When we think of measurement, a couple of things may come to mind. We may think of numbers, or we may think about instruments or equipment. The scale shown above, for instance, is an example of a common instrument that is used in measurement. In this case, the scale is measuring the weight of citrus fruit. Adjacent to the fruit is a 1 kilogram weight. If we were getting fruit at the market, we would likely purchase fruit in weight equivalents, like a kilogram or a pound, or some fraction of these equivalents. Measurement, in this example, allows us to measure quantities of fruit in a reliable fashion. Can you think of other food items you might measure? You might measure the temperature of a casserole, or the volume of milk used in a recipe, or the weight of dough in a pizza. Measurements depend on estimates, like estimating the weight of fruit. These estimates depend on reference points or equivalents, like one kilogram or a fraction of a kilogram. We also use measurement frequently in our study of the chemical world. Much of our modern understanding of chemistry is based on our ability to measure various physical quantities of chemical species.
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