The Ice Cube Experiment
Question:
Will ice melt faster at room temperature when in freshwater or saltwater?
Research:
Density:
a measure of how much matter there is in a given amount of space
how tightly packed the tiny particles that make up any substance are
higher density = more closely packed particles
both temperature and salinity affect density
Salinity:
the amount of dissolved salts that are present in water
high salinity = more particles = packed tight = high density
low salinity = fewer particles = spread out = less density
saltwater is more dense than fresh water
Temperature:
degree of hotness or coldness measured on a definite scale
high temperature = particles spread out = low density
low temperature = particles closer together = high density
cold water is more dense than warm water
Because ice is made up of fresh water, it fits into the less dense category in
terms of salinity
But because it is solid and cold, it fits into the high-density category in terms
of temperature
Hypothesis:
What do you think will happen?
Ice will melt faster in freshwater
Ice will melt faster in saltwater
Ice will melt at equal speed in both freshwater
and saltwater
Will temperature or salinity have more of an effect on
the density of the seawater?
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
Experiment:
Supplies:
• 2 clear cups
• Salt
• Water
• Ice
• Food dye (optional)
Instructions:
1) Use food coloring and water to make colored ice cubes.
2) Fill each of the clear cups with water.
3) Add salt to the first cup and mix to make saltwater.
4) The second cup will remain freshwater.
5) Drop one dyed ice cube into each cup at the same time for accurate
comparison.
6) Let cups sit until ice cubes are fully melted (approximately 10 minutes).
7) Record your observations and conclusion
Observations:
Record your observations over time. Please note changes that happen to both the ice
cube AND the water that the ice cubes are melting into.
Freshwater Observations Saltwater Observations
2 minutes
4 minutes
6 minutes
8 minutes
10 minutes
Conclusions:
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
Observations:
The cold fresh water from the melting ice is more dense than the warm water.
Cold water sinks so the warm water is always touching the ice cube. This makes
it melt faster.
The saltwater is more dense than the freshwater. Even though the ice cube is
colder than the saltwater, it cannot sink because the water beneath it is denser.
This means that the ice cube is always touching cold freshwater making it melt
much slower.
After about 10 minutes we can see that the ice cube in freshwater has fully
melted and the water has mixed so it is all the same color. However, the ice cube
in the saltwater formed a thin layer of the colored water at the top that did not mix
with the saltwater.
Conclusion:
Salinity is more important than temperature in determining the density of water.
