Lilpeeq's question is legitimate, but I'm going to try to answer without the statements anyway (potentially ill-advised, but here we go!). Nonmetal-nonmetal bonds are more likely to be covalent because their electronegativites are very similar. Ionic bonds form between elements with large differences in electronegativities, and the smaller the difference is, the more covalent the bond is until an element that bonds with itself forms a perfectly covalent bond. Metals form metallic bonds with each other.
EDIT: Basically they have small differences in electronegativity. Thanks for following up on your question! Hope this helps!
An open system can exchange both energy and matter with its surroundings. The stovetop example would be an open system, because heat and water vapor can be lost to the air.
