Chapter 21 Quiz

is a negatively charged particle that orbits the nucleus.

• Electron
• Proton

• Neutron

• Photon

Answer explanation

An electron is a negatively charged particle that orbits the nucleus of an atom. Protons are positively charged, neutrons are neutral, and photons are particles of light, making electron the correct choice.

Identify the choice that best completes the statement or answers the question. An example of an exothermic reaction is:

• refining aluminum ore.

• changing water to steam.

• heating “meals-ready-to-eat” (MREs) by pouring water into the ration heater.

Answer explanation

Heating MREs involves an exothermic reaction where chemical energy is released as heat when water activates the ration heater, making it the correct example of an exothermic process.

Classify the following reaction: Cu(OH)₂ → CuO + H₂O

• Addition

• Single-displacement

• Double-displacement

• Decomposition

Answer explanation

The reaction Cu(OH)2 → CuO + H2O involves the breakdown of a single compound into two products, which classifies it as a decomposition reaction.

When you activate an instant cold pack, water mixes with a chemical, and the pack gets very cold. This is an example of:

(a)  

• an endothermic reaction.
• an exothermic reaction.

• a combustion reaction.

• a physical change.

Answer explanation

When water mixes with the chemical in the cold pack, it absorbs heat from the surroundings, resulting in a temperature drop. This process is characteristic of an endothermic reaction, where energy is absorbed.

Identify the type of reaction: Zn + CuSO₄ → ZnSO₄ + Cu

• Addition

• Single-displacement

• Double-displacement

• Decomposition

Answer explanation

This reaction is a single-displacement reaction because zinc (Zn) displaces copper (Cu) from copper sulfate (CuSO4), forming zinc sulfate (ZnSO4) and elemental copper.

​ This is the term used to describe the charge of an atom when it gains or loses electrons to form a stable compound.

• Molecule

• Atom

• Electron

• Ion

Answer explanation

An ion is formed when an atom gains or loses electrons, resulting in a net charge. This charge allows ions to form stable compounds, distinguishing them from neutral atoms and molecules.

A chemical bond that occurs when atoms share electrons is a(n) (a)   bond.

• Covalent

• Ionic

• Metallic

• Hydrogen

Answer explanation

A covalent bond forms when atoms share electrons, allowing them to achieve stability. This is distinct from ionic bonds, which involve electron transfer, and metallic bonds, which involve a sea of shared electrons. Hydrogen bonds are weaker interactions.

A (a)   chemical equation has the same number of atoms of each element on each side of the equation.

• balanced

• unbalanced

• reactants

• products

Answer explanation

A balanced chemical equation has equal numbers of each type of atom on both sides, ensuring the law of conservation of mass is upheld. Therefore, the correct answer is 'balanced'.

Which of the following could represent a decomposition reaction?

• compound + compound = compound + compound

• compound = element + element

• element + element = compound

Answer explanation

A decomposition reaction involves breaking down a compound into simpler substances, typically elements. The correct choice, 'compound = element + element', illustrates this process, while the other options do not represent decomposition.

A chemical symbol represents the (a)   of an element.

• Element

• Compound

• Molecule

• Ion

Answer explanation

A chemical symbol uniquely identifies an element, representing its name in a standardized format. Therefore, the correct answer is 'Element', as it directly corresponds to what a chemical symbol signifies.