7. Which of the following temperature changes is NOT the result of a chemical change?

Question

a rise in temperature as neutralisation takes place
2. a rise in temperature when a fuel burns
3. a fall in temperature as a precipitate falls
4. a fall in temperature as liquid metal cools to solidify

Answer 1

A fall in temperature as liquid metal cools to solidify.

 

This is a physical change. Analyzing the other options will help explain why.

 

1: The definition of a neutralization IS what makes it a chemical change. Two charged species neutralize one another which is a chemical, not a physical process.

 

2: Fuel burns due to the combustion (i.e. reaction with oxygen) of some organic substrate. This makes it a chemical process.

 

3: Formation of precipitate in solution occurs because atoms are rearranged to form stronger ionic bonds (or covalent bonds - I'm not sure what level chemistry you are in).

 

4: This is a physical process because the liquid metal does not undergo any chemical change. The identity of the liquid metal is the same as its solid. Therefore, the metal is not undergoing a chemical change.