“稀硝酸溶液”的英语词汇是______（）
A. a weak solution of nitric acid
B. free oxygen
C. by-product
D. the amount of proteins
Which of the following processes would you classify as chemical reactions（）
A. The burning of paper
B. The formation of rust on iron
C. The boiling of water
D. The preparation of sugar syrup by adding sugar to hot water
E. The manufacture of salt by evaporation of sea water
Which of the following properties can be classified as the physical properties of a substance（）
A. hardness
B. density
C. solubility
D. ductility
E. malleability
F. melting point
G. boiling point
H. crystalline form
I. mass
J:volume
“游离氧”的英语词汇是______（）
A. free oxygen
B. nitrogen fixation
C. by-product
D. the amount of proteins
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