( ( Understand ( ( ( the ( pH scale ) ) and ) ( ( the definition ) ( of ( ( acid and ) base ) ) ) ) ) . )
(ROOT (S (VP (VB Understand) (NP (NP (DT the) (NN pH) (NN scale)) (CC and) (NP (NP (DT the) (NN definition)) (PP (IN of) (NP (NN acid) (CC and) (NN base)))))) (. .)))
Understand the pH scale and the definition of acid and base.
(ROOT (S (NP (NNS Acids)) (VP (VBP are) (VP (VBN associated) (PP (IN with) (NP (NP (DT a) (JJ low) (NN number)) (PP (IN on) (NP (DT the) (NN ph) (NN scale))))))) (. .)))