Breaking an egg is an example of a physical change. This is because the egg was broken, thus its physical appearance was different. If you were to cook the egg, that would be a chemical change because that would result in a new chemical formation of the stuff inside of the egg. But since you're only breaking the egg, it's just a physical change.
I guess that answers both questions.
Hope that helped!
The periodic table arranges the elements into families and periods (vertical and horizontal rows). The elements in each family have similar properties. As you go across a row, the properties vary gradually from one element to the next. The table tells you what elements may have similar chemical and physical properties.The periodic table describes the atomic structure of all known elements. For instance, by looking at the periodic table, you can find out the atomic mass and the number of electrons the element has. Each element has its own separate set of such data. No two elements are the same.This is perhaps the most useful feature of the Periodic Table. It is an excellent reference tool. In one place, you can find many properties of an element.
-130KJ is the standard heat of formation of CuO.
Explanation:
The standard heat of formation or enthalpy change can be calculated by using the formula:
standard heat of formation of reaction = standard enthalpy of formation of product - sum of enthalpy of product formation
Data given:
Cu2O(s) ---> CuO(s) + Cu(s) ∆H° = 11.3 kJ
2 Cu2O(s) + O2(g) ---> 4 CuO(s) ∆H° = -287.9 kJ
CuO + Cu ⇒ Cu2O (-11.3 KJ) ( Formation of Cu2O)
When 1 mole Cu20 undergoes combustion 1/2 moles of oxygen is consumed.
Cu20 + 1/2 02 ⇒ 2CuO (I/2 of 238.7 KJ) or 119.35 KJ
So standard heat of formation of formation of Cu0 as:
Cu + 1/2 02 ⇒ CuO
putting the values in the equation
ΔHf = ΔH1 + ΔH2 (ΔH1 + ΔH2 enthalapy of reactants)
heat of formation = -11.3 + (-119.35)
= - 130.65kJ
-130.65 KJ is the heat of formation of CuO in the given reaction.
Stored energy is described as potential energy
