What type of substance contains more than one kind of element joined by chemical bonds?

The answer is compound.  Elements are composed of one kind of atoms bonded together. There are different types of compounds: ionic, complexes, molecular, and intermetallic compounds. The proportion of elements in the compound is expressed using a chemical formula. An example of an element is Aluminium while an example of a compound is H2S (Hydrogen sulfide).

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).