When Mixing Becomes a Reaction: teacher key

Mixing and Reactions, grade 4 edition, written for 4th grade. Some mixes only blend, and some make new stuff. Find out how chemists tell them apart, and one safety rule.

Read the book. Print this page for the key.

Questions and answers

1. What is a precipitate?
   • A bubble of gas
   • A solid that appears when clear liquids mix (answer)
   • A very even mix
2. On the pH scale, what is seven?
   • A strong acid
   • A base
   • Neutral (answer)
3. What holds oil and water together in mayonnaise?
   • Egg yolk (answer)
   • Vinegar
   • Salt
4. When things mix or react, what happens to the total amount of matter?
   • It grows
   • It stays the same (answer)
   • It shrinks
5. A liquid has a pH of 3. What is it?
   • A base
   • Neutral
   • An acid (answer)
6. Why should you never mix cleaning products?
   • They turn to rust
   • They can make fumes that are hard to breathe (answer)
   • They make an emulsion

Words

• solution: an even mix
• emulsion: spread-out drops
• precipitate: new solid
• indicator: a color clue
• neutral: in the middle