Floating in Salt Water

Buoyancy

Things You Will Need
• Pencil (shorter than glass)
• Thumbtack
• Glass of fresh (tap) water
• Glass of salt water
• Container of salt
• Marker

Do This

1. Stick a thumbtack into the top of the eraser of a pencil (to make it sink).
2. Place the pencil (eraser down) into the glass of fresh water. The pencil should float with its point above the water.
3. Mark on the pencil the water level where it floats in the glass of fresh water.
4. Now place the pencil (eraser down) into the glass of salt water.
5. Observe the difference in height that the pencil floats. Add increasing amounts of salt and mark the pencil each time.

What Should Have Happened

The pencil should have floated at a higher level in the saltwater solution. Objects are more buoyant in salt water than in fresh water. Because salt water has a higher density than fresh water, objects float easier or higher in salt water. Ships also float higher in salt water than fresh water.