Because freezing will often burst the cell walls and destroy tissue. The crystals of ice are very sharp and hard to control AFAIK. Note what happens to a banana or many types of fruit after you dethaw — it becomes all mushy and not of the same structure, fiber and cell form as before, like a bad beam up in Star Trek.
Plant cells have walls that arent very flexible, so a plate forms in between the cells, and the cell splits in half.
Your nose and your mouth are both a portal of entry into your body. If you cover one and not the other it defeats the purpose because Bacteria can still enter the system. They are both part of your respiratory system.
Radiation is the transfer of heat energy through space by electromagnetic radiation. Most of the electromagnetic radiation that comes to earth from the sun is in the form of visible light. Light is made of waves of different frequencies.
Hope this helps :)
There are 4 outer atoms and lone pairs that are present in a molecule with a see-saw shape. It was called "seesaw" comes from the observation that it looks like a playground seesaw. It is very common that four bonds to a central atom result in tetrahedral or, less commonly, square planar geometry.
