Galilean Hydrostatic Density Thermometer

45 mins Ages 7-9 Indoor

An engaging, screen-free learning activity that builds real-world creativity and critical thinking for kids aged 7 to 9.

Materials Needed

  • • Tall clear glass cylinder or glass vase (1 unit)
  • • Small plastic snap-lid sample vials (3–5 mL) (2–3 units)
  • • Small steel paperclips (8–10 units)
  • • Liquid food coloring (1 bottle)
  • • Ice cubes and warm water (as needed)

Pro Tips

  • → Fill small plastic sample vials with colored water and add paperclip ballast until they barely float with neutral buoyancy.
  • → As water warms up, its density decreases, causing the neutrally buoyant glass or plastic bulbs to sink to the bottom.
  • → Chilling the outer water increases its density, causing the sunken bulbs to rise back to the top.

Safety First

Handle glass cylinders with care; use comfortably warm water rather than boiling water.

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Step-by-Step Instructions

1

Step 1

Fill a tall, narrow glass cylinder or tall flower vase with room-temperature tap water.

2

Step 2

Fill a small plastic snap-cap vial with colored water, adding paperclips to its base until it barely floats below the surface.

3

Step 3

Place the calibrated vial inside the tall cylinder and observe its baseline suspension height.

4

Step 4

Add ice to the outer water to observe the vial rise, then add warm water to watch it sink as water density decreases.

What they are learning

Thermal volumetric water expansion Density temperature dependence Neutral buoyancy equilibrium tuning