Density
Alright! Imagine you’ve got a box, and you fill it up with a liquid, like water or ketchup. The density of that liquid is essentially a measure of how much stuff (or mass) is packed into a specific volume of space. So, it’s like asking, “How heavy is the liquid in this box compared to the size of the box?”
To calculate the density, you’d take the mass of the liquid (how much it weighs) and divide it by the volume of the box (how much space it occupies). The formula is:
Now, about those units. In the metric system, mass is typically measured in kilograms (kg) and volume in cubic meters (m³). So, the density would be in kg/m³. In the more everyday scale, you might see grams (g) for mass and milliliters (mL) or cubic centimeters (cm³) for volume, giving a density in g/mL or g/cm³.
However, and here’s the caveat, in most situations, the difference in units is going to matter. Just be sure you aren’t accidentally mixing and matching units! So, always make sure your units are consistent, and you’ll be just fine.
While it’s unlikely you’ll be directly asked to calculate density, this concept often merges with other problems. In tackling density calculations, there are two primary strategies: using dimensional analysis to align your units or directly substituting values into the equation. Practice both methods, but prioritize honing your dimensional analysis skills. This technique is incredibly valuable across various MCAT physics topics
Use the practice set below to further develop these skills.