3.1.1 Law of conservation of mass in chemical reactions

• What remains the same throughout a chemical reaction?

  Number and type of atoms
• How do you start balancing the equation H₂ + O₂ → H₂O?

  Write the chemical equation
• What is the chemical formula for water?

  H2O
• How can you write the balanced chemical equation for the reaction shown?

  Balanced chemical equation:

  $CH_4 +$$2O_2 \rightarrow CO_2 +$$2H_2O$
• How can you determine the coefficients in the balanced chemical equation?

  To balance the equation:

  • Count the number of atoms of each element on each side
  • Adjust the coefficients so the number of atoms of each element is equal on both sides
• What is produced when iron rusts?

  Rust (Iron Oxide)
• In an open system, what can be exchanged with the surroundings?

  Both matter and energy
• What coefficient is added in front of H₂O to balance oxygen in H₂ + O₂ → H₂O?

  2
• What law does balancing chemical equations follow?

  Law of Conservation of Mass
• What does the arrow in a chemical equation indicate?

  The direction of the reaction
• What is the chemical formula for carbon dioxide?

  CO2
• What are the three main applications of the Law of Conservation of Mass in quantitative chemistry?

  • Determining reactant amounts
  • Calculating product yields
  • Standardising solutions
• What does the balanced equation 2H₂ + O₂ → 2H₂O demonstrate about chemical reactions?

  • Conservation of mass is upheld
  • Equal number of atoms for each element
  • Molecules react in specific ratios
• What are the substances that start a chemical reaction called?

  Reactants
• Why is standardising solutions important in quantitative chemistry?

  It ensures accurate concentration measurements.
• Why is the Law of Conservation of Mass more accurate in closed systems?

  Because total mass remains constant
• What distinguishes an open system from a closed system in chemical reactions?

  • Open System:
  • Matter exchange: Yes
  • Energy exchange: Yes
  • Example: Boiling water in an open pan
  • Closed System:
  • Matter exchange: No
  • Energy exchange: Yes
  • Example: Boiling water in a sealed pressure cooker
• Why is the mass balance important in chemical reactions?

  It demonstrates that mass is conserved
• How do the applications of the Law of Conservation of Mass help chemists?

  • Plan experiments effectively
  • Achieve precise results
  • Maintain mass balance in reactions
• What are the two types of systems in chemical reactions?

  Open and closed systems
• In a closed system, what can be exchanged with the surroundings?

  Only energy
• What happens to the weight of ingredients when baking bread?

  The weight does not change after baking
• How does energy exchange differ between open and closed systems?

  Both systems allow energy exchange