Four liters of gas at standard pressure is compressed into 0.85 l gas cylinder. what is the new pressure

              4.70 atm

Solution:
               According to Boyle's Law, " The Volume of a given mass of gas at constant temperature is inversely proportinal to the applied Pressure". Mathmatically the initial and final states of gas are given as,

                                      P₁ V₁  =  P₂ V₂    (1)

Data Given;
                   P₁  =  1 atm (standard pressure)

                   V₁  =  4 L

                   P₂  =  ??

                   V₂  =  0.85 L

Solving equation 1 for P₂,

                    P₂  =  P₁ V₁ / V₂

Putting values,

                    P₂  =  (1 atm × 4 L) ÷ 0.85 L

                    P₂  =  4.70 atm

Result:
           As the volume has decreased from 4 L to 0.85 L, therefore, pressure got increased from 1 atm to 4.70 atm.

What? i don’t understand

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water