Which activity involves only a physical change?

a. acid bubbling on a rock
b. grinding coffee beans
c. exploding fireworks
d. baking cookies

Anybody who knows ap biology, can you friend or message me

Sally and sue were investigating the topic of friction in science. they used a small car and a ramp as seen in the picture to test what they were learning. they knew that they slipped easily on waxed floors but not on carpet, so they decided to change the material on the surface of the ramp to see what happened. they planned to use glass, carpet, aluminum foil, and sandpaper and run the car down the ramp over each surface. what would be the best research question to guide the girls' experiment? a) does the amount of surface area affect the friction on the moving car? b) will the car travel fastest on the glass surface? c) how does the angle of the ramp affect the speed of the car? d)do rougher surfaces tend to create more friction than smooth surfaces?

Which is an innovation of gymnosperms? gymnosperms are the first seed plants. gymnosperms are the first flowering plants. gymnosperms are the first vascular plants. gymnosperms are the first spore plants.