Wayne Piemmons, age 13, of Asheville, N.C., For his question:

Why does melting snow lose its white colors?

Snow is a frothy mixture of ice crystals and pockets of air. The arrangement of its molecules does not absorb any of the wavelengths of light, and they are bounced back to our eyes as white. As the snow melts, the arrangement of its molecules changes. The pockets of air escape, and the icy fragments turn to water.

This different arrangement plays different tricks with the light. The melting water becomes transparent, letting the rays of light pass right through it. It appears murky because it is tinged with the muddy ground below it. Also, the melted snow may be grimy with dust and dirt that was trapped among the snowflakes.