The purpose of this activity is for students to learn that grams and kilograms are standard units for measuring weight. Students are introduced to the units using common objects as benchmarks. For each benchmark, students hold an object of some number of grams or kilograms and think of an example of an object that has about the same weight. Then, students look for items in the room that are in specific weight ranges. 

If time permits and if a scale or a balance is available, give students an opportunity during the Activity Synthesis to confirm the weights of the objects that they estimated. Depending on the number of weight measurement tools available, arrange for a whole-class weighing demonstration with the objects students chose, or arrange for students to weigh their chosen objects in groups, taking turns with each type of available tool.

• “¿Cómo describirías el peso del objeto en comparación con un gramo o con un kilogramo?” // “How would you describe the weight of the object compared to a gram or kilogram?”
• “¿Cuántos gramos o cuántos kilogramos crees que pesa?” // “How many grams or kilograms do you think it weighs?”

• Select students to share 1–2 examples from each column.
• Record responses on the poster labeled with the different categories.
• To familiarize students with the available weight measurement tools, display them for all to see, and consider asking:
  • “¿Qué observan? ¿Qué se preguntan?” // “What do you notice? What do you wonder?”
  • “¿Cómo leemos la balanza? ¿Qué pasaría si la balanza estuviera entre dos números?” // “How do we read the scale? What if the scale is in between two numbers?”
  • “¿Cómo leemos la balanza? ¿Qué pasaría si la balanza muestra un peso que está entre dos números?” // “How do we know when a balance shows that objects have the same weight?”
• If possible, allow students to use a scale or a balance to confirm the weight of some of the listed objects.
• If multiple scales are available, allow students to weigh their objects in groups. If only one scale is available, demonstrate it for the class.