Monday, July 16, 2012

Experiment 7: Making Rain

This experiment is fun, especially for elementary and preschoolers. We did it as a part of our study of the water cycle.

CAUTION: you must have adult supervision for this experiment as you are dealing with a stove top and boiling water. This experiment also demonstrates how temperature is one of the main factors in changing the state of matter.

  •  one hard covered book
  • stove top heating element
  • one small sauce pan
  • freezer
  • water

1) place your hardcover book in the freezer and allow it to sit there at least over night.
2) boil a pot of water (demonstrating evaporation)
3) once you have a cloud of steam rising from the pot, hold the book at an angle in the steam, making rain! - Watch out for your fingers! Steam is very hot!!


  First in changing the states of matter: This is the approach to take with older kids who may already be familiar with the water cycle. In order to change a substance to different states of matter (liquid, solid, gas) you must apply a change in temp. A solid is a substance that has the molecules tightly packed together with stong bonds, at room temperature. A liquid is one where the molecules are spread out, some have bonds to other molecules, some are free floating. A gas is where the atoms/molecules float independantly from the other atoms, no bonds between them, rarely do they interact with the other atoms.

Water is one of the easiest to see the change in matter. If you apply heat, the liquid will evaporate, this results in steam - aka water vapor (a gas). If you apply a dramatic drop in temperature (like in a freezer) the h2o molecules will bond tightly together creating a solid (ice). Now, most children are taught these 3 states of matter at fairly young ages. But did you know there are actually 5 states of matter? The unsung heroes of matter are Plasma and the Bose-Einstein Condensiate (BEC). Plasma as a state of matter was only introduced in 1879, and the BEC was only recognized in 1995!! In a BEC the atoms are even more richly packed than in a solid. Most solids are brittle because of the way the molecules are bound (ever shattered a piece of ice?), but BEC are extremely strong, and not easy to break. A plasma is a cross between a solid and a liquid. It has properties of both.

Scientists are still hard at work on understanding matter. In fact, most scientists now refer to 'states of matter' as a Phase. For example, with water. If you start at a very low temperature you have a BEC, slowly increase the temp and youll have a solid (ice). If you slowly increase the temperature, you'll get a plasma (slushy like material, some ice, some water). Keep the temp increasing and you'll eventually get a liquid, keep the gem going and eventually you get a gas. So it is like your water has gone through different phases based on temperature. In a nutshell, matter is understood based on 2 things: temperature and the density of the molecules.

Water cycle: Did you know the amount of water found on Earth hasn't changed for billions of years? The only things that have changed are the location and whether or not the water is drinkable! The water cycle is responsible for both. It is never ending, which is why it is considered a cycle. At any given moment there are millions of gallons of water all around the globe: from oceans and seas (which contain a lot of salt); to lakes, rivers and ponds which are fresh water (low salt, but higher in other natural chemicals; to clouds, snow, ice and rain! Water is everywhere. To keep water moving about we rely on the water cycle. You see, the sun heats the surfaces of most water (puddles, rivers, oceans etc.) the only water unaffected by this first stage is water found below the ground or ice. As the sun heats the water some molecules seperate and turn to water vapor, a gas. Since water vapor is lighter than air it raises high into the sky. Way up high in our atmosphere it is very cold, the water vapor then wants to bind back to a solid, but our atmosphere is vast, so the molecules have trouble finding eachother in order to bond. Istead the bond with dust particles. This is the reason for the awesome shapes of a snowflake. Many water molecules will bind with individual dust particles, growing into ever larger snowflakes (ice). The particles might even find eachother, creating clouds. But the sun strikes these atoms as well, melting the ice back to water, which is heavier than air so it falls back to the ground as rain. (in winter the snow/ice particles grow until they are too heavy to remain aloft and they fall as snow or ice!). Once the rain is on the ground it flows down stream, back to the oceans, rivers lakes, etc. Happy learning!!

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