Question

which of these is a property of acids?
they turn litmus paper blue.
they feel slippery.
they taste bitter.
they produce hydrogen gas when reacted with metals.

Explanation:

Acids react with metals to produce hydrogen gas. For example, when zinc reacts with hydrochloric acid, the reaction is \(Zn + 2HCl=ZnCl_{2}+H_{2}\uparrow\). Litmus paper turns red in acid (not blue). Bases feel slippery and taste bitter, while acids have a sour taste.

Answer:

They produce hydrogen gas when reacted with metals.