HOW WE USE HEAT 



Two extremes in clothing. Give scientific reasons for the two conditions in 

 clothing shown here. 



vegetable origin. Rayon is a chemical product made 

 from vegetable matter such as wood pulp and low-grade 

 cotton. 



Demonstration 6. Fibers and Tests for Fibers. 



Physical Appearance of Fibers. Examine under the microscope, 

 slides of wool, cotton, flax, silk, and rayon. Wool fibers have 

 little scales projecting from the surface. Cotton fibers look twisted. 

 Flax fibers are never twisted, vary in size, and have small transverse 

 markings. Silk fibers have no markings, are smaller in diameter 

 than flax. Rayon fibers are smooth like silk but much longer. 

 Place in your workbook sketch drawings showing the appearance 

 of the different fibers. 



Absorption-of-Water Test. Place small equal-sized samples of 

 cloth made of the different fibers in saucers containing equal 

 amounts of water. Which absorbs the most water? Which the 

 least? 



Chemical Test. Boil each of the five different kinds of cloth in 

 a lye solution (5 per cent sodium hydroxide). Wash carefully in 



