Which is an example of a physical change?
a. growing taller
b. digesting your food
c. getting a suntan
d. cutting your hair

Does anyone know a lot about how to: - calculate mass of magnesium metal - calculate the actual yield of magnesium oxide - calculate the theoretical yield of mgo - calculate the percent yield of mgo - determine the percent yield of mgo - determine the average percent yield of mgo i had to do an online lab and its asking these questions but i have no idea where to start or how to be able to find these things. i can post the chart of the data from the lab or if you can tell me exactly how i can find each.

Sandy is building a small toy car. he wants to use a balloon to power the toy car. he fills a balloon with air and then attaches a straw to the balloon. he tapes the balloon-straw combination to the car and then releases the end of the balloon. the toy moves forward as the air from the balloon comes out the back of the straw. what can sandy do to make the toy car move faster? a) use less air in the balloon. b) blow up the balloon more. c) use a longer straw. d) use larger tires.

How does water evaporating from a glass show that matter is made up of particles? a. the heat energy from the air causes the glass to fill up with water particles. b. the liquid water particles turn into water vapor that spreads in the air. c. the particles of the glass dissolve in water and cause it to evaporate. d. the tiny particles of the glass evaporate and seem to disappear.