Question: Do 2 objects that are same size and shape have the same mass? Both objects are the same size and both are solid with no hollow spots Objects clearly have different mass. Not only can you feel it if you hold both in your hand but putting both on a scale shows the obvious difference How can 2 objects, which are exactly the same size & shape, have different mass? The difference in mass must have something to do with the atoms in each object

3 possible explanations…. 1.) Steel atoms might have more mass than aluminum atoms 2.) Steel atoms might be smaller so more can fit in the same volume 3.) Steel and Aluminum atoms might be rearranged differently so more steel atoms fit in the same size Any one of these explanations alone, or 2 or 3 together, could be the reason why the steel object has more mass

Copper atoms are slightly smaller than aluminum atoms This means more copper atoms can fit in the same amount of space Though they are smaller, individual copper atoms have more mass than individual aluminum atoms The combination of more atoms, each with greater mass, makes a copper cube weigh more than an aluminum cube of the same size & shape

Density The mass of an object compared to its volume 𝐷𝑒𝑛𝑠𝑖𝑡𝑦= 𝑚𝑎𝑠𝑠 (𝑔) 𝑣𝑜𝑙𝑢𝑚𝑒 (𝑐 𝑚 3 ) Each substance has its own characteristic density because of the size, mass, and arrangement of its atoms or molecules Archimedes gold crown story

Density Need to know 2 things: Mass Volume Mass: Simple to find—just place it on a scale! Scale will give you its mass in grams Volume: Finding the volume of something like a cube is easy Length (cm) x width (cm) x height (cm) = volume (cm3)