Chemical reactions

Definition

Chemical reactions are processes in which substances, known as reactants, undergo a transformation to form new substances called products. These reactions involve the breaking and forming of chemical bonds, leading to changes in the arrangement of atoms. Understanding chemical reactions is crucial as they are fundamental to the behavior of matter and the principles underlying the atomic theory.

5 Must Know Facts For Your Next Test

1. Chemical reactions can be categorized into different types, including synthesis, decomposition, single replacement, double replacement, and combustion.
2. In any chemical reaction, energy changes occur; reactions may either absorb energy (endothermic) or release energy (exothermic).
3. The speed at which a chemical reaction occurs can be influenced by factors such as temperature, concentration, surface area, and the presence of catalysts.
4. Balancing chemical equations is essential to ensure that the law of conservation of mass is obeyed; this requires that the number of atoms for each element is equal on both sides of the equation.
5. Chemical reactions play a vital role in everyday life, including processes like digestion, combustion in engines, and photosynthesis in plants.

Review Questions

• How do reactants transform into products during a chemical reaction?
  • Reactants transform into products through the breaking and forming of chemical bonds. During this process, atoms rearrange themselves into new configurations, leading to the creation of different substances. The chemical properties of the reactants may differ significantly from those of the products due to these changes in atomic arrangements.
• Discuss how energy changes affect the nature of chemical reactions and give examples.
  • Energy changes play a significant role in determining whether a chemical reaction is endothermic or exothermic. Endothermic reactions absorb energy from their surroundings, often resulting in a temperature drop, while exothermic reactions release energy, typically causing a temperature increase. For example, combustion reactions are exothermic because they release heat and light, whereas photosynthesis is endothermic as it absorbs sunlight to convert carbon dioxide and water into glucose and oxygen.
• Evaluate the importance of balancing chemical equations and its implications for the law of conservation of mass.
  • Balancing chemical equations is crucial because it reflects the law of conservation of mass, which states that matter cannot be created or destroyed. When equations are balanced, it ensures that the same number of each type of atom is present on both sides of the equation. This practice not only helps chemists accurately represent reactions but also allows for calculations regarding reactants and products in various applications, emphasizing its significance in both theoretical and practical chemistry.

Related terms

reactants: The starting substances in a chemical reaction that undergo transformation during the reaction.

products: The substances formed as a result of a chemical reaction after the reactants have undergone transformation.

conservation of mass: A principle stating that mass is neither created nor destroyed in a chemical reaction; the total mass of reactants equals the total mass of products.