Measurement

Unit Summary

In Unit 3, 2nd grade students build on their understanding of length and measurement by learning about standard units of measurement and tools used to measure objects. In first grade, students measured indirectly and by iterating length units. In this unit, students are introduced to the metric units centimeters and meters. Students use rulers to measure objects on paper and in real-life. They then connect this idea of measurement to the number line, exploring similarities and differences between rulers and number lines. Students represent whole numbers as lengths on a number line and they use a number line to represent sums and differences within 100. Given their growing understanding of measurement and number lines, students then display measurement data on line plots and answer questions about these line plots. 

In Topic A, students are introduced to centimeters by using a one's base ten block which measures 1 centimeter. They use centimeter cubes to iterate a centimeter unit, building on their Grade 1 work and extending this to make their own centimeter ruler (2.MD.A.1). As they explore measuring with standard measuring tools they come to understand that when measuring they start at zero and measure an object to its endpoint on a ruler. They also come to understand that the distance between each tick mark on a ruler represents a standard unit, so in the case of a centimeter ruler, the distance between each tick mark represents a centimeter. 

As students develop their measuring skills they use benchmarks to estimate and check their measurements with centimeter rulers (2.MD.A.3). They further expand their measurement knowledge by learning about different tools such as meter sticks and tape measures to measure different objects and learn to select appropriate tool to measure based on the object they are measuring. As their work in Topic A continues, students learn how to measure and compare objects of different sizes and express the difference in terms of standard unit of measure (2.MD.A.4). Instead of simply recognizing an object as longer or shorter, students represent the difference in terms of centimeters or meters. Students also use their knowledge of measurement to solve word problems involving length within 100 (2.MD.B.5). 

In Topic B, the focus shifts to their understanding of number lines. Now that students understand the distance between tick marks on a ruler represents a standard unit of measure, they can equate that to the more abstract version on a number line. Through this topic students represent lengths from zero on a number line and based on intervals are able to identify missing tick marks on a number line when counting by 1s, 5s, or 10s (2.MD.B.6). Students are also able to use given tick marks to estimate whole numbers on a number line. The work of this topic builds on their skills of counting within 1,000 (2.NBT.A.2).

In Topic C, students put their knowledge of measurement and number lines together to generate measurement data and create line plots. Students measure real world objects and create line plots to show the measurements of objects to the nearest whole unit (2.MD.D.9). Using a horizontal scale students mark x’s to represent each object that measures that same length and then answer questions based on the generated line plot. 

The work of this unit connects to work students will do in units 4 and 5 where they will continue to use number lines to place and order numbers as well as use them as a tool to represent addition and subtraction. In Unit 6 students will build on their measurement skills as they apply them to customary units. They will further build their understanding of measurement and the understanding that the length of the unit affects the measurement of an object in situations where you are measuring an object using two different standard units of measure (2.MD.A.2). 

In future grades students will continue to iterate on their understandings of measurement and number lines as they expand to looking at non-whole units of measure and expand their number lines to negative numbers, the core foundations of which can be seen in the learnings in this unit.