Singular noun is a noun that assigns to one thing, one person and one idea. Example: Boy, Girl, Father, Mother, Man, Doctor and so on.
That is a chemical change if your talking about gases
Check what?
I dont think this is my laptop but nothing is applied
Speed is the magnitude of its velocity(the rate of change of its position), it is thus a scalar quantity. Base on that, the possible non example for speed is the acceleration, measurement of the mass, the volume, and any measurement but not speed. I hope you are satisfied with my answer and feel free to ask for more
My answer would be thwack, as in the suction y noise when you step out of the mud.