Biology
Cells
Miss Chapin
Polar Vs Non-polar Lab
Background:
Lipids (fats, oils, and waxes) are non-polar substances that are not water soluble. This
means that they are not attracted to water (hydrophobic) and they do not react with many
other substances.
Polar substances, like water, reacts with many substances (by dissolving them) because
the negative side attracts to positively charged parts of molecules, and vice versa. In this
lab you will discover the some of the
effects of these properties.
Some substances, like soap, have both
a polar part of them and a non-polar
part. They are attracted to fats and oils
with their non-polar end, and to water
with their polar end. This gives them
the ability to surround an oil droplet
and make it more hydrophilic (water
liking).
Part 1: Pepper Pusher
 Get a Dixie cup of water and sprinkle pepper evenly over the top.
 Gently dip a clean finger into the center. What happens?

Now rub the end of your finger in oil and dip it into the water. What happens?

Now rub the end of your finger in soap and dip it in the water. What happens?

Explain why the water reacted differently to the different substances.
Part 2: Paper Clip Tip
 Get a shallow Petri dish and fill it with water. Using the tweezers, try balancing a
paper clip on the surface. Can you do it?

Now add a drop of soap to the water. What happens?
Biology
Cells
Miss Chapin

Repeat the same process, this time using oil instead of water. Can you make the
paperclip stay on top the oil?

Does adding a drop of soap affect it?

Explain your results. What do you think could be going on in each situation?
Part 3: Peanut Butter Batter
 Pour a small amount of oil into one Dixie cup and a small amount of water into
another.
 Using a clean craft stick scoop out a small amount and try to dissolve it in the cup
with oil. What happens?

Now get another clean craft stick, scoop out a little peanut butter, and try to
dissolve it in the cup with water. What happens?

Can you explain why peanut butter acts the way it does? (hint: peanut butter is
made primarily from penult oil)
Cleanup: part of your grade on this lab depends on how well you clean up after yourself.
IMPORTANT: DO NOT DUMP OIL OR PEUNUT BUTTER DOWN THE SINK;
IT CLOGS THE DRAIN!!!! Please dispose of extra oil and peanut butter in the trash.
You may however, dump the extra water down the sink. Also throw away the Dixie cups
and craft sticks and wipe down your work area.