Conservation Of Mass Flashcards
(16 cards)
Q: What is the Law of Conservation of Mass?
A: Mass is not created or destroyed in a chemical reaction — the total mass of reactants equals the total mass of products.
Q: What must be true for a chemical equation to follow the Law of Conservation of Mass?
A: It must be balanced — the same number of each type of atom on both sides.
Q: Why does the mass stay the same in a closed system during a chemical reaction?
A: No particles can enter or leave; all atoms are accounted for.
Q: If 10g of hydrogen reacts with 80g of oxygen, what is the mass of the water produced?
A: 90g (10g + 80g)
In a reaction, 5g of magnesium reacts and 20g of oxygen is used. What is the total mass of magnesium oxide produced?
25g
Why might mass appear to change during a reaction in an open system?
A gas may be released into or from the surroundings
Q: Give an example where mass appears to increase in an open system.
Magnesium reacting with oxygen from the air — the mass of the product is greater than the metal alone
- Q: Give an example where mass appears to decrease.
When a metal carbonate is heated and releases CO₂ gas.
- Q: Is mass conserved in the reaction: CH₄ + 2O₂ → CO₂ + 2H₂O?
Yes — the same number and type of atoms are on each side
- Q: How do you prove mass is conserved in an experiment?
Measure total mass before and after in a closed container — it should be the same
Q: Why is it important to use a balanced equation when doing mass calculations?
A: Because unbalanced equations don’t reflect the actual proportions of atoms reacting.
Conservation of Mass
The total mass of of reactants equals the total mass of products
Closed System
A system where no matter can enter or leave
Open System
A system where matter can enter or escape, possibly affecting observed mass.
Balanced Equation
An equation with equal numbers of each type of atom on both sides.
Mass Change Misconception:
Mass only appears to change if gas enters or leaves the reaction area.
