Water properties

Activity 1: penny drop Wash and rinse a penny in tap water. Dry it completely with a paper towel. Place the penny on a flat surface. The flatter the surface is, the better this experiment is going to go. Use an eyedropper or pipette to draw water and, carefully, drop individual drops of water onto the flat surface of the penny. Keep track of the water drops as you add them, one at a time, until water runs over the edge of the penny. You’ll probably be surprised by the number of drops you get on there. Repeat the experiment by testing another liquid. Use the table below to keep track of your trials and liquids.

Activity 2: surface tension What You Do: Start with a cup of water and some paperclips. Do you think a paperclip will float in the water? Drop one in the cup to find out. Now find out if you can use surface tension to float the paperclip. Instead of dropping the paperclip into the cup, gently lay it flat on the surface of the water. (This is tricky — it may help to place a piece of paper towel slightly bigger than the paperclip in the water. Then lay the paperclip on top of it. In a minute or so, the paper towel will sink. Observe what happens with the paper clip. Now put a drop of dish soap in the water. Observe what happens with the paper clip. Explain what happened with the paper clip and provide a possible explanation.

Activity 3: Homework (lab) freezing point Have you ever wondered why rivers and lakes freeze in the winter, but oceans do not? In this experiment we will see that it is the presence of salt in the ocean that makes it less likely to freeze. What You Need: 1-gallon freezer bag 1-quart freezer bag crushed ice salt thermometer What You Do: Fill the gallon freezer bag half full with crushed ice. Add one cup of salt and seal the bag. Put on some gloves and knead the ice and salt until the ice has completely melted. Use the thermometer to record the temperature of the saltwater mixture. Even though the ice has melted, the temperature should be less than 32°F (0°C). Now put about an ounce of water in the quart freezer bag. Seal the quart bag and then put it in the saltwater mixture in the larger bag. Seal the larger bag also and leave it until the water inside the quart bag freezes. How did the water freeze when surrounded only by saltwater?