 There are two types of measurement  Quantitative measurements have a definite form and are usually expressed as numbers with units. ▪ E.g grams, 12 liters, 4.5 grams/ml  Qualitative measurements are descriptive and have no numbers involved. ▪ E.g. It gave off a “reddish gas”, It had small bumps

 Measurements can be either direct or derived.  Direct measurement can be taken straight from an object. ▪ E.g. The length of an object in meters  Derived measurements must have a mathematical expression performed using several direct measurements ▪ E.g. The volume of an object is length x width x height

 Density is a very important derived measurement.  Density = Mass Volume Density is an example of an intensive property because it does not depend on how much of the object you have on hand.

 How do you know if your measurement are true or not?  Accurate measurements are measurements that are very close to the true value of a measurement.  Precise measurements are measurements that are consistent, but not necessarily close to the true value.  The goal is to have measurements that are both accurate and precise.

 Think of a dart board.

 The reliability of a measurement is expressed by the number of significant figures that are present.