Notice that K does not use a degree symbol. If the thermometer is to measure temperature on the Kelvin scale, the ice-water reference point is labeled 273.15 K, the boiling-water reference point is labeled 373.15 K, and the distance between these two marks is divided equally into 100 segments. The distance between these two points is divided into 180 equal segments. If the thermometer is to measure temperature on the Fahrenheit scale, the reference point for the ice-water mixture is labeled 32☏ and that for boiling water is labeled 212☏. The distance between these two reference points is divided into 100 equal segments. If the Celsius scale is to be used, the reference point for the ice-water mixture is labeled 0☌ and that for boiling water is labeled 100☌. Another mark is made on the column at this level this mark is a second reference point.įurther steps depend on whether this thermometer will measure temperature on the Celsius, Fahrenheit, or Kelvin scale. The ice-water mixture is then heated to boiling and kept at that temperature while the height of the mercury in the column rises to a new constant level. When the height of the mercury in the column remains constant, a mark is made. First, the mercury bulb of a new thermometer is immersed in a mixture of ice and water. This increase in height is proportional to the increase in temperature.Ī thermometer is calibrated in the following manner. When the temperature increases, the mercury expands and its level in the capillary tube rises. In order to measure its expansion or contraction, the mercury is confined within a small, thin-walled glass bulb connected to a very narrow or capillary tube. In the thermometer with which you may be most familiar, the substance that expands and contracts is mercury. Two essential features of a thermometer are: (1) it contains a substance that expands when heated and contracts when cooled, and (2) it has some means to measure the expansion and contraction. The relationship between temperatures on these three scales is straightforward if you understand how a thermometer is constructed and calibrated. Temperature is measured with a thermometer and is most commonly reported using one of three different scales:įahrenheit (F), Celsius (C) (sometimes called centigrade), and Temperature measures how hot or cold a sample is relative to something else, usually an arbitrary standard. Let us consider temperature before discussing its relationship to the energy of a sample. The amount of heat energy associated with a particular sample is dependent on its temperature, its mass, and its composition. The large calorie (Calorie) used in nutrition is equal to one kilocalorie. The terms kilojoule (kJ), 1000 J, and kilocalorie (kcal), 1000 cal, are also commonly used. Energy is measured either in joules (J) or in calories (cal), where the conversion factor relating the two units is: In this section we examine properties related to energy. We have discussed properties related to the mass and volume of a sample of matter. We have learned that chemistry is concerned with the properties of matter and with the energy changes that matter undergoes.
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