Question

it is important to understand the differences between chemical and physical changes. chemical changes result in new substances, but physical changes do not. which process is an example of a physical change? water breaks down into hydrogen and oxygen gases over time. limestone breaks down into lime and carbon dioxide when heated. water turns to steam when boiled over a bunsen burner. carbon combines with oxygen to form carbon dioxide gas.

Explanation:

• Water breaks down into hydrogen and oxygen gases over time: This is a chemical change as new substances (hydrogen and oxygen) are formed. The chemical formula for water is \(H_2O\), and hydrogen is \(H_2\) and oxygen is \(O_2\). A chemical reaction \(2H_2O

ightarrow2H_2 + O_2\) occurs.

• Limestone breaks down into lime and carbon dioxide when heated: Limestone (\(CaCO_3\)) decomposes into lime (\(CaO\)) and \(CO_2\) (\(CaCO_3

ightarrow CaO+CO_2\)). New substances are formed, so it is a chemical change.

• Water turns to steam when boiled over a Bunsen burner: This is a physical change. Water (\(H_2O\)) in liquid state changes to gas (steam) state. The chemical composition (\(H_2O\)) remains the same. It is just a change of state (liquid - gas) due to heat.
• Carbon combines with oxygen to form carbon dioxide gas: \(C + O_2

ightarrow CO_2\). New substance (\(CO_2\)) is formed, so it is a chemical change.

Answer:

Water turns to steam when boiled over a Bunsen burner.