Water Properties Lab
Drowning Lincoln
• You just saw three important forces tugging on the water:
gravity, cohesion, and adhesion. Gravity flattens the
droplets, cohesion holds the droplets together, and
adhesion holds the drops on the surface of the coin.
The cohesive force is the pull of the water molecules on
themselves. Each successive drop sticks to the water that’s
already on the coin. We often call this cohesive force
“surface tension.” It’s what makes water drops look like
they’re wrapped in invisible skins. Soap reduces the
cohesive force, and breaks the surface tension. Soapy
water makes smaller drops than plain water. Since soapy
drops are smaller, more soapy drops will fit on a penny than
plain water drops.
1. Polarity of water.
• Pages 40 and 41
2: why does water climb a paper
strip….
• Page 41
3. Why do oil and water not mix
• water is polar
• oil is nonpolar.
• Cohesive forces between water molecules and
cohesive forces between oil molecules are
stronger than adhesive forces between water
and oil
• Oil floats on top of water because it is less
dense – the atoms are farther apart.
4. Explain how detergents act as
cleaning agents…
• Detergent and soap
molecules have a polar
end and a nonpolar end
- The polar end attaches to a
water molecule
- The nonpolar end attaches
to oil or dirt
- Dirt and oil can be rinsed
away
5. Skip
6. Water is known as the universal
solvent
• Human body is 66% - 75% water by weight
• Suspends red blood cells to carry oxygen to body
cells
• Solvent for the electrolytes and nutrients needed by
the cells
• Solvent for carrying waste material away from the
cells