Law of conservation of mass

• What is the law of conservation of mass?

  No atoms are lost or made in a chemical reaction.
• What happens to atoms during a chemical reaction according to the law of conservation of mass?

  Atoms join together in different ways to form products.
• Why is the number of atoms of each element the same on both sides of a balanced symbol equation?

  Because atoms are not lost or made in a chemical reaction.
• What is the relationship between the total mass of products and reactants in a chemical reaction?

  The total mass of the products is equal to the total mass of the reactants.
• What is relative formula mass?

  The sum of the relative atomic masses of the atoms in a chemical formula.
• How can the mass of one substance in a reaction be calculated?

  If the masses of the other substances are known.
• What is the process to find the total mass of calcium carbonate from its components?

  • Calcium carbonate is made up of 28 grams of calcium oxide and 22 grams of carbon dioxide.
  • Total mass = 28 g + 22 g = 50 g of calcium carbonate.
• How do you calculate the mass of oxygen produced in a reaction?

  • Given: 48 grams of magnesium and 80 grams of magnesium oxide.
  • Mass of oxygen = 80 g - 48 g = 32 g.
• What is a closed system in chemistry?

  A system in which no substances can enter or leave during a reaction.
• What happens to the total mass in a closed system during a reaction?

  The total mass stays the same during the reaction.
• What is a non-enclosed system in chemistry?

  A system in which gases or other substances can enter or leave during a reaction.
• What effect does escaping gas have on the perceived mass in a non-enclosed system?

  The total mass will appear to have decreased.
• What happens when a gas is gained in a non-enclosed system?

  The total mass will appear to have increased.
• What is the change in mass when calcium carbonate is heated in a thermal decomposition reaction?

  The mass appears to have decreased because carbon dioxide escapes to the air.
• What is the equation for the thermal decomposition of calcium carbonate?

  CaCO₃(s) → CaO(s) + CO₂(g)
• What is the total mass of solid and gas products in the thermal decomposition of calcium carbonate?

  The total mass will be 10.0 g.
• What are the differences between closed and non-enclosed systems in chemical reactions?

  Closed systems:

  • No substances can enter or leave.
  • Total mass remains constant.

  
  

  Non-enclosed systems:

  • Substances can enter or leave.
  • Total mass may appear to change due to gas escape or gain.