This flask originally held some copper wire and a clear solution of nitric acid. the two substances reacted and produced a brown gas and a blue solution. this reaction cannot be reversed. evidence of a chemical reaction is shown by a) ice forming. b) steam rising. c) the formation of a gas. d) a change in state from a solid to a liquid.

The correct answer is option (C).

Explanation:

Evidence which tells us that chemical reaction has occurred:

When the copper wire is held in clear solution of nitric acid brown colored gas was released with change in color of the solution. Both these observations means that chemical reaction has been taken place.

According to the option enlisted the correct answer is option (C).

measuring things 1 litre of water

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.