Classify the following as chemical or physical properties: (a) the color of copper(II) sulfate is blue; (b) the melting point of sodium metal is \(97.8^{\circ} \mathrm{C}_{i}\) (c) iron rusts in arcas with high humidity.

Chemical properties define a substance's potential to undergo a chemical change, transforming into a new substance with different characteristics. These properties are intrinsic to the substance, meaning they are inherent and do not change unless the substance itself changes. Understanding chemical properties is crucial in predicting how a substance will behave in a chemical reaction. For example, the reactivity of a substance with acids or bases, its flammability, or its tendency to oxidize, as in the case of iron rusting in humid conditions, are all chemical properties. The rusting process is indicative of a chemical property because iron, when exposed to oxygen and moisture, undergoes a transformation to create iron oxide, a different compound with a distinct chemical structure and properties compared to the original iron.

• Reactivity with other chemicals
• Oxidation states
• Flammability

Rusting, as in the original exercise, highlights a material's susceptibility to oxidization, a fundamental chemical property.

Physical properties are the characteristics of a substance that can be observed or measured without changing the substance's chemical identity. These include attributes such as color, phase (solid, liquid, or gas), melting and boiling points, density, and electrical conductivity. For instance, the color of copper(II) sulfate being blue or the melting point of sodium metal being at \(97.8^\circ \mathrm{C}\) are both physical properties because observing these does not require altering the chemical composition of the substances. By identifying the physical properties, we can describe and categorize materials based on observable criteria without the need for a chemical reaction.

• Melting/boiling point
• Density and phase
• Color and electrical conductivity

These properties are essential in material science and help in everyday decisions, like choosing materials based on their thermal or electrical conductivities.

State change, also known as a phase change, refers to the transition of a substance from one state of matter (solid, liquid, or gas) to another due to a change in temperature or pressure. Comprehending state changes is fundamental in both scientific and practical applications. When a solid melts, becoming a liquid, or a liquid evaporates into a gas, these changes are typically physical processes that do not affect the actual chemical structure of the substance. Hence, state changes are associated with physical properties. Common state changes include melting, freezing, vaporization, condensation, sublimation, and deposition. The provided exercise example, where the melting point of sodium metal is \(97.8^\circ \mathrm{C}\), represents the temperature at which sodium undergoes a state change from solid to liquid.

• Melting and freezing points
• Vaporization and condensation points
• Sublimation and deposition processes

Identifying the conditions under which these phase changes occur is critical for many industries, including culinary arts, metallurgy, and the creation of various materials and products.

Chemical reactions are processes where reactants transform into products through the breaking and forming of chemical bonds, resulting in substances with different chemical properties. During a chemical reaction, one or more new compounds are created, and energy may be absorbed or released. Reactions are often characterized by changes in temperature, color, the formation of a precipitate, or gas production.An understanding of chemical reactions is essential across multiple fields, from biochemistry to industrial manufacturing. In the classroom context of identifying chemical properties, the rusting of iron is a prime example of a chemical reaction. This process, known as oxidation, converts the elemental iron into iron oxide through its interaction with moisture and oxygen in the air.

• Indicators of chemical reactions include energy changes, gas evolution, and color change.
• The conservation of mass applies to reactions, meaning the total mass of reactants equals the total mass of products.
• The rate of a reaction can be affected by factors such as temperature, concentration, and the presence of a catalyst.

A firm grasp of chemical reactions allows students to comprehend and predict the behavior of substances, as well as to safely execute experiments in a laboratory setting.