Saturated and Supersaturated: teacher key

Mixing and Reactions, grade 8 edition, written for 8th grade. Mixes have limits, signs and speeds. Read how scientists measure how much can dissolve, why drinks go flat, what enzymes do and why bread crust tastes brown and sweet.

Read the book. Print this page for the key.

Questions and answers

1. What is a solution called when it holds more solute than the most that can dissolve?
   • Supersaturated (answer)
   • Saturated
   • Neutral
2. A glass of cold water is left out. Why do bubbles of air appear as it warms?
   • Gases dissolve better in warm water
   • Gases dissolve less well in warm water (answer)
   • Gases turn to salt
3. What is the Tyndall effect?
   • A colloid's heat
   • A fizzy drink
   • Particles large enough to scatter light (answer)
4. What does lecithin do in mayonnaise?
   • Holds droplets of oil in water (answer)
   • Makes the oil float
   • Gives off heat
5. How much faster can enzymes make reactions go?
   • Ten times
   • 100 million to 10 billion times (answer)
   • A hundred times
6. What does an emulsifying agent do?
   • Warms the mix
   • Turns it to gas
   • Stops the drops from joining (answer)

Words

• solubility: how much dissolves
• saturated: full of solute
• colloid: cloudy mix
• emulsifying: keeping drops apart
• caramelization: sugar browning