Knowledge Pays Off

Why is quartz used in watches?
Quartz is used in watches as it acts as a piezoelectric oscillator. As a potential difference is applied across quartz, stress is generated across the perpendicular faces of quartz crystal. It is known as reveres piezoelectric effect. The word piezo in Greek means pressure and, therefore piezoelectricity means pressure electricity. It takes place in some crystal like quartz which lack certain symmetrical properties. A mechanical stress produces an electric polarization and, reciprocally, an applied field produces a mechanical strain. So, this oscillator keeps watches ticking.
How do you test the presence of methanol?
Methanol does not respond to the iodoform test. In fact the test is given by ethanol and those alcohols which process hydroxymethyl group or CH(OH)- group or carbonyl compounds having acetyl functionality. Methanol can be detected by the oil of wintergreen test. In this test, 1-2 ml of methanol along with few crystal of salicylic are treated with concentrated sulphuric acid in a test tube which is then gently heated. A characteristic smell of oil of wintergreen (Iodex type) is obtained due to the formation of methyl salicylate.
Why is mercury used in thermometers despite being the poorest conductor of heat?
Most metals are good conductors of heat and they are solids at room temperature. Mercury is the only one in liquid state at room temperature. It's used in thermometers because it has high coefficient of expansion. Hence, the slightest change in temperature is notable when it's used in a thermometer. It also has a high boiling point which makes it very suitable to measure higher temperatures. Also it has a shiny appearance and doesn't stick to the surface of glass.
Why is glass transparent?
When light encounters a material, it can interact with it in different ways. These interactions depend on the nature of the light and the nature of the material. For instance, light falling on a leaf encounters many pigments molecules, predominantly chlorophyll. These molecules absorb light from the red and blue ends of the visible spectrum. The remaining light is scattered back because molecules in a leaf are tightly packed and so, we see a green leaf. Glass has properties of both a solid (its molecules don't move very much) and a liquid (the molecules are not arranged in any ordered way). Molecules in glass are not packed into a tight lattice and, unless tinted, it doesn't contain molecules that capture light with a particular energy. So, when light encounters glass, most o it passes straight through. Hence it is transparent.
What is quantum tunneling?
In Physics, quantum is the particle which obeys quantum mechanics. When a quantum particle has to cross a potential barrier which has more energy then the particle, than, according to the classical physics, it can not do so. But, in quantum mechanics, it can, however small it be. This phenomenon is known as quantum tunneling. The best example of quantum tunneling is the emission of alpha particles from a radioactive nucleus. Although the energy of alpha particles is less than nuclear potential, they can tunnel through it.