Tin pest related problems such as tin whiskers. At 13.2 °C (about 56 °F) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form "white tin" to the brittle, nonmetallic, α-form "grey tin" with a diamond cubic structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures of roughly −30 °C aids the initiation. There is also a large volume increase of about 27% associated with the phase change to the nonmetallic low temperature allotrope. This frequently makes tin
Gift Gift A gift or a present is an item given to someone without the expectation of payment or anything in return. An item is not a gift if that item is already owned by the one to whom it is given. Although gift-giving might involve an expectation of reciprocity, a gift is meant to be free. In many countries, the act of mutually exchanging money, goods, etc. may sustain social relations and contribute to social cohesion. Economists have elaborated the economics of gift-giving into the notion of a gift economy. By extension the term "gift" can refer to any item