What Makes a Reaction Hurry: teacher key

Mixing and Reactions, grade 7 edition, written for 7th grade. Reactions can speed up with heat, with fine powder, with more of a substance, or with a catalyst. Read how solutions work, why cold packs get cold and how eggs and dough change.

Read the book. Print this page for the key.

Questions and answers

1. In a solution, which part is present in the greater amount?
   • The solutes
   • The catalyst
   • The solvent (answer)
2. Why does an instant cold pack get cold?
   • Dissolving the salt takes in heat (answer)
   • Gravity pulls the salt down
   • The pack gives off heat
3. A cook wants a solid to react faster. Which is the best choice?
   • One big lump
   • Fine powder (answer)
   • A cooler room
4. What happens to a catalyst in a reaction?
   • It turns into gas
   • It becomes rust
   • It is not used up (answer)
5. What does the gas from yeast do to dough?
   • Expands the tiny air bubbles (answer)
   • Turns it blue
   • Dissolves it
6. What does endothermic mean for a process?
   • It goes slowly
   • It takes heat in (answer)
   • It makes gas

Words

• solvent: the part dissolving
• solutes: dissolved parts
• catalyst: reaction speeder
• endothermic: takes heat in
• fermentation: yeast gas making