3. Materials Around Us

All the things around us consist of one or more materials, such as glass, metal, plastics, wood, cotton, paper, mud, and soil, etc.

Now, let's examine the various objects and the materials from which they are constructed.

Some materials are used to make different types of objects. Let us look at a few examples.

Fig. 3.2 Materials around us

We have lots of different materials around us, and we often have to decide which ones to use. Each material has its own advantages and disadvantages. We can figure them out by using our senses, observing, experimenting, or testing. 

Knowing about material properties also helps us make smart choices. 

For instance, if you were building a house in really cold places like Antarctica, you'd want materials that trap heat inside to keep you warm. But if you were making a house in a tropical area with hurricanes and floods, you'd need materials that stay strong even when they get wet. So, understanding material properties helps us pick the best materials for the job.

Let us understand how materials are selected for making different objects, based on the intended purpose of the object and the specific properties of the material2: 

• Wood Spears:
  They use spears for hunting and fishing. The spears need to be durable, strong, flexible and lightweight.
  They use lightweight bamboo for fishing spears because it's easier to get them back from the water since they float.
  For hunting spears, they use two types of wood: light and flexible wood for the long part of the spear, and heavy wood for the spear head.

Fig. 3.6 Wood spears 

• Wood Canoes and Shelters:  
  To bend wood, they use steam. They do this when building dome-shaped shelters. Also, they use steam to shape sheets of stringybark over a fire when making canoes. Stringybark is used as a canvas for their art. They made it flexible by heating it over a fire, so it could be flattened for painting and creating artwork.

Fig. 3.7 Wood canoes

• Water Carriers:
  Water carriers need to be waterproof. They use wallaby skins to create water carriers. First, they dry the skins, and then they treat them with resin. This not only makes the material last longer but also makes it waterproof, so it can carry water without leaking.

Fig. 3.8 Wallaby skin water carrier

• Clothing:
  Clothing for cold and wet weather has two important jobs: keeping people warm and dry. To stay warm, it needs to have good insulation. To stay dry, it should be water-resistant or not soak up water easily.

When it's raining, people wear animal fur with the furry side facing outward. This helps protect them from getting wet because the skin side would get wet much faster. But when the weather is cool and dry, they wear possum fur with the furry side facing inward. This way, the warm air gets trapped between the hairs, keeping them cozy.