Comparing Weight and Capacity — Balance Pan and Pouring Cups

Read-aloud: Tomie dePaola's 'The Popcorn Book' excerpt (the page about kernel size vs popped size). 'A small cup of unpopped popcorn makes a BIG bowl of popped popcorn. Same popcorn — different amount of SPACE. That's CAPACITY.' Cultural note: 'Popcorn was first discovered by Indigenous people in the Americas, including the Aztec people of Mexico.'

• Show a cup of unpopped corn and a (separately prepared) bowl of popped
• Honor the Indigenous origin briefly
• Connect to today's work: 'We measure how much things weigh (with a balance) and how much they hold (with cups).'

Today we measure two NEW things: WEIGHT (how heavy) and CAPACITY (how much it holds). For WEIGHT, we use a BALANCE PAN. (Hold up balance pan.) If I put an apple on one side and a feather on the other side, the side with the apple TIPS DOWN — apple is HEAVIER. The feather side goes UP — feather is LIGHTER. If both sides are level, the objects have the SAME WEIGHT. (Demonstrate.) For CAPACITY, we use the POUR test. (Show 3 identical clear cups.) I fill Cup A completely with rice. Then I pour the rice into Cup B. If the rice fits exactly, they hold the SAME. If rice overflows out of Cup B, Cup A held MORE. If rice doesn't fill Cup B, Cup A held LESS. CRITICAL: this works perfectly when the cups are the SAME SHAPE. (Show example of two different-shape cups; pose: 'How would we know?' — answer: we have to pour to find out.)

• Heavier side TIPS DOWN.

  model Apple side tips down. Apple is heavier.

  prompt Balance pan: apple vs feather
• Small differences still show on the balance.

  model Pencil side tips down slightly. Pencil is heavier.

  prompt Balance pan: pencil vs eraser
• Identical cups = same capacity.

  model Rice exactly fills Cup B. Same capacity.

  prompt Cup A (full) pours into Cup B (identical, empty)
• Don't judge by HEIGHT — judge by POUR.

  model Rice fits and there's room left. Cup B holds more.

  prompt Cup A (tall, narrow) pours into Cup B (short, wide)

• If the apple side tips DOWN on the balance, which is heavier? (Apple.)
• Two cups look very different — one tall, one wide. How do we know which holds more? (Pour test.)

M-K-S-GM-15-A Photograph

Studio photo of a child-height table with a wooden balance scale (two pans on a beam). Left pan contains one red apple. Right pan contains a single white feather. The apple side has dipped down dramatically; the feather side is high in the air. Caption below: 'The apple is HEAVIER than the feather. The heavier side tips DOWN.' Style: clean lighting, white background.

M-K-S-GM-15-B Video Physical / non-image

Top-down camera. First half (0-22 seconds): two IDENTICAL clear plastic cups labeled A and B. Hand pours rice from full Cup A into empty Cup B. Rice exactly fills Cup B. Voiceover: 'Same shape, same fill — same capacity.' Second half (22-45 seconds): a tall narrow cup labeled A (full) and a short wide cup labeled B (empty). Hand pours from A into B. Rice fits in B with extra room. Voiceover: 'Different shapes — Cup B holds MORE than Cup A. Don't judge by height — judge by POUR.' Music: gentle xylophone.

• Weight station: each pair compares 3 object pairs on the balance pan. Record: 'A is heavier than B' / 'A is lighter than B' / 'A and B are the same weight'.

  scaffold Pre-labeled object pairs with weight relationship in teacher's notes for verification.
• Capacity station: each pair compares 2 cup pairs (one identical-shape pair, one different-shape pair) using the pour test. Record: 'Cup A holds more' / 'Cup B holds more' / 'Same capacity'.

  scaffold Funnels available; tray catches spills.

• Compare two objects (provided) by weight. Which is heavier? How do you know?
• Compare two cups (provided) by capacity. Which holds more?

• Math Detective close: 'Weight and capacity — measured by balance pan and pour test. Tomorrow we celebrate cultures of math!'

• Compare two things at home: one heavier, one lighter. Tell a grown-up. Bonus: find two cups at home and pour to compare capacity (with a grown-up's help).