Name
Date
1.1 Act 2 WS 2
__ Core
How Sticky?
Watch the video at this link (in class or at home):
http://www.middleschoolchemistry.com/multimedia/chapter1/lesson1#water_balloon
1. Why do you think the water keeps its shape the moment the balloon is popped?
The water in the balloon sticks together. Cohesion, the water is attracted to
itself.
2. Imagine a drop of water hanging from your finger. How is this similar to the water
staying together after the balloon is popped? Explain.
This is similar because the water in the balloon is like a larger version of one
drop. In both, the water is attracted to itself, which keeps it together in a
similar shape.
3. Trevor put one drop each of water and rubbing alcohol on a piece of wax paper and
drew the results. Decide which of the diagrams shows the rubbing alcohol.
A is rubbing alcohol and B is water
.
How do you know? Explain
I know this because water is more attracted to itself. The stronger attraction
gives it a more pronounced dome shape.
4. Cohesion is the “sticking together of the same substance.” Does rubbing alcohol
or water demonstrate greater cohesion?
Water is more cohesive
How do you know? Explain
I know this because water stays together better than rubbing alcohol.
5. Adhesion is the “sticking together of different substances.” Should masking tape
be described as “cohesive” or “adhesive”?
Masking tape should be described as adhesive.
Why?
Masking tape sticks to many other materials. It also sticks to itself so it could
also be considered cohesive.
6. Look at the pictures shown to the right.
a. In which image is cohesion stronger than adhesion?
Cohesion is stronger in picture D
How do you know? Explain
The water drops are rounded and raised, the
molecules sticking to each other.
b. In which image is adhesion stronger than cohesion?
Adhesion is stronger in picture C
How do you know? Explain
The water molecules are spread out and not raised up as high, the water
molecules are sticking to the surface.
7. The pictures below show what should have happened during the CREEPY
CRAWLIES activity. In each case, explain how each liquid’s cohesion works with
its adhesion to rearrange it.
a. Corn oil and tap water:
For the above picture explain how each liquid’s cohesion works with its adhesion to
rearrange it.
Tap water adheres with greater force to the surface of corn oil than to wax paper.
The stronger attraction to the oil pulls the drop onto the corn oil puddle,
away from the wax paper. However, strong cohesive forces in the tap water
prevent the drop from breaking apart as it is pulled along
b. Corn oil and rubbing alcohol:
For the above picture explain how each liquid’s cohesion works with its adhesion to
rearrange it.
Rubbing alcohol adheres with greater force to the surface of corn oil than to wax
paper. The stronger attraction to the oil pulls the drop onto the corn oil
puddle, away from the wax paper. However rubbing alcohol’s cohesiveness is
too weak to prevent the drop from spreading out in the oil puddle.
c. Corn oil and soapy water:
For the above picture explain how each liquid’s cohesion works with its adhesion to
rearrange it.
Soapy water adheres with greater force to wax paper than to the surface of the
oil. With only very weak cohesive forces holding it together, the soapy water
spreads over the wax paper’s surface and soon soaks in due its stronger
adhesiveness with the wax paper.