To measure the volume of a regular shaped rock, simply fill up a container with volume markings to a desired quantity of water. Record this quantity. Then place the rock in the water. Record the new volume. Find the difference between the new volume and the old volume and you will have the volume of your regular shaped rock.
You would determine the volume of water it displaces and measure it.
You could weigh it. You can also determine its density by comparing it to an equal volume of water, but first you would have to determine how much water it displaces to determine its volume.
To calculate density, you need to divide the mass of the rock by its volume. In this case, the density of the rock would be 12g divided by its volume in cm^3. Without knowing the volume in cm^3, it is not possible to determine the density of the rock.
Not always easy. Since density is defined as the mass of a unit volume of material,you would measure the volume of the rock by putting it into a container half filled with water and then measure the volume change.
A measuring jug is all you need for the volume and a mass balance is needed to determine mass.
Determine its volume by how much water it displaces, then divide mass by volume
If you want to determine the density of an object, you would measure the mass and volume, then divide mass/volume to determine density. This can help determine the composition of the object. For example, if you find a rock that looks like a gold nugget. The density of gold is a known value, so one of the tests in determining if you are holding real gold would be to determine the density of your rock. This is one example. Another (maybe more 'real world' for you). Shipping and cargo companies measure the volume of packages as they go by on the conveyor belt, so that they can figure how many will fit in a particular truck.
A scale can measure the weight of a rock, but it does not directly measure its volume. To determine the volume, you can use methods like water displacement or geometric calculations if the rock’s shape is regular. The relationship between weight and volume can then be used alongside the rock's density if needed.
Fill a graduated cylinder full of water, than drop a rock inside. The amount that the water rises will determine the volume of the rock. Amount of water level increase=volume of rock.
To determine the density of an object, you need its mass and volume. If the object is oddly shaped, you can determine its volume by measuring the volume of water displaced when thee object is submerged in a container of water.
I would assume that you would use displacement to determine volume when the object is extremely complicatedly shaped.
You would first determine the mass of the egg. Then you would need to determine the volume of the egg through water displacement. Then you would need to divide its mass by its volume, and that will give you the density.