A(n) ____________ is a substance that cannot be separated into simpler substances by chemical means.
A: mixtures
B: elements
C: atom
D: molecule
A: mixtures
B: elements
C: atom
D: molecule
举一反三
- A chemical is any aspect of a substance which is only seen by means of a chemical reaction (反应).
- To _____ a substance means to produce it by means of chemical or biological reactions. ( ) A: synthesize B: detach C: affix D: attach
- The atomic weight of an atom, or the molecular weight of a molecule, is its mass relative to that of a(n) ________ atom. This is essentially equal to the number of protons plus neutrons that the atom or molecule contains.
- A chemical _______ is any aspect of a substance which is only seen by means of a chemical reaction (反应). A: queries B: property C: obstacles D: margins
- Choose the correct words or phrases to complete the sentences. An element is a substance, the property ____ cannot be changed by any physical means.