Here's why:
* The goal of the experiment: To demonstrate the relationship between the density of a solution and the buoyancy of an object (the egg).
* Independent variable: The variable you change is the density of the solution, usually by adding more salt.
* Dependent variable: What you measure is whether the egg floats or sinks.
* Controlled variable: You want to make sure that the only thing affecting whether the egg floats is the density of the solution. This means you need to use the same type of egg throughout the experiment. Different types of eggs have slightly different densities, which could skew your results.
Example:
Imagine you're testing the effect of salt water on egg buoyancy. You use a fresh egg, an old egg, and a hard-boiled egg. The difference in density between these eggs could influence whether they float or sink, even if the salt concentration is the same. To ensure a fair test, you should use only one type of egg.
