# Would the density and radius of your metal appear to be higher or lower if you forgot to tap the flask to release air bubbles?

For this lab we had to measure out copper in flasks, but tap them out before so no air bubbles would affect the weight. We have this question at the end of the lab and so I wasn't sure if the density/radius would be higher or lower if I didn't tap them out and why.

We were trying to figure out the size on an atom of copper. To find the density of the sample, we had to add about 1/3 of copper to an empty flask and weigh it with the metal. Then after we had to add enough water to just cover the metal, then gently tap and rotate the volumetric flask to remove any air bubbles. Then fill to the calibration mark with water and reweigh the volumetric flask containing the water solid mixture.

• In short, you were measuring the mass and volume of copper. Which of these measurements would be affected by the air bubbles, and how? – Ivan Neretin Sep 14 '15 at 21:02
• Yes. We are trying to figure out if those and density would be higher or lower based on if I hadn't tapped out the bubbles. – Zoe Sep 14 '15 at 21:04

The volume occupied by your copper sample was determined by measuring how much water the copper displaced. So, if the volume of water increased by 10 $\mathrm{cm^3}$, then you knew your volume of copper was $\mathrm{cm^3}$. But air bubbles occupy space also. If, for example, 1 $\mathrm{cm^3}$ of the total displaced volume were actually due to air bubbles, then you would actually only have 9 $\mathrm{cm^3}$ of copper, but you would mistakenly have used a value of 10 $\mathrm{cm^3}$.