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Liquid Density Applications
Name: Sonya H.
Status: Other
Age: 30s
Location: N/A
Country: N/A
Date: 2002
Question:
My nine year old son and I are working on his science
project. We have mixed three different types of liquids together to prove
that one liquid is more dense than the other, and will separate. In other
words, one liquid is heavier than the other.
I am having problem applying this concept to everyday life, on a level
where he can understand.
I would appreciate it, if you would give me some examples of why we need
to know the density of a liquid, and how is it used in everyday life.
Replies:
I am an engineer who deals with fluid systems. To me density is very
important when it comes to moving a fluid around. When I say fluid, I
mean both liquids and gases. Imagine if I want to pump water from point
A to point B. One of the important properties of the water is density,
because it determines what size pump I need to move it down the
pipeline. Now, imagine I want to pump ketchup from point A to point B.
It is more dense, so I need a more powerful pump to get it down the
line. Understand that density is just one of the properties that
determines how easy it is to pump a fluid from one place to another.
One example that your 9 year old would probably understand the best when
it comes to density of gases is a helium filled balloon. Helium trapped
in a balloon is less dense than the surrounding air and thus it rises.
Hope this helped.
Chris Murphy PE
Wow!! Where to start. 1. Many items in the grocery store are packaged by
volume, but sold by weight (potato chips for example). So are you getting
ripped off by just buying the biggest bag? 2. The WEIGHT of any object
floated on water is buoyed up by a force equal to the VOLUME of the fluid
displaced (Archimede's Principle). So some objects sink in pure water but
sink in salt water -- an egg for example. It's a matter of the density of
the object (egg) and the fluid (salt water).
The conversion from one to the other involves the density. 3. Submarines
float or sink depending upon how much their density is increases by taking
on ocean water ballast. 4. All "shots" in a doctor's office are delivered by
volume but are formulated by the weight of the active ingredients. The
conversion between the two is density. 5. A back yard grill that uses
propane as a fuel. The tank is filled with a certain weight of propane, but
the temperature of the grill is determined by the relative volume of gaseous
propane and air. Here we do not even do the calculation but still use the
concept.
Any place where one needs to be able to inter-convert from the volume of
something to its weight -- or the other way around -- uses the density to do
the conversion.
Vince Calder
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