Answer:
If the cap is left off, some of the dissolved CO2 can escape as gas from the bottle, making the pop go flat faster (less dissolved CO2 in pop). If the cap is placed tightly, the gaseous CO2 cannot readily escape the bottle thus your pop won't go flat
Explanation:
If the cap is left off, some of the dissolved CO2 can escape as gas from the bottle, making the pop go flat faster. If the cap is placed tightly, the gaseous CO2 cannot readily escape the bottle thus your pop won't go flat.
Just some fun related concept:
A similar concept comes into play for the reason behind why pop tastes better in fridge then just keeping at normal temperature. This is because gases tend to have high solubility at cold temperatures thus CO2 is more readily dissolved in fridge than outside room temperature which is why it tastes great!