Is it true oxygen is an excellent solvent that is capable of dissolving just about anything?

Which real-world scenarios below represent physical and chemical changes? -running a car -exploding fireworks -mixing water and powdered drink mix -combining oil and vinegar to make salad dressing -taking aspirin for a headache -diluting bleach with water-digesting dinner-spreading peanut butter on bread

What does the cell nucleus do or, how does it function?

What layer of the atmosphere is directly above the troposphere?