ChemistryIce Melts and Water Freezes When Temperature Changes
Atlas stands at a sunny kitchen counter, holding a big ice cube in one hand and a cup of water in the other, watching a small puddle form as the ice drips.
- Identify that heating turns ice (a solid) into water (a liquid).
- Identify that cooling turns water (a liquid) into ice (a solid).
- Explain that water and ice are made of the same stuff, just in different forms.
- Predict what will happen to ice left in a warm room and to water put in a freezer.
- Compare the shape and feel of ice to the shape and feel of liquid water.
Key terms
- solid
- matter that is hard and keeps its own shape, like ice
- liquid
- matter that flows and takes the shape of its container, like water
- melting
- when warmth changes a solid into a liquid, like ice to water
- freezing
- when cold changes a liquid into a solid, like water to ice
- temperature
- how warm or cold something is, measured to know if it is hot or cold
Same Stuff, Two Forms
Ice and liquid water look and feel very different, but they are actually made of the exact same stuff: water. Ice is hard and keeps its own shape, while liquid water flows and takes the shape of whatever holds it. The only thing that makes one turn into the other is temperature. When you change how warm or cold the water is, you can switch it between solid ice and liquid water.
Warming Melts Ice
When ice gets warm, it melts, which means the solid turns into a liquid. Picture an ice cube on a hot sidewalk; soon it drips and becomes a puddle of liquid water. The warmth gives the tiny bits inside the ice more energy so they can flow instead of holding still. Melting always needs heat, which is why ice melts faster on warm days than on cold ones.
Cooling Freezes Water
When liquid water gets very cold, it freezes, which means the liquid turns into a solid. If you pour water into an ice cube tray and put it in the freezer, the cold pulls energy away from the bits until they lock into place and become hard ice. Melting and freezing can repeat over and over with the same water, so the water never disappears; it only changes form.
Worked examples
Predict what happens to an ice pop on a hot day.
- The day is hot, so warmth flows into the cold ice pop.
- Warmth melts solids, turning them into liquids.
- The ice pop melts and starts dripping as liquid.
Answer: The ice pop melts and drips because the warm day turns the solid into liquid.
What happens to water left in a freezer overnight?
- The freezer is very cold, so it pulls heat away from the water.
- Cooling a liquid enough makes it freeze into a solid.
- By morning the liquid water has frozen into solid ice.
Answer: The water freezes into solid ice because the cold freezer turns the liquid into a solid.
Activity
Sort each picture into the right box: Warm and Melting or Cold and Freezing.
Practice
Predict what happens to a snowman when spring sunshine arrives.
Explain why ice and water are made of the same stuff.
Common mistakes to avoid
- When ice melts the water is gone forever.The water is still there; melting just changes it from solid ice into liquid water.
- Ice and water are different kinds of stuff.Ice and water are the same stuff, and only the temperature decides which form it takes.
Check your understanding
You take an ice cube out of the freezer and leave it on the kitchen counter. What will happen?
You pour water into an ice cube tray and put it in the freezer. What will the water become?
Your friend says that when ice melts, the water is gone forever. Is your friend right?
Recap
Ice and liquid water are the same stuff in different forms, and temperature decides which form it takes. Warmth melts solid ice into liquid water, cold freezes liquid water into solid ice, and the water is never lost as it changes back and forth.
Reflect
Where have you seen ice melt or water freeze in real life?