Cambios Químicos y Reacciones

Chemical Changes and Reactions

• Chemical reactions involve breaking chemical bonds in reactants and forming new bonds in products.
• Reactants are the initial substances, while products are the resulting substances.
• Conditions for chemical changes include mixing (contact), heating, light, electricity, and pressure.

Types of Chemical Changes

• Direct Combination/Synthesis: Two or more substances combine to form a single substance (e.g., 2Mg + O₂ → 2MgO).
• Decomposition: A compound breaks down into simpler substances (e.g., 2HgO → 2Hg + O₂).
• Displacement: One element replaces another in a compound (e.g., CuSO₄ + Zn → ZnSO₄ + Cu).
• Double Decomposition/Metathesis: Two compounds exchange elements to form two new compounds (e.g., NaCl + AgNO₃ → AgCl + NaNO₃).

Energy Changes

• Exothermic Reactions: Release heat (e.g., burning fuels).
• Endothermic Reactions: Absorb heat (e.g., photosynthesis).

Chemical Reactions involving heat

• Thermal Decomposition: Decomposition reaction caused by heat (e.g., heating copper carbonate).
• Combination Reactions: Combination of elements or compounds due to heat (e.g., combustion of magnesium + oxygen).

Catalysts

• Catalysts speed up or slow down reactions without being consumed.
• Positive catalysts speed up reactions; negative catalysts slow them down.

Chemical Reactions involving electricity

• Electrolysis of water using electricity (e.g., 2H₂O → 2H₂ +O₂).
• Electrolysis of sodium chloride (e.g., 2NaCl → 2Na + Cl₂).

Chemical Reactions involving Pressure

• Some reactions need high pressure to proceed (e.g., the formation of ammonia N₂ + 3H₂ → 2NH₃ Requires high pressure).

Other Important characteristics of chemical Reactions

• Precipitate formation: Formation of insoluble substances (e.g., a white ppt. of silver chloride).
• Color change: Change in the color of the substances during a reaction (e.g., reaction of iron with copper sulfate solution).
• Evolution of Gas: Formation of gas in a reaction . (e.g., evolution of carbon dioxide).
• Change of state: Change of a substance from one state to another (e.g., water boiling to form gas).

Chemical Reactions Applications

• Digestion in the body: Food decomposition and energy production.

Este cuestionario abarca los cambios químicos y las reacciones que impliquen la ruptura y formación de enlaces químicos. Se discutirán los tipos de reacciones, así como los cambios de energía asociados como las reacciones exotérmicas y endodérmicas. Prepárate para explorar el fascinante mundo de la química.