Which of the following is an example of physical change?
1) A Halloween light stick glows after shaking
2) An oxygen balloon explodes when contacted with a flame.
3) browning meat
4) Steam condensed on the mirror after taking a shower.
5) None of the above is a physical change.

2 and 4

Explanation:

The rest of the changes are chemical. 1 has a chemical reaction happen which makes light sticks glow. 3 is because browning the meat actually causes some new compounds to form and cause caramelization.

For 2, the oxygen is simply heating up and expanding which pops the balloon. 4 is just a phase change of water vapor to liquid water.

what is the general relationship between a galaxy's distance from earth and its speed?

the answer is:

the farther away a galaxy is from us, the faster it is moving away from us.

"the periodic table is arranged in order of atomic number."