Julie's science teacher asked her to use quantitative observation to distinguish between 3 metal cylinders to identify aluminum, brass, and copper. what should she do first? a) use color to identify the metals. b) calculate the density of the samples. c) determine the temperature of the metals. d) measure the malleability of the cylinders.

Since the teacher has said to use quantitative observation, density is the easiest measurement to make. Aluminum has a density of 2.7 g/mL. Brass has a density of 8.73 g/mL. Copper has a density of 8.96 g/mL. As long as the mass and volume measurements are accurate (water displacement can be used for volume measurements), the resulting density values can be distinguished.

It may be possible to distinguish these three metals visually, based on color, but the instructions have stated to use quantitative observation.

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.