Which of these is an example of a physical change -baking a cake -toasting bread -grinding pepper -lighting up a grill

Your best choice would be grinding pepper

Grinding paper because a physical change is where it’s still the same subsctance, not a chemical because chemical is when it changes into a new substance like toasting bread, the burnt parts are a new substance, it changes it. But grinding pepper isn’t changing the substance it’s just making it into little pieces

Thermohaline circulation and gyres

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .