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5.3 Lab Report
Katherine
Density Investigation
Purpose/Problem:
What happens at the mouth of a river where the warmer fresh water enters the
colder seawater (an estuary)?
What happens when the saltier waters from the Mediterranean Sea empty into the
fresher waters from the Atlantic Ocean?
What happens to the water from an iceberg when it melts?
Introduction/Research:
Warm water is less dense than cold because the matter is faster and farther away
from each other. Salt water is denser than fresh water. Ice is less dense than water
because it floats, so when it melts the water level won’t rise. Density is the mass
divided by the volume.
Hypothesis:
If warm fresh water is less dense than cold salt water then the warm fresh water
will cool down and become denser merging with the cold sea water.
If fresh water is less dense than salt water then the salt will spread out and cause
the water to become less dense.
If an iceberg is less dense than the surrounding seawater then the water level won’t
rise because the water from the ice will become denser covering less space.
Materials/Supplies:
1 clear plastic container
1 extra mixing container (glass measuring cup) that measures liters and cups
Access to faucet with warm and cold water (kitchen sink)
45 ml salt
1 bottle food coloring
1 colored ice cubes (pre-made)
2.5 ml measuring spoon
Procedure:
I set up the materials for the first question for warm fresh water into cold salt
water. I filled the plastic container with ½ liter cold water and for the 36 ml a liter
salt for the salinity I added 18 ml salt. I poured ¼ cup warm water into the glass
measuring cup and added 3 drops of food dye to it. I poured the warm fresh water
into the cold salt water and recorded my observations as the water mixed together.
I washed out the glass measuring cup and the plastic container and dried
them for the next question of salt water into fresh water. I poured ½ liter of cold
fresh water into the plastic container. In the glass measuring cup I poured ¼ liter
cold fresh water and added 3 drops of food dye to it. For the salinity I added 9 ml
salt since 9 is ¼ of 36. I then poured the colored salt water into the fresh water and
recorded my observations as the water mixed together.
I washed out the glass measuring cup and the plastic container and dried
them for the next question of what happens to iceberg water when it melts. I poured
½ liters of cold water into the plastic container and added 18 ml salt to it for the
correct salinity. The pre-made ice cube had no salt in it (I questioned this) and it had
been frozen with 3 drops of food dye so it was colored. I took out the ice cube from
the freezer and carefully placed it onto the salt water. While the ice melted I
recorded my observations.
After my experiments were over I washed out the plastic container and the
measuring cup and put all of my materials away.
Observations and Data:
Pour ¼ cup colored warm water into ½ liter cold water with 18ml salt
The warm water spreads out completely over the surface and the salt water
is pushed to the bottom. The warm water moves to the top even if it falls to bottom
at first from being poured.
At the mouth of a river where warm fresh water enters cold seawater
the warm water spreads out on top of the ocean pushing the salt water down.
Pour ¼ liter colored water with 9 ml salt into ½ liter fresh water
The salt water moves to the bottom and spreads out completely. The salt
water spreads slower than the warm water spread over the cold salt water.
When salt water empties into fresh water the salt water ends up
under the fresh water and spreads out evenly.
Melt a colored ice cube (iceberg) into ½ liter cold water with 18 ml salt
Once the ice cube was put on the water the color spread a bit into the water
but then once the ice stopped moving around so did the color. The ice continued to
float and did not move around. Very slowly over the course of about 30 to 45
minutes the ice melted into the water. The ice water spread out over the surface of
the salt water. Everything stayed the same and once the ice was melted into the
water it did not sink to the bottom or move around. The salt water stayed at the
bottom and the ice water stayed where it entered at the surface.
When an iceberg melts the water from the ice stays towards the
surface and doesn’t move around much from the place it melted off of the ice.
Conclusion/Summary:
What happens at the mouth of a river where the warmer fresh water enters
the colder seawater (an estuary)? Cold salt water is denser than warm fresh water
so it will be heavier and move towards the bottom while the fresh water stays
towards the top half. My hypothesis was too vague and I did not give a clear
statement about the water but the water did not fully merge together. The salt water
stayed towards the bottom and the fresh water stayed towards the top.
What happens when the saltier waters from the Mediterranean Sea empty
into the fresher waters from the Atlantic Ocean? My hypothesis was a bit vague and
I predicted that the water would merge immediately. The water did not emerge
immediately and like in the first experiment the fresh water was still less dense than
the salt water and stayed towards the top half of the water mixture.
What happens to the water from an iceberg when it melts? My hypothesis
was correct but it was not broad enough to cover the full topic. With the currents
constantly moving the ice water would move around unlike in my closed
experiment but it would stay relatively at the same place in the top half of the water
because the cold water and salt would be about the same density.