Week 21 - Machines Help Us Do Work

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Lesson 3

Read pages 258 to 260 and 315 to 320

Prehistoric men and women spent most of their waking hours hunting and foraging food. They had little choice since bacteria and moulds would quickly attack and spoil their food. This was especially true in warmer climates. Throughout human history, different techniques and technologies have been developed to preserve food. The earliest forms of food preservation where smoking, drying, salting, fermenting, freezing, and pickling. Today, modern refrigerators and freezers are the primary methods of storing and preserving food. In this activity, you will trace the history of food preservation and, in particular, will trace the history of the modern day refrigerator.

Modern day refrigerators slow the growth of bacteria and fungi which helps to preserve food for long periods of time.

  Exercise 1.3: Refrigeration