( ( Such ( covalent substances ) ) ( ( are ( ( ( ( ( low-boiling-temperature liquids ) ( -LRB- ( ( such ( as ethanol ) ) -RRB- ) ) ) , ) and ) ( ( low-melting-temperature solids ) ( -LRB- ( ( such ( as ( ( iodine and ) ( solid CO2 ) ) ) ) -RRB- ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Such) (NN covalent) (NNS substances)) (VP (VBP are) (NP (NP (NP (JJ low-boiling-temperature) (NNS liquids)) (PRN (-LRB- -LRB-) (PP (JJ such) (IN as) (NP (NN ethanol))) (-RRB- -RRB-))) (, ,) (CC and) (NP (NP (JJ low-melting-temperature) (NNS solids)) (PRN (-LRB- -LRB-) (PP (JJ such) (IN as) (NP (NP (NN iodine)) (CC and) (NP (JJ solid) (NN CO2)))) (-RRB- -RRB-))))) (. .)))
Such covalent substances are low-boiling-temperature liquids (such as ethanol), and low-melting-temperature solids (such as iodine and solid CO2).
(ROOT (S (NP (NNS Gases) (CC and) (NNS liquids)) (VP (VBP become) (NP (NNS solids)) (PP (IN at) (NP (JJ low) (NNS temperatures)))) (. .)))
Gases and liquids become solids at low temperatures.