Acompound (c4h6o2) has a strong band in the infrared at 1760 cm^-1. its 13c nmr spectrum exhibits signals at 8 20.2 (ch3), 96.8 (ch2), 141.8 (ca), and 167.6 (c). the 1h nmr spectrum of the compound has a three-proton singlet at δ 2.1 along with three other signals, each of which is a doublet of doublets, at 8 4.7, 4.9, and 7.3. what is the structure of the compound?

Two metal blocks that have slightly different temperatures are placed next to one another. after five minutes, they both have lower but equal temperatures. according to the law of conservation of energy, what  most likelyhappened? energy was created inside the blocks. energy was destroyed inside the blocks. energy was absorbed into the blocks from outside the system. energy was transferred from the warmer block to the cooler block.

The identities of substances are the same before and after which type of change

This statement about matter and its behavior is best classified as a