How much of the air supports burning? PAGE Is air a mixture? How can we explain burning? - What is a flame? - Why do some substances char? What is formed when carbon burns? How can we make carbon dioxide? What is carbon dioxide like? Why does soda water Fresh air and tuberculosis. - How do we ventilate our houses? How can we ventilate our bedrooms? How to ventilate the schoolroom. Do we need moisture in How do we heat the house? Fireplaces. How does a fire warm us? - Hot-air furnaces. Are heat and temperature the same? measured? - Is heat needed to melt ice? What is the weather? Of what is the atmosphere com- posed? What causes dew and frost? - How are clouds - What is the earth like? What is the sky? Why do the heavenly bodies rise and set? What is the path of a body have weight? In what direction does the earth pull? Why does a body float? What is the density of water? center? Why do planets revolve around the sun? --- Can water be changed? What is an element? How can - - What is formed when hydrogen burns? Do our fuels contain water boil? How is ice made? How is ice cream frozen? Why do we need so much water? How do cities get their water? -- How do we get water in the country? What is plumbing? - What is a pump? What is a force pump? What are the dangers in water? get pure drinking water? What is a filter? What is the earth's crust? What are the classes of rocks? - How are stratified rocks formed? weathering? How is our soil formed? What is the structure of soil? - Why must soil be tilled? What is - PAGE is iron found? How is iron prepared? - How is lead obtained? How is copper obtained? How are gold and silver found? - What is 22-carat gold? men find precious stones? What is coal? What are 178 What makes a compound an acid? How can we test for bases and acids? How does an What are the materials of clothing? - How are silk and Exercises. - What are salting How do we can and preserve foods? preserve food? - How is meat smoked? are the principles of canning? What are the methods of canning? industry. Exercises. |