Last week’s Children’s Museum of Houston’s “O Wow Moment” as shown on KPRC Channel 2 dealt with phase changes, specifically melting – when a solid (like ice) becomes a liquid (like water). There are 5 different states, or phases, of matter the three main ones being solid, liquid, and gas. When a substance changes between the phases, usually by adding or removing heat, we have a phase change. When a substance changes phases, it either needs to have energy added or removed, even though the temperature of the substance doesn’t change. To prove this, we conduced a little experiment:
What to Do:
- Cool some water down to about 32° F (0°C) using your freezer or extra ice.
- Measure around a cup of water and find the weight (you’ll see why in a moment).
- Pour it into a pot on the stove and turn the temperature to high.
- Time how long it takes to boil.
- Take the pot off, pour out the water, and let the pot cool down to room temperature.
- Raise the temperature of some ice to 32° F (0°C) by placing it out at room temperature. Note that some will melt, so you will need to make sure you only use unmelted ice.
- Measure out equal weight of ice as the water you used earlier. This way, when the ice melts, you have the same amount of water being heated.
- Pour the ice into the pot on the stove, turn the temperature to high, and time how long it takes for the ice to melt and reach boiling.
What’s Happening?
Even though the ice and water are at the same temperature, ice has bonds that hold its molecules in a crystal pattern. In order to break the bonds and melt the ice, extra heat energy is needed. So, even though the temperature doesn’t rise, heat is absorbed to melt the ice which is why it will take longer for the ice to first melt and then boil.
