formula is
    ST = H + T(d[ST]/dT), where ST is the surface tension, H is the energy required to increase
    the area of the surface of the liquid in contact with air, T is the absolute temperature in Kelvin, and d[ST]/dT is the change in the surface tension per degree increase in the temperature. The energy term, H, is always positive and The term (d[ST]/dT) is always negative. In winters, because of lower temperature, the ...

    Solution Summary

    This solution contains in-depth explanations to the respective questions on the comparison of chemical and compound properties. All necessary formulas and explanations are included to illustrate concepts.