What is ph value ? what is the ph value of water

It measures the concentration of H+ ions OH- ions. ph value of water is 7.

pH is essentially a measure of the concentration of Hydrogen (H) ions in a solution. This is where the confusing part comes in. The higher the concentration of H ions there are, the lower the pH. This means that the solution is more "acidic."
pOH is a measure of the concentration of Hydroxy ions in a solution. The higher the concentration, the higher the pH a and the lower the pOH. This makes the solution more "basic."

The pH scale ranges from 0 - 14, where as implied above, the lower the value the more acidic the solution is because it is more concentrated with H ions.

Water has a pH/pOH of 7 because it is considered to be a neutral solution. There is an even about of H ions and OH ions in the solution. Its pH can be altered with the addition of an acidic solution or basic solution because you are essentially adding in more ions.

pH measures whether something is acidic or alkaline, it ranges from 0-14 with 0 being very acidic and 14 being very alkaline. Water would be rated at 7 because it is 'neutral' (neither acidic nor alkaline). You can test something's pH level with 'Universal indicator paper' (paper that you dip into a liquid) or 'Universal indicator solution', (a solution that changes colour depending on whether something is acidic or alkaline). Acids will turn the paper/solution red and alkalis will turn it blue.

Hope this helped!

pH value gives you a brief idea whether a substance is acidic or a substance is alkaline.

acidic would mean you would have more protons(H+) and would vary between 1 to 7 on the pH scale.

Alkaline would mean you would have more hydroxide ions(OH-) and would vary between 7 to 14 on the pH scale.

Now water(H2O) would dissociate at 25 degree Celsius to give you H+ and OH-.