# Direct and inverse relationship formula for volume

### Direct and Inverse Variation - My Math Forum

Apr 17, This has the mathematical formula of y = kx, where k is a constant. When there is a direct or inverse relationship, x and y are proportional to. Apr 25, A direct proportion occurs when you have a direct relationship between one In this equation, you can also see that volume has an inverse. density = mass/volume volume = mass/density clearly volume and mass are directly proportional, as you see in the second equation. (just applied the simple .

This relationship between the two quantities is described as follows: Dividing both sides of Equation 6. The numerical value of the constant depends on the amount of gas used in the experiment and on the temperature at which the experiments are carried out. At constant temperature, the volume of a fixed amount of a gas is inversely proportional to its pressure. Boyle used non-SI units to measure the volume in. Hg rather than mmHg. Because PV is a constant, decreasing the pressure by a factor of two results in a twofold increase in volume and vice versa.

The Relationship between Temperature and Volume: Charles's Law Hot air rises, which is why hot-air balloons ascend through the atmosphere and why warm air collects near the ceiling and cooler air collects at ground level. Because of this behavior, heating registers are placed on or near the floor, and vents for air-conditioning are placed on or near the ceiling.

The fundamental reason for this behavior is that gases expand when they are heated. Because the same amount of substance now occupies a greater volume, hot air is less dense than cold air. The substance with the lower density—in this case hot air—rises through the substance with the higher density, the cooler air.

A sample of gas cannot really have a volume of zero because any sample of matter must have some volume. Note from part a in Figure 6. Similarly, as shown in part b in Figure 6. The Relationship between Volume and Temperature. The temperature scale is given in both degrees Celsius and kelvins.

### A sense of proportion | Maths | Education in Chemistry

The significance of the invariant T intercept in plots of V versus T was recognized in by the British physicist William Thomson —later named Lord Kelvin. At constant pressure, the volume of a fixed amount of gas is directly proportional to its absolute temperature in kelvins. This relationship, illustrated in part b in Figure 6. We didn't even write it.

We could write y is equal to 1x, then k is 1. We could write y is equal to 2x. We could write y is equal to negative 2x. We are still varying directly.

We could have y is equal to pi times x. We could have y is equal to negative pi times x. I don't want to beat a dead horse now. I think you get the point. Any constant times x-- we are varying directly.

And to understand this maybe a little bit more tangibly, let's think about what happens. And let's pick one of these scenarios. Well, I'll take a positive version and a negative version, just because it might not be completely intuitive. So let's take the version of y is equal to 2x, and let's explore why we say they vary directly with each other. So let's pick a couple of values for x and see what the resulting y value would have to be.

So if x is equal to 1, then y is 2 times 1, or is 2. If x is equal to 2, then y is 2 times 2, which is going to be equal to 4. So when we doubled x, when we went from 1 to so we doubled x-- the same thing happened to y.

So that's what it means when something varies directly. If we scale x up by a certain amount, we're going to scale up y by the same amount.

If we scale down x by some amount, we would scale down y by the same amount. And just to show you it works with all of these, let's try the situation with y is equal to negative 2x. I'll do it in magenta. Let's try y is equal to negative 3x.

So once again, let me do my x and my y. When x is equal to 1, y is equal to negative 3 times 1, which is negative 3.

When x is equal to 2, so negative 3 times 2 is negative 6. So notice, we multiplied. So if we scaled-- let me do that in that same green color. If we scale up x by it's a different green color, but it serves the purpose-- we're also scaling up y by 2.

## Ways to give question about direct and inverse proportion

To go from 1 to 2, you multiply it by 2. To go from negative 3 to negative 6, you're also multiplying by 2. So we grew by the same scaling factor. To go from negative 3 to negative 1, we also divide by 3. We also scale down by a factor of 3.

So whatever direction you scale x in, you're going to have the same scaling direction as y. That's what it means to vary directly. Now, it's not always so clear. Sometimes it will be obfuscated. So let's take this example right over here. And I'm saving this real estate for inverse variation in a second. You could write it like this, or you could algebraically manipulate it. Or maybe you divide both sides by x, and then you divide both sides by y.

These three statements, these three equations, are all saying the same thing. So sometimes the direct variation isn't quite in your face.

But if you do this, what I did right here with any of these, you will get the exact same result. Or you could just try to manipulate it back to this form over here. And there's other ways we could do it. We could divide both sides of this equation by negative 3. And now, this is kind of an interesting case here because here, this is x varies directly with y. Or we could say x is equal to some k times y. And in general, that's true.

If y varies directly with x, then we can also say that x varies directly with y. It's not going to be the same constant.