which one of the following is an example of physical change?

Question

a) the evaporation of water
b) the rusting of iron
c) the combustion of hydrogen
d) the tarnishing of silver
e) bothe the rusting of iron and the tarnishing of silver

Answer 1

Evaporation of water: water turns into steam or water vapor. It's still water (H2O). Same molecule, same chemistry...just different state. So it's a physical change.

Rusting of iron: Iron combines with oxygen in the air to turn to rust. Rust is a different compound from pure iron. So it's a chemical change. The reaction is iron + oxygen -> rust, or 4 Fe + 3 O2 -> 2 Fe2O3.

Combustion of hydrogen: Hydrogen burns with oxygen in the air to turn to water. Hydrogen and water are not the same, so it's a chemical change.

Tarnishing of silver: This is like rusting, so silver combines with oxygen to form a silver oxide. This is again a chemical change. (People who said it's physical probably don't know what tarnishing is.)

So anything that involves atoms or molecules combining (or splitting) and forming new atoms or molecules is a chemical change. Anything that keeps the same atoms and molecules, just in a different form, is a physical change.

Answer 2

e) Both the rusting of iron and the tarnishing of silver

Answer 3

A evaporation of water bcz it's just chage of state

Answer 4

evaporation of water (others are chemical changes)

Answer 5

a) the evaporation of water

Answer 6

Technically, by definition they're all examples of physical change.

Answer 7

A, it just change its phase from liquid to gas.

Answer 8

a) because it just changed state. vapor can be change back to water if it can't be change back then it's a chemical change

Answer 9

a

Answer 10

physical change: Turns to ice, liquid, or gas

if it doesn't do one of those three then it's not a physical change.