<P> Beyond the constraints of closed systems, open systems can gain or lose energy in association with matter transfer (both of these process are illustrated by fueling an auto, a system which gains in energy thereby, without addition of either work or heat). Denoting this energy by E (\ displaystyle E), one may write </P> <Dl> <Dd> <Table> <Tr> <Td> <P> Δ E = W + Q + E . (\ displaystyle \ Delta () E = W + Q + E .) </P> </Td> <Td> <Table> <Tr> <Td> <P> </P> </Td> <Td> <P> </P> </Td> <Td> <P> </P> </Td> </Tr> <Tr> <Td> <P> </P> </Td> </Tr> </Table> </Td> <Td> <P> (3) </P> </Td> </Tr> </Table> </Dd> </Dl> <Dd> <Table> <Tr> <Td> <P> Δ E = W + Q + E . (\ displaystyle \ Delta () E = W + Q + E .) </P> </Td> <Td> <Table> <Tr> <Td> <P> </P> </Td> <Td> <P> </P> </Td> <Td> <P> </P> </Td> </Tr> <Tr> <Td> <P> </P> </Td> </Tr> </Table> </Td> <Td> <P> (3) </P> </Td> </Tr> </Table> </Dd> <Table> <Tr> <Td> <P> Δ E = W + Q + E . (\ displaystyle \ Delta () E = W + Q + E .) </P> </Td> <Td> <Table> <Tr> <Td> <P> </P> </Td> <Td> <P> </P> </Td> <Td> <P> </P> </Td> </Tr> <Tr> <Td> <P> </P> </Td> </Tr> </Table> </Td> <Td> <P> (3) </P> </Td> </Tr> </Table>

What indicates that energy has been added to or removed as he or work from a system