A “fair test” investigation where the child predicts which of several identical ice cubes will melt first, depending on where it sits, and then watches the race play out over 10–30 minutes.
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Pop 3–4 identical ice cubes out of a tray. Place each one in an identical small dish (saucer or cupcake liner).
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Pick one variable to test — choose only one per session:
- Sun vs. shade (one in a sunny window, one on a shaded shelf)
- Metal vs. wood vs. plastic (each cube on a different surface)
- Plain vs. salted (sprinkle a pinch of salt on one cube only)
- Open air vs. wrapped in foil vs. wrapped in a wool sock
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Ask: “Which will melt first? Why do you think so?” Have the child place a numbered prediction card next to each cube (1 = first to melt, 2 = second, etc.).
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Set a kitchen timer for 5 minutes and check together. Repeat the checks every 5 minutes. Mark melting progress with a sticker on a chart.
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When the first cube is fully melted, declare the “winner.” Compare the order of melting to the child’s predictions. Talk about why the winner won.
Variation: add a thermometer (basic kitchen probe) for older or more interested children. Or run the race with flavored ice cubes (juice) so the puddles can be tasted at the end (allergen-checked).
Requirements
- Space: A table top with access to a sunny spot and a shaded spot
- Surface: Waterproof; place a tray under each cube to catch melt water
- Materials: 3–4 identical ice cubes, 3–4 identical small dishes or cupcake liners, prediction cards (numbered 1–4), a chart to mark melting progress, optional kitchen timer, optional materials for the variable being tested (salt, foil, wool sock, metal/wood/plastic plates, thermometer)
- Participants: 1 adult + 1 child
- Supervision: Light to moderate — set up takes 5 minutes, then the child can check independently between timed reads; supervise if a sun-window spot is used
Rationale & Objective
Phase-change observations are exemplary preschool science: the change is visible at child-scale, repeatable, and unfolds over a watchable timespan (Worth & Grollman; Eshach & Fried 2005). NGSS K-PS3-1 (“make observations to determine the effect of sunlight on Earth’s surface”) is a perfect curricular match for the sun-vs-shade variant. The activity hits HighScope’s Observing, Predicting, Experimenting, and Drawing conclusions KDIs in a single session and exposes the child to the foundational idea of a fair test — vary one thing, keep everything else the same — which Worth & Grollman explicitly use as a 4–6 year-old scaffold. The race format also builds the time-extended attention that briefer experiments do not.
Progress Indicators
- Early: predicts at random or always picks the same cube (“the one closest to me”); checks once and gives up; doesn’t connect the variable to the outcome
- Developing: predicts using one feature (“the sunny one will melt first because it’s warm”); waits through 2–3 timed checks; can describe what is happening (“it’s getting smaller”) but not yet why
- Proficient: predicts with a clear reason; tracks order across multiple checks; explains the result with cause-effect language (“the salt one melted first because salt makes ice melt”); sustains 15+ minutes
- Advanced: proposes the next test (“what if we put one in the freezer and one in the fridge?”); changes only one variable when designing it; records times with simple tally marks; remembers and applies findings (“last time the sunny one won”)
Safety Notes
- If using a sunny-window condition, beware of UV exposure for the child watching — EPA SunWise advises avoiding direct 10am–4pm sun for prolonged sessions; keep windows in shade or use indirect sun
- Salt can sting eyes and open cuts, and is unsafe to eat in the quantity used here — keep the salted cube on a separate plate, label it, and remind the child not to taste
- Cold-burn risk if the child holds a cube against bare skin for more than ~30 seconds — keep handling brief and offer a small dish to set it on
- Wet floors and tables become slip hazards — wipe melt water as it accumulates
- Skip food coloring on light fabrics, wood, or stone counters — some dyes are permanent
- If the child has Raynaud’s or any cold sensitivity, use insulated mittens or skip handling
Hints
- Playfulness: give each cube a name (“Cube A: Sunny Sam”). Make a finish-line drawing where each cube is a runner. Cheer on the winner
- Sustain interest: vary the test across sessions — never repeat the same variable two days in a row. Build a wall of “Race Results” so the child can compare across weeks
- Common mistake: changing more than one variable at once (sunny + salt + small cube). The child can’t isolate the cause and the inquiry collapses. Also: skipping the prediction step turns it into pure observation; without prediction there is no inquiry
- Limited space: an apartment kitchen counter and 4 saucers is enough. The whole activity fits in 20 minutes
- Cross-domain: count minutes (numeracy, time sense); rank cubes from fastest to slowest (ordering); describe shapes as they shrink (geometry); draw the cubes at each check (graphic recording)
- Progression: 2 conditions → 3–4 conditions → predict the order of finishing → measure with a timer → introduce a thermometer → design and run a self-chosen variable test
Sources
- Worth, K. & Grollman, S. (2003). *Worms, Shadows, and Whirlpools*. Heinemann / NAEYC
- Ashbrook, P. (NSTA *Science and Children* — "Early Years" column on ice and phase change); Ashbrook, P. (2016). *Science Learning in the Early Years: Activities for PreK-2*. NSTA Press
- Eshach, H. & Fried, M. N. (2005). "Should science be taught in early childhood?" Journal of Science Education and Technology
- NGSS K-PS3-1 and K-PS3-2 (effect of sunlight on Earth's surface)
- NASA JPL Education — "Melting Ice Experiment" lesson plan
- Boston Children's Museum *STEM Sprouts* — observation-over-time investigations
- HighScope KDIs — Observing, Predicting, Experimenting, Drawing conclusions, Communicating ideas
- Head Start ELOF — Scientific Reasoning (P-SCI 1, 5, 6)
- Teaching Strategies GOLD Objective 24 (scientific inquiry), Objective 26 (physical properties), Objective 27 (Earth's environment)
- EPA SunWise — UV exposure guidance for children