Question

which is an example of making a quantitative observation? measuring the mass of metal used in a reaction recording the color of a solid formed in a reaction describing a liquid as having a slippery feel telling an odor on how nice it smells

Explanation:

A quantitative observation involves measuring or counting (using numbers). Measuring the mass of metal (a numerical value) is quantitative. The other options (color, slippery feel, smell) are qualitative (descriptive, non - numerical).

Answer:

A. measuring the mass of metal used in a reaction