What Does Spit Do?

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Some animals can swallow food whole, but humans have to chew. In this activity, learners will investigate what saliva does chemically to food before we even swallow. Learner will examine how their own saliva affects a mashed-up cracker by using iodine to differentiate sugar and starch. Experiment can also be used on other foods like breakfast cereal. Step-by-step instructions are included with photos. Activity guide includes a "What's going on?" explanation and connections to relevant science concepts like enzymes in saliva, digestion, and salivary glands.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
30 to 45 minutes

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 6 - adult

Resource Types:
Activity, Experiment/Lab Activity


Materials List (per group of students)

  • pinch of cornstarch
  • pinch of granulated sugar
  • cracker
  • resealable plastic bad (sandwich size)
  • cup of water
  • 4 small spoons
  • 4 small cups
  • set of measuring spoons
  • small bottle of iodine
  • masking tape
  • marker


  • Life Sciences
    • Human Body
      • Digestion
  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Chemistry of Life

Informal Categories

  • Food and Cooking


Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access


Source Collection

  • DIY Science Apps


  • , The Regents of the University of California, 2015

Funding Source:

  • National Institutes of Health Science Education Partnership Award, 5R25OD010543-02