And click on the Time Machine icon. Click on âSelect Diskâ. Choose your external drive and click on âUse Backup Diskâ. Time Machine will copy everything (OS, Software, Files, and Preferences) to the external hard drive.
The standard enthalpy of formation of a pure element is in its reference form its standard enthalpy formation is zero. Carbon naturally exists as graphite and diamond. The enthalpy difference between graphite and diamond is too large for both to have a standard enthalpy of formation of zero. To determine which form is zero, the more stable form of carbon is chosen. This is also the form with the lowest enthalpy, so graphite has a standard enthalpy of formation equal to zero. Table 1 provides sample values of standard enthalpies of formation of various compounds.
The stable form of carbon is carbon 12 and the radioactive isotope carbon 14 decays over time into carbon 12 and other particles. Carbon is naturally in all living organisms and is replenished in the tissues by eating other organisms or by breathing air that contains carbon.At any particular time all living organisms have approximately the same ratio of carbon 12 to carbon 14 in their tissues.he stable form of carbon is carbon 12 and the radioactive isotope carbon 14 decays over time into carbon 12 and other particles. Carbon is naturally in all living organisms and is replenished in the tissues by eating other organisms or by breathing air that contains carbon.