1. An old, unpainted steel swing set in a park has developed a reddish-brown, flaky coating and is no longer considered safe. This is because the steel, which is mostly iron, has...
- A. been physically weathered by wind and rain until it became smaller.
- B. undergone a chemical reaction to form a weaker material.
- C. absorbed water, making it heavier and less stable.
- D. melted in the sun and re-solidified into a more brittle form.
2. When iron reacts to form iron oxide, the iron oxide is referred to as the...
- A. reactant.
- B. catalyst.
- C. product.
- D. solvent.
3. A city's old iron water pipes are failing due to rust. What is the most likely chemical reason for this infrastructure failure?
- A. The iron atoms in the pipes simply wore out and disappeared over time.
- B. The water pressure physically bent the pipes until they became brittle.
- C. The iron reacted to form a new, structurally weaker substance, iron oxide.
- D. The pipes expanded and contracted with temperature changes, causing cracks.
4. How do the properties of iron oxide (rust) compare to the properties of the original iron metal?
- A. Iron oxide is stronger and more flexible.
- B. Iron oxide is weaker and more brittle.
- C. Both substances have identical strength and structure.
- D. Iron oxide is a liquid, while iron is a solid.
5. During the formation of rust on an iron nail, what happens to the original iron atoms?
- A. They are destroyed and replaced by new rust atoms.
- B. They bond with other atoms to form a new compound.
- C. They change their physical state from a solid to a powder.
- D. They are washed away, leaving the weaker material behind.
6. In any chemical reaction, what is the role of the substances called "reactants"?
- A. They are the new substances created at the end of the reaction.
- B. They are the starting materials that interact and undergo a change.
- C. They are catalysts that speed up the reaction without being used up.
- D. They are the energy that is released or absorbed during the reaction.
7. Based on the process of rust formation on an iron object, which two elements are the primary reactants?
- A. Iron and Hydrogen
- B. Water and Rust
- C. Oxygen and Nitrogen
- D. Iron and Oxygen
8. What fundamental change occurs to the atoms of iron and oxygen during the chemical reaction that forms rust?
- A. The atoms are destroyed and new, different atoms are created.
- B. The atoms of iron transform into atoms of oxygen.
- C. The atoms are rearranged to form a new, more stable substance.
- D. The atoms are permanently fused without changing their original arrangement.
9. In the reaction that forms rust, iron and oxygen are the reactants. What is the resulting rust (iron oxide) itself considered?
- A. A catalyst
- B. A product
- C. An element
- D. A secondary reactant
10. An old iron nail is left in a shallow dish of water and begins to rust. From where do the oxygen atoms involved in this reaction primarily come?
- A. From the decomposition of the iron nail itself.
- B. From the water molecules (H₂O) and dissolved oxygen from the air.
- C. From the metal atoms within the nail's structure.
- D. From the hydrogen gas present in the atmosphere.