CONVERTING SYSTEMS OF UNIT

Medical Chemistry Lecture By: Asst. Lect. Tariq Al Mgheer - College of Medicine- Babylon University CONVERTING SYSTEMS OF UNIT
To convert frpm the system of units used in the United States to Sl units, we must know the equivalents of the two systems. Table abov© lists the most widely used equivalents
To make use of the information in Table 3, we must convert the equivalents into
conversion factors. A conversion factor is simply the ratio of one unit divided by another. The relationship between any two units can be expressed as two conversion factors. For example, let us write the two conversion factors expressing the relationship between inches and centimeters. According to Table 3, 1 in, = 2.54 cm.
Whereas 1 cm = 1 / 2.54 = 0.3937 in. This conversion factor tells us that there are 2.54 cm per 1 in. The other conversion factor tells us that there is 0.3937 in. per 1 cm.
Example 1-1 Convert 5.00 in .to cm. The first step is to write the quantity that you want to convert, including its units:
5.00 in
Next, multiply this quantity by the conversion factor that allows you to cancel all
unwanted units:
5.00m. X (2.54/1 in ) =12.7 cm
The inches on top cancel the inches on the bottom, leaving cm as the desired unit.
Example 1-2 Convert 2.20 Ib to g.
Solution:
1 Ib = 454g.
The conversion factors are 2.20 Ib X (454 /1 Ib) = 999 g
TEMPERATURE
We determine how hot or cold an object is by measuring its temperature. We measure temperature by means of thermometers. The principle of a thermometer is based on the fact that most substances expand when heated and contract when cooled,
The most common type of thermometer is the mercury thermometer. Thermometers using other liquids such as alcohol can also be constructed. . •
To express the temperature of an object, the thermometer must have some kind