Scientific theories are always (a. testable b. true c. unreliable). a theory may be changed as a result of (a. competing theories b. new observations c. untested hypotheses) complete the sentences with those options.

1. A. testable

2.new observations

Explanation:

A scientific theory is the one which explains the cause of a natural phenomena through observatory and experimentation approach. It is valid, accurate and acceptable worldwide.

1. It is testable by implementation of suitable methodology for the purpose of proving the cause of the natural phenomena occurring in nature.

2. A the explanation of the theory can be changes on the basis of the new observations obtained after implementation of new technology and methodology.

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.

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