Measure 32 — Math 7

Measurement

Child shows increasing understanding of measurable properties such as length, weight, and volume and how to quantify those properties

Formal measurement involves repeatedly applying a unit (such as an inch or pound) to a continuous quantity and assigning a number (such as three inches; ten pounds) to that quantity. Preschool children have not developed the requisite knowledge and skills to quantify and measure such properties as length or weight accurately by formal measurement. However, they know a great deal about measurable properties such as size, length, weight, and capacity; and they develop an informal/intuitive understanding of measurement that involves evaluating and comparing things based on these properties. From a very early age, young children notice and explore the measurable properties of objects and compare them. Their initial, informal efforts to measure are primarily perceptual—that is, they compare and make judgments about relative properties based on how things look. Older preschoolers begin to develop strategies for comparing and measuring things that are appropriate to the properties being compared. This is a critical stepping stone to accurate measurement.

Infants are sensitive to the dimensional properties of things they see, hear, or feel, including features such as size (of objects, for example) and intensity (of sound or light especially). They react to novelty in size with increased attention, by staring intently at a balloon that is being inflated, for example. Older infants explore and learn about such properties as size, weight, and capacity in their play with objects. They react to and interact with objects differently on the basis of size or amount.

Toddlers begin to understand and use words that refer to measurable properties of things, such as “big,” “little,” “loud,” and “heavy.” They use these terms categorically to name single things, for example, “big dog,” or “little boy.” They also begin to understand and use terms like “big” and “little” in simple comparisons. For example, a child might correctly indicate that a doll’s shoe is little and his shoe is big.

Young preschoolers commonly evaluate and compare objects and people (including themselves) to find out how big, tall, deep, or heavy things are. For example, children make simple size comparisons to find the right block to complete a structure or to find a dress to fit the smallest doll. Or a child might explore the property of weight by dumping water from a bucket until it is light enough to carry, or investigate depth by digging a deeper and deeper hole. Young preschoolers also understand and begin to use simple words that specifically refer to the relative size, length, or weight of objects, such as “bigger,” “smaller,” “longer,” or “taller.” Still, the measurement comparisons of young preschool children are based primarily on direct perceptual information, particularly on how things look.

Older preschoolers begin to move beyond using primarily perceptual/visual measurement to using strategies that enable them to compare two things (by length, weight, capacity, or some other measurable dimension) that are not obviously different. One such strategy is direct comparison. For example, the weight of two objects can be directly compared by holding one in each hand and testing their weight or by using a balance scale. The length of two objects that are very close in size can be compared by placing them side-by-side so that the objects are aligned at one end. Knowing to line up the two ends before comparing the objects’ lengths is critical to this strategy. Once this strategy is learned, young children can compare and order two, and even three, objects by length or height. Young children may also try using standard tools (rulers, scales, measuring cups) or non-standard tools (blocks, pieces of string) to measure things. This may involve using a non-standard unit, such as hands or paper clips, to determine how many hands- or how many paper clips-long something is. Some older preschoolers may also learn how to use an intermediary unit (such as a piece of ribbon or string) to compare two things, for example, by using a rope to compare the length of two sides of the sandbox.