Why Some Things Will Not Mix: teacher key

Mixing and Reactions, grade 11 edition, written for 11th grade. Salt dissolves in water because of how water molecules pull on ions, while oil and water stay apart unless an emulsifier steps in. Collisions, activation energy, catalysts and enzymes then explain how fast reactions go.

Read the book. Print this page for the key.

Questions and answers

1. What happens to the positive side of a water molecule when salt dissolves?
   • It is attracted to chloride ions (answer)
   • It is attracted to sodium ions
   • It sticks to oil
2. Why does an instant cold pack get cold?
   • It gives off heat as it dissolves
   • Dissolving ammonium nitrate in water is an endothermic process (answer)
   • Oil forms an emulsion inside it
3. What is the activation energy?
   • The smallest energy a collision needs in order to make products (answer)
   • The heat given off by a flame
   • The average energy of all the molecules
4. Why does warming a sample usually make a reaction go faster?
   • It removes the catalyst
   • It puts more molecules above the activation energy (answer)
   • It makes the molecules slower
5. What can happen to an enzyme that gets too hot?
   • It binds more substrate
   • Its shape changes and it no longer works well (answer)
   • It turns into a catalytic converter
6. What did people not realize about foaming wine and beer until the 17th century?
   • That the foaming was a gas (answer)
   • That yeast was involved in bread
   • That the drinks could be made at all

Words

• solvent: dissolving liquid
• miscible: fully mixable
• emulsion: droplets in liquid
• equilibrium: steady balance
• denaturing: shape loss
• catalyst: speeds up reactions