ICE and SALT ACTIVITIES
Has your child noticed that sometimes there is salt sprinkled on the ground to melt the ice in the wintertime? Well, salt plays a magical role in these great learning activities.
First, to establish a little background with your child, you might wish to set out two plates of crushed ice. Let your child sprinkle salt on one plate of ice and observe together which plate of ice melts first. Now your child will see that salt helps ice to melt.
This is because the sodium and chloride ions from the salt intermingle and dilute the water molecules. This makes it harder for the water molecules to join together to form ice crystals. Actually, it's still possible for the water molecules to form ice crystals, but now instead of freezing at 0°C, it's freezing point drops to below 0°C.
SMMART SCIENCE: MAGIC ICE
Now, for the activity, Fill a small glass with water and ice cubes. Give your child a piece of cotton string or yarn about a foot long. Let your child hold both sides of the string and rest the remaining middle part of the string on top of the icecubes. Take care to leave the ends of the string hanging over the edge of the glass.
Have your child count to 15. Now instruct her to take both ends of the string and pick it up, while lifting up a piece of ice with the string. The string is not attached to the ice and will not lift the ice.
Now, have your child lay the string back onto the ice with the ends of the string laying over the sides of the glass. Have your child sprinkle salt all along the string laying on the ice. Now count to 15 slowly.
SMMART SCIENCE: Color Ice Sculptures
Fill a disposable paper cup, cardboard milk carton, or other container with water and freeze over night. Let your child help you remove the ice from the container and place it on a cookie sheet to catch the melting ice water. Let your child sprinkle rock salt onto the ice and observe the ice melt more rapidly.
Check out the reason that the salt melts the ice more quickly at http://antoine.frostburg.edu/chem/senese/101/solutions/faq/why-salt-melts-ice.shtml. This site has a fun, interactive demonstration when you click “Add Solute” that further demonstrates this principle.
Now help your child drip drops of food coloring onto the top of the ice. The food coloring seeps through the cracks of the ice. You’ve created a beautifully colored, melting ice sculpture. Quick! Snap a picture before it melts away! (http://www.placeofourown.net/activity.php?id=137)