Which of these is an example of a chemical change? dissolving two cups of flour in a liter of water pouring water from a large trough into a beaker decreasing the motion of water molecules by freezing forming oxygen by bubbling fluorine through water

Forming oxygen By bubbling flourine through water

Explanation:

Chemical change is the change in which chemical composition of the substance changes by rearrangement of atoms.

Physical change is a change in which only the physical properties such as size, shape etc change and there is no rearrangement of atoms.

1. Dissolving two cups of flour in a liter changes the state and hence is a physical change.

2. Pouring water from a large trough into a beaker is a physical change.

3. Decreasing the motion of water molecules by freezing changes the state and hence is a physical change.

4. Forming oxygen By bubbling flourine through water involve rearrangement of atoms and thus is a chemical change.

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explanation:

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.