What is the effect of impurities on the melting point of a compound

Is this a single replacement reaction or there is no

Substance x has a fixed volume, and the attraction between its particles is strong .substance y had widely spread out particles and can be compressed what can most likely be concluded about these substances

Why does the sun appear to be the brightest star in the sky? a- its apparent brightness is much greater than other stars. b- it burns more gas, making it brighter than any other star. c- it is the largest star in the galaxy, so it is the brightest star. d- its relative distance to earth is closer than the other stars.