Orange

Why do oranges float when not peeled and sink when peeled?

The unpeeled orange floats because the rind is very porous and filled with tiny pockets of air. Even though you're removing mass when you peel the orange, the peeled orange is more dense and sinks in the water.

Burette

Burette

A burette is a vertical cylindrical piece of laboratory glassware with a volumetric graduation on its full length and a precision tap, or stopcock, on the bottom. It is used to dispense known amounts of a liquid reagent in experiments for which such precision is necessary, such as a titration experiment(a common laboratory method of quantitive chemical analysis that is used to determine the unknown concentration of a known reactant).Burettes measure from the top since they are used to measure liquids dispensed out the bottom. The difference between starting and final volume is the amount dispensed