Question

Which observations below describe chemical properties? (a) Sugar is soluble in water. (b) Water boils at \(100^{\circ} \mathrm{C}\) (c) Ultraviolet light converts \(\mathrm{O}_{3}\) (ozone) to \(\mathrm{O}_{2}\) (oxygen). (d) Ice is less dense than water.

Short answer

The chemical property is described in observation (c).

Step-by-step solution

Understanding Chemical Properties

Chemical properties describe a substance's potential to undergo chemical change or reaction by forming new substances. Unlike physical properties (such as boiling points and solubility), chemical properties involve a change in the chemical structure of the substance.

Analyzing Option (a)

Option (a) states "Sugar is soluble in water." Solubility is a physical property because dissolving sugar in water does not change its chemical composition, it merely dissolves physically.

Analyzing Option (b)

Option (b) states "Water boils at \(100^{\circ} \mathrm{C}\)." Boiling merely changes water from a liquid to a gas, which is a physical change. Thus, boiling points signify a physical property, not a chemical one.

Analyzing Option (c)

Option (c) states "Ultraviolet light converts \(\mathrm{O}_{3}\) (ozone) to \(\mathrm{O}_{2}\) (oxygen)." This involves breaking and forming chemical bonds to change ozone into oxygen, indicating a chemical reaction. Therefore, this is a chemical property.

Analyzing Option (d)

Option (d) states "Ice is less dense than water." Density differences stem from physical changes in state and molecular arrangement, not from a change in chemical composition. Therefore, this is a physical property.

Identify the Correct Observation

Based on the analysis, the option that describes a chemical property is (c): "Ultraviolet light converts \(\mathrm{O}_{3}\) (ozone) to \(\mathrm{O}_{2}\) (oxygen)" because it describes a chemical reaction.

Key concepts

chemical change

A chemical change represents a transformation where substances convert into different substances. When a chemical change occurs, the molecules are rearranged, leading to new chemical structures and properties. These changes are often identified by observable factors such as color change, gas production, heat emission, or the formation of a precipitate.

Chemical changes are crucial in understanding how different elements and compounds interact within chemical reactions. For example, the conversion of ozone ( O_3 ) to oxygen ( O_2 ) when exposed to ultraviolet light is a chemical change because ozone undergoes a structural shift, resulting in a different substance. This signifies a change in chemical composition, marking it as a chemical property rather than merely a change in state or form.

chemical reaction

Chemical reactions are processes wherein substances, known as reactants, interact to form new substances, known as products, with distinct chemical properties. In a chemical reaction, bonds between atoms in the original substances are broken and new ones are formed in the products. This rearrangement of atoms and alteration of chemical bonds is what fundamentally differentiates a chemical reaction from a mere physical process.

Chemical reactions can be exothermic, emitting heat, or endothermic, absorbing heat. They might also involve changes in light or electricity. Observing the transformation of ozone into oxygen under ultraviolet light encapsulates these concepts, as it involves a change from one compound to another through a chemical reaction, confirming the substance's chemical property.

physical properties

Physical properties are characteristics that can be measured or observed without changing the chemical nature of a substance. These include attributes like color, density, boiling and melting points, and solubility. Unlike chemical properties, physical properties do not involve forming new substances.

• Boiling point, as observed with water, indicates the temperature at which it turns to gas, exemplifying a physical change.
• Density represents how compact the matter is in a substance, as ice being less dense than water showcases.
• Solubility is how well a substance dissolves in a solvent, like sugar in water, representing a physical transformation.

These properties are essential for identifying substances and understanding how they might behave in different environments without undergoing a chemical transformation.

solubility vs chemical reaction

Understanding the difference between solubility and a chemical reaction is key in distinguishing between physical and chemical properties. Solubility is the capacity of a substance to dissolve in a solvent, resulting in a solution. This process retains the original substance's chemical identity and composition, illustrating a physical property.

Alternatively, a chemical reaction involves a substantive change where the chemical identity of the substance is altered. In a chemical reaction, new molecules are formed, as seen when ozone is transformed into oxygen. This change indicates a chemical property because there is a conversion into new substances, a drastic shift from the initial state.

• Solubility leads to a physical dispersion of molecules within a solvent.
• Chemical reactions involve the breakdown and creation of new chemical bonds leading to different substances.

Recognizing these differences enhances one’s ability to categorize and predict the behaviors and properties of substances during experimental observations.