How could you draw a model of the element copper to show that it is different from the element gold?

This is a mixture that has the same composition throughout.

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt

What is the value of the standard enthalpy of formation of an element in its most stable form?