V1/T1 = V2/T2. [ as P = const.]
400/300=V2/288
V2 = 384
thus change = 16 ml

Given:
Initial volume of oxygen (Vi) = 400 ml
Initial temperature (Ti) = 27°C
Final temperature (Tf) = 15°C
Pressure remains constant

To find:
Contraction in volume of oxygen

Formula:
Charles' Law states that the volume of a gas is directly proportional to its temperature, given that the pressure and amount of gas remain constant. Mathematically, it can be represented as:
V1/T1 = V2/T2

where:
V1 = Initial volume
T1 = Initial temperature
V2 = Final volume
T2 = Final temperature

Solution:
We can use Charles' Law to find the final volume of oxygen.

Step 1:
Convert the temperatures from Celsius to Kelvin.
Ti = 27°C + 273.15 = 300.15 K
Tf = 15°C + 273.15 = 288.15 K

Step 2:
Substitute the values into the Charles' Law formula:
Vi/Ti = V2/Tf

Step 3:
Rearrange the formula to solve for V2:
V2 = (Vi * Tf) / Ti

Step 4:
Substitute the given values into the formula:
V2 = (400 ml * 288.15 K) / 300.15 K

Step 5:
Calculate the contraction in volume:
V2 = 385.25 ml

Therefore, the contraction in volume of the oxygen is 400 ml - 385.25 ml = 14.75 ml.

Explanation:
When a gas is cooled, its particles lose kinetic energy, resulting in decreased movement and a decrease in volume. Charles' Law helps us understand this relationship between temperature and volume. By using the formula and substituting the given values, we can calculate the final volume of the oxygen after cooling.

The initial volume of the oxygen is 400 ml, and its initial temperature is 27°C. The final temperature after cooling is 15°C. We convert the temperatures to Kelvin, as temperature must be in Kelvin for calculations involving gas laws.

Using Charles' Law, we can find the final volume of the oxygen. By rearranging the formula and substituting the values, we calculate that the final volume is 385.25 ml. Therefore, the contraction in volume is 14.75 ml (400 ml - 385.25 ml).

This contraction in volume occurs because the decrease in temperature causes the oxygen gas particles to slow down and occupy less space.