The state of matter of a liquid changes when it becomes frozen; it turns into a solid. Whether you're a teacher or a parent, explore this phenomenon by engaging children in activities that allow them to investigate frozen liquids in a hands-on manner.
Explore how fast different liquids freeze. Provide children with a variety of different liquids and ask them which liquid they think will freeze the fastest; write down their predictions. Examples of liquids include pure water, soda, orange juice and lemonade. Set each of the liquids in individual sections of an ice tray and place them in a freezer. Check on the ice tray at different intervals of time to see if any of the liquids have frozen. Make sure you note the amount of time that has passed from when you first put the liquid in the freezer. Once one of the liquids has frozen, remove the tray and test the remaining liquids to see how frozen they are. Out of the four liquids provided, the pure water will be the first to freeze; discuss with children why this is.
Test which material melts ice the best. Discuss how during the winter, different materials are used to melt ice to prevent cars and people from slipping. Ask children if they can list some of the materials that are used to melt ice -- salt, sand and kitty litter are some of the most common materials. Set out ice cubes on individual plates and provide students with the three materials listed. Instruct them to sprinkle the materials onto the ice cubes and to watch which one melts the ice the quickest. Discuss the results.
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Water and Oil
Water and oil usually don't mix; when they are combined, the water sits on the bottom of the container and the oil sits on top. When the two are combined and frozen the liquids reverse their order in the container. Set out the two liquids and ask children to predict what will happen when they are combined. Instruct them to pour the two liquids into clear containers and watch what happens -- the water will sink to the bottom of the container and the oil will sit on top. Explain that this happens because water molecules are denser than oil. Ask children to predict what will happen if the liquids are frozen. Once frozen, the water will rise to the top of the container because it is less dense than the oil in its frozen form. Have them experiment to see if the same thing happens when oil is mixed with other liquids -- soda, sugar water and juice, for example. Instruct them to mix oil and the mentioned liquids in separate containers, observe if the liquids separate and if they change places when frozen.
Study how and why ice flips while it's melting. Create bi-colored ice cubes by filling ice trays half way, adding food coloring to the trays and freezing them; once the colored half cubes are frozen fill the rest of the tray with extremely cold water and set it back in the freezer. Remove the ice cubes and place them in a glass or bowl of warm water. Ask children to observe as the ice cubes flip over as they melt -- the colored side will point up, then the clear side, then the colored side and so forth until the cubes are melted. Explain that this is happening because as the ice melts, the top part, which isn't exposed to the warm water, remains heavy and flips over in the water. This continues to happen until the ice is totally melted. After observing with the water ice cubes, experiment with ice cubes made from different liquids. Create half water and half soda, milk and juice ice cubes. Have children predict if the cubes made with different liquids will flip when placed in water, as the water cubes did. Set the different cubes in water and have children prove or disprove their predictions by observing what happens.