Mass stays the same in a reaction

Answer Key - Grade 8 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   In a teacher's sealed flask, 84 g of baking soda reacts with 60 g of the acid in vinegar. Sodium acetate and water total 100 g. What mass of carbon dioxide formed, Ari?

   44 g
2. 2.

   A stove flame joins 16 g of methane with 64 g of oxygen. It makes 44 g of carbon dioxide and some water. What mass of water forms, Bo?

   36 g
3. 3.

   In Esme's cells, 180 g of glucose and 192 g of oxygen can release energy, making 264 g of carbon dioxide and some water. What mass of water?

   108 g
4. 4.

   Jun's mass graph is flat at 500 g, falls to 492 g, then levels off. Which story fits the graph?

   • A sealed flask leaked air in
   • Mass was destroyed while the tablet fizzed
   • Water was poured in at 2 min
   • A tablet fizzed in an open flask until it stopped
5. 5.

   Kira's mass graph rises slowly from 200 g to 206 g over 6 days. Which story fits the graph?

   • Rust made new matter from nothing
   • Steel wool rusted in an open dish
   • Steel wool rusted in a sealed jar
   • Water evaporated from the dish
6. 6.

   Luz's mass graph stays flat at 350 g while the liquid changes color. Which story fits the graph?

   • Mass was made and destroyed in equal amounts
   • A reaction ran in a sealed flask
   • No reaction, since the mass stayed the same
   • A gas escaped from an open flask
7. 7.

   Now the candle burns on the scale with no jar over it. What does Noah predict for the reading?

   • It drops as gases rise away
   • It rises: the flame adds mass
   • It stays the same: mass is conserved
   • It drops to 0 g at once
8. 8.

   Steel wool sits in an open dish on a scale for a week and rusts. What does Pia predict for the reading?

   • It rises as oxygen joins
   • It stays the same: mass is conserved
   • It drops to 0 g
   • It drops: rusting wears away iron
9. 9.

   Ren says the gas from a fizzing tablet weighs nothing, so it can't change the scale. Agree or disagree?

   • Disagree: gases have mass
   • Agree: gases float, so weigh nothing
   • Disagree: gas makes the cup heavier
   • Agree: bubbles are just empty space
10. 10.

    Tala says a burned log proves that burning destroys mass. Agree or disagree?

    • Agree: fire uses up matter
    • Disagree: ash is heavier than the log
    • Disagree: the mass left as gases
    • Agree: the ash is lighter, so mass was destroyed