Summary Add dry ice (solid carbon dioxide) to warm water and observe a dramatic state change from solid to gas. Science content Chemistry: States of Matter, Properties of Materials (K-7) Lessons activity is in Heat and Rates of Reaction Dry ice activities States of Matter and State Changes Resource Dry ice source Materials dry ice in styrofoam box, see reference for source thick glove (e.g. gardening glove) to handle dry ice tub or tray of warm water for a group of 3-4 students Procedure Show students a chunk of dry ice (only hold with thick gloves, as it will give cold burns to skin). It is carbon dioxide in its solid state and is very cold, -80ºC! The solid carbon dioxide does not stay solid very long in a warm room, but instead of turning to a liquid then a gas, it turns straight into a gas - called “sublimation”. The gaseous carbon dioxide can be seen as white clouds surrounding the solid chunk of dry ice. For each student group around a tub of warm water, drop in a few nuggets of dry ice. The students must not touch the dry ice. The warm water will dramatically speed up the state change from solid carbon dioxide to gas: large bubbles of carbon dioxide gas form in the water. At the surface, warm water that has evaporated comes in contact with the cold carbon dioxide gas and re-condenses into tiny droplets, forming white clouds. The white clouds, a mixture of water droplets and carbon dioxide gas, spill over the sides of the container and fall to the ground (as carbon dioxide is heavier than air). If the reaction slows before the dry ice is used up replace the water with more warm water. If you allow most of the dry ice to sublimate in the tray, small pieces will float to the surface of the water, and spin and zoom around. As gas projects from one side, it pushes the dry ice it in the other direction (Newton's Law of action and reaction). If the gas comes from an angle it will start it spinning. It behaves as a hovercraft does - the gas escaping from the bottom of the dry ice piece makes a layer of gas between the dry ice and water, so that it can skim with very little friction over the surface of the water. The small pieces are safe to touch briefly, so students can redirect the direction of the dry ice pieces with a light touch. Grades taught Gr 2 Gr 3 Gr 4 Gr 5
