Terminal alkynes show acidity due to terminal hydrogen atom which can be easily abstracted by a strong base like sodium amide (NaNH₂). Terminal alkynes show acidity compared to other hydrocarbons due to more ‘s’ character of terminal carbon which is sp hybridized. Due to more ‘s’ character, it withdraws the electron of terminal hydrogen attached to it so that it can be easily abstracted in the presence of a strong base and shows acidic character.