Unit Plan 18 (PreK Math): Compare Objects—Length & Weight

Focus: Directly compare two objects to decide which is longer/shorter, heavier/lighter, or holds more/less; use hands-on tools and clear comparison language.

Grade Level: PreK

Subject Area: Mathematics (Measurement Foundations)

Total Unit Duration: 5 sessions (one week), 20–30 minutes per session

I. Introduction

Children explore direct comparison by placing two objects side-by-side or using their hands to feel weight. They learn to use measurement words to tell which object is longer, shorter, heavier, lighter, or which container holds more/less. The emphasis is on noticing, describing, and justifying with simple demonstrations.

Essential Questions

• How can I tell which object is longer or shorter without measuring?
• How can I tell which object is heavier or lighter by feeling or using a balance?
• What words help me explain my comparison clearly?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Compare two objects directly to decide which is longer/shorter, heavier/lighter, or holds more/less.
2. Use side-by-side placement, hand hefting, or a simple balance scale to make and show a comparison.
3. Use measurement vocabulary to describe results (e.g., “The blue block is longer.”).
4. Explain or point to evidence that supports the comparison (what they did/observed).
5. Participate in safe tool use and cooperative talk during hands-on comparisons.

Standards Alignment — Custom CCSS-style Pre-Kindergarten

• PK.MD.2 — Directly compare two objects. Places objects side-by-side/in hand to compare length, weight, or capacity (e.g., “This stick is longer,” “This rock is heavier”). Aligns to: K.MD.2 (direct).
• PK.MD.1 — Describe measurable attributes (language foundation). Uses words like long/short, heavy/light, empty/full. Aligns to: K.MD.1 (language).
• Mathematical Practices: MP.1–MP.6 threaded (try, model, explain, choose tools, precise words, notice structure).

Success Criteria — Student Language

• I can place two objects together and tell which is longer/shorter.
• I can feel or use a balance to tell which is heavier/lighter.
• I can say my comparison using words like longer, shorter, heavier, lighter, holds more/less.
• I can show how I know (side-by-side, balance, pour to compare).