A doctor wants to test a new medicine that will help people who have trouble sleeping. He has two groups of volunteers. He plans to give the medicine to group I and not to group II. Group II will be the control group. The doctor knows that people taking the medicine may sleep better just because they expect the medicine to work. How can he be sure of whether the medicine really works?

explanation: it gains negative electrons, therefore becoming negatively charged. as charge cannot be created, nor destroyed, only transferred, this leaves the wool positive. now that they have opposite charges, the two items attract.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.