(a) Distinguish between heat and temperature.
(b) State two physical properties of substances which may be used to measure temperature.
(c) State two reasons why mercury is preferred to alcohol as a thermometric liquid.
(d)(i) Describe how a mercury-in-glass thermometer is calibrated.
(ii) State two precautions necessary to ensure an accurate result.
(e) Explain how land and sea breezes occur.
Explanation
(a) Heat is a form of energy due to temperature gradient while temperature is the degree of hot-ness or cold-ness of a body.
(b)(i) The change in volume expansion of a fixed mass of a liquid.
(ii) The change in volume of a gas at constant pressure.
(iii) The change in electrical resistance of a substance.
(iv) The change in e.m.f generated in a thermo-couple. (Note: Any correct two)
(c)(i) It does not wet glass (unlike alcohol) (ii) It is opaque and easily seen (unlike alcohol) (iii) It is a
better conductor of heat. (iv) It measures higher temperature than alcohol. (Note: Any correct two)
(d) Support the thermometer vertically ensuring the bulb is covered with melting pure ice shavings. Allow the mercury thread to fall till its level remains steady. Mark this position on the thermometer as the lower fixed point. Suspend the thermometer in the steam of a hypsometer. Allow the mercury thread to rise until its level remains steady. Mark this position on the thermometer as the steam point. Sub-divide the fundamental interval into a number of equal parts. Precautions
(i) The thermometer bulb should not be placed in the boiling water of the hypsometer.
(ii) The thermometer should be inserted in the hypsometer such that the mercury thread is visible just above the top of the apparatus.
(iii) Some few minutes should be allowed to pass when the mercury thread is steady before making the thermometer.
(iv) One should ensure that the steam is at atmospheric pressure. (Note: Any correct two)
(e) The breezes are due to the fact that the specific heat capacity of water is greater than that of land. During the day the land is hotter than the sea. A low pressure area is created on the land and cooler air from the sea blows into the land. This wind is called sea breeze. At night the sea is warmer than the land. A low pressure area is created over the sea, resulting in cooler air blowing from the land where the pressure is higher into the sea. This is called land breeze.