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# 3.MD.A.2

**Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l).**

^{1}Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem.^{2}

__Summary:__

This standard deals with the concept of capacity, or the amount that a container will hold. As students explore this concept, they will need to have a variety of hands-on opportunities to develop their understanding. They will also explore weight, with the understanding that the weight of an object tells how heavy it is, while capacity tells the potential amount that can be held within a particular container.__Understanding the Standard:__

__Understanding the Standard:__

- Fostering an understanding of such an abstract concept requires that students have ample opportunity to explore this standard using a variety of concrete models and experiences.
- In order for students to conceptualize these units, have concrete containers available for students to handle.
- Ask students to make predictions about the capacity or mass of various objects and then provide a learning lab where their predictions are tested.
- As students discover the capacity and mass of a variety of objects, ask them to record their findings in a math journal for later reference and classification.

__Questions to Focus Instruction:__

- Can students explain the concept of capacity?
- Can students estimate and make predictions concerning the capacity of two containers?
- Are students able to compare and order containers with varying capacities?
- Can students explain the concept of mass?
- Can students estimate and make predictions concerning the mass of two or more objects?
- Are students able to compare and order objects with varying masses?

__Skills__

**Prior to:**Students have distinguished the attributes of various containers and have estimated their capacity. They have had an introduction to terms that are related to capacity. Students understand that weight is the heaviness of an object and can be measured using a variety of units.

**Students have a more sophisticated understanding that capacity is not the actual weight (or heaviness) of an object, but rather the potential amount that a particular container may be able to hold. Additionally, they can use their mastery of the four operational processes to calculate the volume and mass of an object.**

At Grade Level:

At Grade Level:

^{1}Excludes compound units such as cm3 and finding the geometric volume of a container.

^{2}Excludes multiplicative comparison problems (problems involving notions of “times as much”; see Glossary, Table 2).