Like solid, liquid expands on heating and contracts on
cooling, because liquid is always held in a container, the expansion of liquid
is always complicated because of the expansion of the container itself.

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Related:

- Principles of Expansion
- Cubic Expansivity
- Linear Expansivity
- Thermal expansivity
- Area Expansivity
- Unusual Expansion
- Anomalous expansion of water

**Real and apparent expansivity**

Since the expansion of liquid is complicated because of the
expansion of the container, it is therefore necessary to distinguish between
the real and apparent cubic expansivity of liquid.

*=*

**Real expansion***Apparent expansion*+

*Expansion of the container*

**Real cubic expansivity**

The real (or absolute) cubic expansivity of a liquid can be
denoted by “

**ɣr”**, it is the**absolute**increase in volume, per unit volume, per degree rise in temperature.**Apparent Cubic expansivity**

The apparent cubic expansivity of a liquid can be denoted by
“

**ɣa”**, it is the increase is volume, per unit volume, per degree rise in temperature, when the liquid is heated in an expansible vessel.The apparent cubic expansivity “

**ɣa”**depends also on the cubic expansivity “

**ɣ”**. Therefore, the real expansivity of liquid “

**ɣr”**is always more than the apparent expansivity of liquid “

**ɣa”**, it can be shown that the difference between the rel an apparent expansivity of a liquid is the cubic expansivity of the vessel.

Therefore,

**ɣr = ɣa + ɣ**

**FORMULAR**

**ɣr = ɣa + ɣ**

Apparent expansivity can be calculated given the mass liquid
expelled over mass of the liquid remaining, multiplied by the temperature rise.

Let,

m = Mass

e = density

V = volume

ɣa = Apparent cubic expansivity

θ = Change in temperature

Therefore,

ɣa = (m1 -m2) / m2(θ1- θ2)

**An Example**

A density bottle holds 250 of
liquid at 30°C
and only 248.5 at 60°C, find;

a) the apparent expansivity

b) the real expansivity

Given linear expansivity = 0.000006
per kelvin.

**Solution**
ɣa = (m1 -m2) / m2(θ1- θ2)

ɣa = (250 -248.5) / 248.5(60- 30)

ɣa = 0.000201207

Cubic expansivity = 3*Linear
expansivity

ɣ = 3*(0.000006) = 0.000018 per kelvin

**ɣr = ɣa + ɣ**

**ɣr =**(0.0002 + 0.000018) = 0.0002192 per k

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