Name ________________________________________
HO# ____
Density Tank Lab
Investigation One: Density differences between salt and fresh water
1.
2.
3.
4.
Take a container of fresh water and weigh it on a scale.
Record its weight: ______ounces
Pour the salt from the small container into the water.
Write a hypothesis of what will happen to the density of the water when the salt is
added to the fresh water. Hypothesis: If …then … because …
Record your hypothesis here. ______________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
5. Add the salt to the fresh water and weigh the mixture again. Record the weight here:
________ ounces
6. How does the addition of salt affect the weight of water? Explain.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Which is denser?
In the following investigations, how will you know if one solution is more dense than another?
The solution that is denser will: ___________________________________________________________
Investigation Two: Variable = Temperature: Density of cold water (blue) vs. warm water (red)
7. Write a hypothesis of what will happen when you place cold fresh water in one
side of the density tank and warm fresh water in the other side of the tank and
then remove the divider. Hypothesis: If …then … because …
a. Record your hypothesis here. ___________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
b. Draw a model of what you observed:
c. Explain why this happened.
____________________________________________________________________________________
____________________________________________________________________________________
d. Which is more dense (circle one)?
cold water
or
warm water
Investigation Three: Variable = Salinity
Density of room temperature salt water (green) vs. room temperature fresh water
8. Write a hypothesis of what will happen when you place room temperature salt water
in one side of the density tank and room temperature fresh water in the other side of
the tank and then remove the divider. Hypothesis: If …then … because …
a. Record your hypothesis here. ____________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
b. Draw a model of what you observed
c. Explain why this happened.
____________________________________________________________________________________
____________________________________________________________________________________
d. Which is more dense (circle one)
salt water
or
fresh water?
Investigation Four: Variable = Percent Salinity Density of room temperature salt water – 10%
SALINITY (green) vs. room temperature salt water- 20% SALINITY (blue)
9. Write a hypothesis of what will happen when you place room temperature salt water
with 10% salinity in one side of the density tank and room temperature salt water with
20% salinity in the other side of the tank and then remove the divider. Hypothesis: If
…then … because …
a. Record your hypothesis here. ____________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
b. Draw a model of what you observed
c. Explain why this happened.
____________________________________________________________________________________
____________________________________________________________________________________
d. Which is more dense (circle one) 10% salinity water (green)
(blue)water?
or
20% salinity
Investigation Five: Variable = Temperature Density of room temperature fresh water (green)
vs. cold fresh water (blue) vs. warm fresh water (red)
10. Write a hypothesis of what will happen when you place room temperature fresh water
in one side of the density tank and cold fresh water in the other side of the tank and
then remove the divider. Then once the divider is removed, place warm fresh water
in the container with the room temperature water and cold water. Hypothesis: If
…then … because …
e. Record your hypothesis here. ____________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
f. Draw a model of what you observed first (only room temperature and cold fresh
water)
g. Draw a model of what you observed when the warm fresh water was added to the
tank.
h. Explain why this happened.
____________________________________________________________________________________
____________________________________________________________________________________
Order the following from most dense to least dense: room temperature fresh water , cold
fresh water and warm fresh water (red)
Most dense ________________________
________________________
Least Dense ________________________
Sum It Up:
Think about this…The layers of different temperatures and densities of waters in the ocean
act as a barrier for the exchange of nutrients and dissolved gases between the top layers of
sunlit water ( where phytoplankton thrive) and the deeper nutrient rich waters.
More on back
Question: What needs to happen in these waters in order for the phytoplankton to get the
nutrients they need?
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________
Define the term upwelling (refer to your vocabulary list).
__________________________________________________________________________________________
How do upwellings relate to density? _____________________________________________________
__________________________________________________________________________________________