Chemical because the propane has stored chemical energy which is being released and a by-product of that propane is heat or themal energy.
Any buffer exists in this equilibrium
HA <=>

In a buffer, there is a large reservoir of both the undissociated acid (HA) and its conjugate base (

)
When a strong acid is added, it reacts with the large reservoir of the conjugate base (

) forming a salt and water. Since this large reservoir of the conjugate base is used, the ph does not alter drastically, but instead resist the pH change.
Answer:
The elements in the reactants are the same as the elements in the products.
Explanation:
You can't have more or less elements or atoms, but you also can't just have the same number of atoms because then it could be different elements, which can't happen.
Answer:
All the option are correct
Explanation:
The ocean currents have been associated with past climatic shifts during critical periods (for example, the ice ages), where modifications in water circulation might have caused important climatic changes.
From a biological point of view, the ocean currents may be associated not only with the climate but also biogeochemical cycles through modifications in the distribution of heat and freshwater. Thus, the changes in ocean circulation may produce biogeographical shifts by affecting the local climate. The importance of ocean currents in affecting biodiversity is also represented by the equilibrium of coral reef ecosystems, where this equilibrium is broken up by factors such as transport of pollutants, temperature conditions, etc., which are known to alter thermosensitive coral species.