Both slicing an apple and a chemical change such as cooking and i cannot be reversed. however why is slicing a apple still considered only a physical change

Slicing of an apple is a physical change

Explanation:

Reason being that, when you slice an apple, it is still that same apple, the only thing you will notice is the change is its size as compared to how it was initially. The apple will still be apple because it has not changed to any other form. When you fried an egg, the egg will undergo some combustion reactions and combustion reaction is a chemical Change and looking at it physically, the egg has transformed to another thing compared to how I was initially.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: