If scientists want to determine if a skin cream is effective against fighting acne, what would be the independent variable?

What is the percentage by mass of silicon (si) in iron aluminum silicate (fe3al2(sio4)3)?

Acalorimeter is to be calibrated: 51.203 g of water at 55.2 degree c is added to a calorimeter containing 49.783 g of water at 23.5c. after stirring and waiting for the system to equilibrate, the final temperature reached is 37.6 degree c. specific heat capacity of water (s = 4.18 j/g∙degree c). calculate the calorimeter constant. (smδt)warm water = -[(smδt)cold water + (calorimeterδtcold water)]

What is one real world example of a colligative property?