Butter melt when you heat it in a pan on the stove. is this a chemical change or physical change? how can you tell?

How does the principle of electromagnetism explain the interaction between earth’s magnetic field and the solar wind?

Mike and mitchell decide to have a foot race. they mark off a stretch of 100 yards, and recruit cindy to work the stopwatch. after running the race and looking at the results, cindy declared that mitchell was the fastest. so how did the boys times compare?

What is the compound name for the formula [ru(en)2cl2]2+ and [co(en)cl2br]-