Physical and Chemical Changes Quiz
Questions: 16 · 10 minutes
1. An iron nail is left outdoors and gradually develops rust. Why is this a chemical change?
Iron reacts with substances in the environment to form new compounds
The nail's surface becomes rougher than before
The nail can still be recognized as a metal object
The change occurs slowly rather than immediately
2. Two clear solutions are mixed, and an insoluble solid appears even though no liquid evaporates. What is the best interpretation?
It must be a state change caused only by cooling
It is evidence of a chemical reaction because a new solid precipitate formed
It is physical because the solid has merely settled to the bottom
It is physical because all ingredients remain in the same container
3. Water vapor cools and forms droplets on the outside of a cold glass. What has happened?
The glass has reacted with water to produce a liquid coating
Water has decomposed because thermal energy was removed
A chemical change has occurred because droplets appeared
A physical change has occurred as water changed from gas to liquid
4. A piece of chalk is crushed into a fine powder. Which explanation is most accurate?
It is chemical because smaller particles have more surface area
It is chemical because the original piece cannot easily be restored
It is physical because the chalk's chemical identity remains unchanged
It is physical because changes involving solids cannot be chemical
5. A chemical reaction occurs inside a tightly sealed flask. Assuming nothing enters or leaves, what should happen to the flask's total mass?
It should decrease because reactants are used up
It should remain the same because matter is rearranged rather than destroyed
It should increase whenever a solid product forms
It should change according to the amount of energy released
6. An electric current passes through water and produces hydrogen and oxygen gases. How should this process be classified?
Chemical, because water is converted into substances with different identities
Physical, because electricity only changes the water's temperature
Physical, because all of the products are gases
A change of state, because liquid becomes gas
7. A cake batter is heated and becomes a cake with a new texture, aroma, and structure. Why is baking mainly classified as a chemical change?
The batter expands while it is heated
The finished cake has a different shape from the pan of batter
The oven removes some water from the batter
Ingredients undergo reactions that produce new substances and structures
8. A candle burns while wax near the flame melts. Which description correctly distinguishes the changes?
Both are physical because the candle remains visible
Both are chemical because heat is involved
Burning is physical, while melting is chemical
Melting is physical, while combustion of wax vapor is chemical
9. Methane burns in oxygen and produces carbon dioxide and water. What type of change occurs?
A chemical change, because the atoms are rearranged into different substances
A physical change, because the atoms themselves still exist
A change of state, because heat is released
A physical change, because gases are present before and after
10. In a physical change, what generally happens to the particles of a pure substance?
Their chemical bonds always break and form new compounds
Their atoms change into different elements
Their chemical identity stays the same, although their arrangement or spacing may change
Their mass disappears when the substance changes state
11. A mixture of iron filings and sand is separated with a magnet. What does this show about forming the mixture?
It was chemical because the iron interacted with the magnetic field
It was physical because the components retained their identities and could be separated
It was chemical because two substances occupied the same container
It was physical only because neither component was a liquid
12. Which statement about reversibility and types of change is scientifically accurate?
Reversibility can be a clue, but substance identity is a more reliable criterion
A change is chemical only when it cannot be reversed by any process
Every physical change is easily reversible
Any change that can be reversed must be physical
13. A copper wire is bent into a coil, while another copper object develops a green tarnish over time. Which event is a chemical change?
Bending the wire, because its shape changes permanently
Developing tarnish, because copper forms new substances at its surface
Both events, because copper looks different afterward
Neither event, because copper atoms remain present
14. Salt is dissolved in water and later recovered by evaporating the water. What does this best demonstrate?
Evaporation converted the salt into a new substance
Dissolving the salt was chemical because the solid disappeared
Dissolving the salt was a physical change because the original substances can be recovered
Both steps were chemical because heating was used
15. An ice cube melts in a glass without reacting with anything else. How should this change be classified?
Physical, because every change caused by warming is physical
Chemical, because liquid water has different properties from solid ice
Chemical, because energy is absorbed during melting
Physical, because the substance remains water while its state changes
16. Which observation provides the strongest evidence that a chemical change has occurred?
A solid is broken into several irregular pieces
Bubbles form throughout pure water as it reaches its boiling point
A gas forms when an acid is added to a carbonate rock at room temperature
Two differently colored powders are stirred together