Type of chocolate bar, size of it, surface it is placed on, etc
Controlled variables are anything that stay the same for both trials
What determines the chemical properties is : color, hardness, luster, crystal forms, density, and cleavage.
This is the era of recent life that began about 66 million years ago and continues today. It includes the first appearance and Homo sapiens about 400,000 years ago. <span />
