Chemical Reactions Vocabulary Quiz

Which of the following best describes an endothermic reaction?

• A reaction that gives off heat

• A reaction that absorbs heat

• A reaction that releases gas

• A reaction that changes color

Answer explanation

An endothermic reaction is characterized by the absorption of heat from the surroundings, making the correct choice "A reaction that absorbs heat." This contrasts with exothermic reactions, which release heat.

Which of these is an example of an endothermic process?

• Burning wood

• Rusting of iron

• Combustion of a match

• Dissolving ammonium nitrate in water

Answer explanation

Dissolving ammonium nitrate in water is an endothermic process because it absorbs heat from the surroundings, resulting in a temperature drop. In contrast, burning wood, rusting iron, and combustion release heat.

An exothermic reaction is one that:

• Absorbs energy

• Occurs slowly over time

• Releases heat into its surroundings

• Requires a catalyst to proceed

Answer explanation

An exothermic reaction is characterized by the release of heat into its surroundings, making 'Releases heat into its surroundings' the correct choice. The other options describe different types of reactions or processes.

Which example represents an exothermic reaction?

• Freezing water

• Mixing vinegar with baking soda

• Burning a candle

• Dissolving sugar in water

Answer explanation

Burning a candle is an exothermic reaction because it releases heat and light as the wax combusts. In contrast, freezing water and dissolving sugar in water are endothermic processes, while mixing vinegar and baking soda produces gas without heat release.

A precipitate is defined as:

• A solid that forms and separates from a solution

• A dissolved substance

• A gas produced during a reaction

• A liquid that evaporates

Answer explanation

A precipitate is specifically defined as a solid that forms and separates from a solution during a chemical reaction, making this the correct choice. The other options describe different states of matter or processes.

Which everyday example is a precipitate?

• Fog

• Scale formation inside a kettle

• Steam from boiling water

• Oil mixed in vinegar

Answer explanation

Scale formation inside a kettle is a precipitate, as it forms when dissolved minerals in water crystallize and settle out. In contrast, fog, steam, and oil in vinegar do not involve solid particles forming from a solution.

A chemical property is best described as a characteristic that can be observed when:

• A substance undergoes a chemical reaction

• A substance changes its physical form

• A substance is cooled down

• A substance is mixed with water

Answer explanation

A chemical property is observed when a substance undergoes a chemical reaction, as this involves changes in its chemical structure. The other options describe physical changes, not chemical properties.

Which of the following is a chemical property?

• Color

• Melting point

• Reactivity with an acid

• Solubility in water

Answer explanation

Reactivity with an acid is a chemical property because it describes how a substance interacts with another substance, leading to a chemical change. In contrast, color, melting point, and solubility are physical properties.

A physical property can be observed without changing the substance’s:

• State of matter

• Temperature

• Volume

• Chemical composition

Answer explanation

A physical property can be observed without altering the substance's chemical composition. Observing properties like color or density does not change what the substance is made of, unlike changes in state, temperature, or volume.

Which of these is an example of a physical property?

• Flammability

• Density

• Hardness

• Reactivity

Answer explanation

Density is a physical property that describes how much mass is contained in a given volume. In contrast, flammability, hardness, and reactivity are chemical properties or characteristics related to a substance's behavior.