Specific gravity

Get a jar. Add a handful of gold nuggets, 1 cup of cooking oil, and fill it up

with water. Put a lid on it, shake briskly, and let sit for 37 seconds. Record

what happens. Shake it up and try again. Did you get the same response? Why does

the gold always settle to the bottom and the oil float to the top? To understand

we have to look inside matter and see how it is put together.

Imagine one (1) cubic centimeter of water: if pure and at "standard temperature

and pressure" it will have a mass of one (1) gram. The size (1 cm3) is a volume

and represents "how big." The mass represents "how much."

Now imagine a cubic centimeter of pure gold, which has a mass of 19.3 grams.

The "how big" is the same, but the "how much" has increased by almost 20 times.

What about the oil? A cubic centimeter actually has a mass less than 1 gram.

For oil, the "how much" is less. Why aren't all 3 substances the same? Clearly

there is another factor involved here which relates to "how tightly is it packed

at the atomic level?"

We call this new factor "density." Density is calculated by dividing the

"how much" by the "how big," and is expressed in grams per cubic centimeter.

How tightly packed = how much / how big

or

Density = Mass / Volume

Specific gravity is the density of a substance divided by the density of water.

Since water has a density of 1 gram/cm3, and since all of the units cancel,

specific gravity is the same number as density but without any units.

Get a jar. Add a handful of gold nuggets, 1 cup of cooking oil, and fill it up

with water. Put a lid on it, shake briskly, and let sit for 37 seconds. Record

what happens. Shake it up and try again. Did you get the same response? Why does

the gold always settle to the bottom and the oil float to the top? To understand

we have to look inside matter and see how it is put together.

Imagine one (1) cubic centimeter of water: if pure and at "standard temperature

and pressure" it will have a mass of one (1) gram. The size (1 cm3) is a volume

and represents "how big." The mass represents "how much."

Now imagine a cubic centimeter of pure gold, which has a mass of 19.3 grams.

The "how big" is the same, but the "how much" has increased by almost 20 times.

What about the oil? A cubic centimeter actually has a mass less than 1 gram.

For oil, the "how much" is less. Why aren't all 3 substances the same? Clearly

there is another factor involved here which relates to "how tightly is it packed

at the atomic level?"

We call this new factor "density." Density is calculated by dividing the

"how much" by the "how big," and is expressed in grams per cubic centimeter.

How tightly packed = how much / how big

or

Density = Mass / Volume

Specific gravity is the density of a substance divided by the density of water.

Since water has a density of 1 gram/cm3, and since all of the units cancel,

specific gravity is the same number as density but without any units.