What is the difference between a mixture, compound, element and pure substance

mixture = when two or more substances combine without making a new substance.

compound = elements that are bonded together chemically

element = the simplest form of matter that cannot be broken down

pure substance = a substance made up of one compound

basically the differences are their definitions :D

c, liquids evaporate, creating a gas

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.