Science project idea on humidity and its affect on humans.
How the Amount of Moisture in the Air Affects Our Comfort
The effect of the amount of moisture in the air (humidity) upon our bodily comfort has been discussed under ventilation. It is the relative humidity rather than the actual humidity that affects us. The relative humidity is the ratio of the amount of water in the air to the amount which it can hold at a given temperature. A relative humidity of 50% means that the air contains one half of the amount of moisture that it can hold at that temperature. You will recall that damp days either in summer or winter are more uncomfortable than dry days of the same temperature. To understand this, we must consider how heat is lost from the body in winter and summer. What is the chief means 'of loss of heat from the body in winter? Explain the feeling of chill experienced on a damp day in winter, keeping in mind that moist air is a better conductor of heat than dry air. What is the principal way in which heat is lost from the body in summer? Explain now why we are more oppressed by the heat on a damp day.
The relative humidity of the air may be found by using the wet and dry bulb thermometer or psychrometer. This consists of two thermometers, one of which has a piece of wet muslin around its bulb. These are rapidly whirled in the air. Observations of the readings of the thermometers immediately after the muslin has become dry will show considerable difference. Explain. Tables have been prepared which give the relative humidity of the air corresponding to the difference between the dry bulb and the wet bulb thermometers at the different degrees of temperature. Another instrument for measuring the relative humidity of the air is the hair hygrometer. The human hair, when the oil has been removed, lengthens with dampness and shortens with drying. A hair prepared in this way is attached to a pointer which is moved across a dial as the hair changes in length. Use is made of the fact that paper or cloth impregnated with certain chemicals will change color as the relative humidity becomes greater or less. A paper flower, for example, which has been soaked in a solution of cobalt chloride and gelatine, will be violet in color when the relative humidity is high and blue when the air is dry.
Science Project Reports on Moisture in the Air 1. How railroads fight snow. 2. Origin of borax and other salt deposits in the West. 3. The salt supply of the United States.
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