In this experiment, the independent variable is the surface, the dependant variable is the distance one end of the surface must be lifted to see movement of the object, and the control variable is the object. Since the surface height at one end is changed and the object is kept the same, the only conclusion that can be made is whether the surface has an effect on the force of friction. Of course, basic physics tells you that it does, therefore A is correct.
A reaction that releases heat is known as an exothermic reaction.
Reactions can be classified as either exothermic or endothermic depending on whether they release or absorb heat from the surrounding.
A reaction that absorbs or gains heat from the surrounding is known as endothermic reaction.
On the other hand, if a reaction releases heat to the surrounding is known as exothermic reaction.
An exothermic reactions results to an increase in temperature of a solution while an endothermic reaction results to a decrease in the temperature of a solution.
