Balance It!
Balance: H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
Write the word equation for: H₂ + O₂ → H₂O
Hydrogen + oxygen → water
What does the law of conservation of mass state?
Mass cannot be created or destroyed in a chemical reaction
What is the product in this equation? Mg + O₂ → MgO
Magnesium oxide
What planet is known as the Red Planet?
Mars
Balance: Mg + O₂ → MgO
2Mg + O₂ → 2MgO
Magnesium reacts with oxygen to form magnesium oxide.
Magnesium + oxygen → magnesium oxide
Why must equations be balanced?
To show equal numbers of each atom on both sides
Balance: Al + O₂ → Al₂O₃
4Al + 3O₂ → 2Al₂O₃
What animal can sleep for up to 20 hours a day?
Koala
Balance: Na + Cl₂ → NaCl
2Na + Cl₂ → 2NaCl
Iron reacts with sulfur to form iron sulfide.
Iron + Sulfur → Iron sulfide
If 10 g of hydrogen reacts with 80 g of oxygen, what mass of water is produced?
90g
Write the word equation for: Fe + S → FeS
Iron + Sulfur → iron sulfide
Which came first: the chicken or the egg?
Egg, obviously.
Balance: CH₄ + O₂ → CO₂ + H₂O
CH₄ + 2O₂ → CO₂ + 2H₂O
Hydrogen peroxide decomposes into water and oxygen.
Hydrogen peroxide → Water + Oxygen
A reaction loses mass in an open beaker. Why might this happen?
Gas may have escaped into the air
Why can’t subscripts be changed when balancing equations?
Changing subscripts changes the substance itself
Yes or no?
Yes
Balance: Fe₂O₃ + C → Fe + CO₂
2Fe₂O₃ + 3C → 4Fe + 3CO₂
Carbon dioxide and Water are formed when Methane burns with Oxygen.
Methane + Oxygen → Carbon dioxide + Water
Explain why atoms are rearranged rather than created or destroyed in reactions
Atoms are rearranged into new substances but total atoms stay the same
A student says: “Mass disappeared during the reaction.” Explain why this statement is incorrect
Mass was not destroyed — matter likely escaped as a gas or was not measured properly
Mr. Coates' favourite colour?
Purple