Expansion of Liquid
- In case of liquid linear and superficial expansivities are absent.
- Liquid is heated in a vessel which expand itself so the expansion that we observe is called apparent expansion.
- Apparent expansion is always less than real or absolute expansion due to expansion of vessel.
- Coefficient of apparent expansion or apparent expansivity ()
- The apparent change in volume per unit original volume per degree change in temperature is called apparent expansivity.
- or =
- Coefficient of real expansion or real expansivity ()
- Real change in volume per unit original volume per degree change in temperature is called real expansivity. It is constant for a liquid.
- or =
Real expansion = Apparent expansion + Expansion of vessel.
Where, =Cubical expansivity of vessel.
- A vessel completely filled by liquid is heated then volume of liquid overflow or on cooling volume of empty space above liquid is
- A liquid is placed in a vessel upon certain mark so that level of liquid remain at same mark at all temperature then,
- Liquid is placed in a vessel so that volume of empty space above liquid remain same at all temperature then,
Change in density
- When temperature is increased, the volume of the constant mass also increase and hence the density decrease.
Dulong and Petit's Experiment
- When and be the height of liquid column in two sides of U shaped tube at and then,
Absolute expansivity () =
- The height - is measured with a cathetometer or a travelling microscope mounted vertically.
- This experiment is done to find the real expansivity of the liquid.
Correction of Barometer
- When the height of barometer is observed at then true height is given by
, Where is linear expansivity of scale.
- The correct height is measured at , then reading at is observed then
Anomalous Behavior of Water
- It is a different behavior of water where water expands on cooling from to and vice versa.
- Water has greatest density and least volume at
- Water freezes from top of pond, which is an example of Anomalous Behavior. Existence of aquatic life on ice age was possible due to this behavior too.
- Expansivity of water is -ve from to .
- Mean or average expansivity of water is 0 at .
Expansion of Gas
For expansion of gas, study the topic "Gas Laws".