Q1.
Put an ice cube in a cup, leave it on the table and observe. What can you conclude from the observations?
Answer
Observation: the ice cube slowly becomes smaller, loses its sharp edges, and after some time only water is left in the cup. No new material appears and nothing is left over.
Conclusion:
- Ice changes into water on its own when it is kept in a warm room. This change is called melting.
- The change happens because the ice takes heat from the room air and from the cup. Ice melts at 0 °C, and a room is much warmer than that.
- Since ice turns wholly into water and nothing else, ice and water must be forms of one and the same substance.
Why it happens: in ice the particles are held in fixed places and can only vibrate. Heat from the room makes them vibrate harder, until they break out of their fixed places and begin to slide over one another — the ice becomes water.
Try This: Put one ice cube in a cup on the table and an identical cube in a cup inside a cupboard. The cube on the open table melts sooner, because it gets heat faster. Do not keep one in the sun and one in shade for this test — change only one thing at a time.