Can someone explain Specific Gravity?

[PolarisNorth]

http://www.tpub.com/content/engine/14105/css/14105_20.htm
This website tells me that Specific Gravity is
weight of substance/weight of equal volume of water
or
density of substance/density of water.

Can someone explain how this is true? Density and weight are two different things so how do they both give me SG?

Please help me! I am very confused.

 

[Doc Al]

Can someone explain how this is true? Density and weight are two different things so how do they both give me SG?

As long as you use equal volumes, the ratio of weights will equal the ratio of densities.

Let V stand for volume; d for density; w for weight. Then the ratio of weights will equal:

w₁/w₂ = (d₁Vg)/(d₂Vg) = d₁/d₂.

 

[Dadface]

SG=density of substance/density of water
density=mass/volume,therefore:
SG=(mass/volume of substance)/(mass/volume of water)...if volumes are equal:
SG=mass of substance/mass of equal volume of water...Weight=Mg therefore:
SG=(Weight of substance/g)/(weight of equal volume of water/g) If the weighings are carried out at the same place g would be constant and cancels out..therefore:
SG=weight of substance/weight of equal volume of water.

You beat me again Doc Al

 

[PolarisNorth]

Broken down and written out, that would be:
Weight = (Density)(Volume)(Force of Gravity)
Weight = (Mass/Volume)(Volume)(Force of Gravity)
Weight = (Mass)(Force of Gravity)

Is this where w1=d1Vg and w2=d2Vg comes from?
I think this makes sense now. Thank you very much! I really appreciate it.

Edit: Nevermind. No need to answer this. Dadface answered it for me.

 

[pmacias]

Sure, I'd be happy to explain Specific Gravity to you. Specific Gravity is a measurement that compares the density of a substance to the density of water. Density is a measure of how much mass is contained within a certain volume. Weight, on the other hand, is a measure of the force of gravity on an object. While they may seem like two different things, they are actually related because the weight of an object is affected by its density. This is why Specific Gravity can be calculated using either weight or density.

To understand this better, let's look at an example. Imagine you have two objects that are the same size, one made of lead and one made of aluminum. The lead object will have a greater weight because it has a higher density (more mass in the same volume), whereas the aluminum object will have a lower weight because it has a lower density (less mass in the same volume).

Now, let's apply this to Specific Gravity. When we calculate Specific Gravity, we are comparing the density of a substance to the density of water. Water is often used as a reference because it has a density of 1 g/mL. This means that if we take the weight of a substance and divide it by the weight of an equal volume of water, the result will be the Specific Gravity of that substance. Similarly, if we take the density of a substance and divide it by the density of water, the result will also be the Specific Gravity.

In summary, Specific Gravity is a measure of how dense a substance is compared to water. It can be calculated using either weight or density because these two factors are related. I hope this helps to clarify any confusion you may have had.