## Weight, Capacity, and Temperature

Objects can be measured by a variety of their attributes. The attributes considered at this grade level are length, weight, mass, capacity, and temperature. There are two basic systems of measurement used in the United States, customary and metric. The units of weight in the customary system are ounce, pound, and ton.

One of the concepts that often causes confusion is the concept of capacity. It is the volume of an object expressed in units of liquid measure. In the customary system these units are fluid ounce, cup, pint, quart, and gallon. In the metric system, the most commonly used units of capacity are milliliter and liter.

It is important to distinguish between the concepts of weight and mass. Weight is affected by gravity. The less gravity, the less the object weighs. For example, the weight of an object on the Moon is about one sixth of the weight of the object on Earth. Mass is the amount of matter in an object. The mass of an object remains the same regardless of gravity. The most commonly used metric units of mass are gram and kilogram.

**Temperature**

A thermometer is used to measure temperature. Children may think of a thermometer as a vertical number line. In our customary measurement system, temperature is measured in degrees Fahrenheit. On the Fahrenheit scale, water boils at 212°F and freezes at 32°F. Normal human body temperature is 98.6°F.

Temperatures below zero are recorded as integers. The set of integers consists of the counting numbers 1, 2, 3, …, their opposites, −1, −2, −3, …, and the number 0. At this grade level, there is no need to discuss temperatures below zero unless mention of them arises from a natural situation, such as on a very cold day. Children will learn more about integers in future grades.

**Teaching Model 18.8:** Reasonable Answers