Part 15 of Chapter1 in Chemistry

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The book moves into Heat Measurements stating that" The scales previously discussed are used to measure the degree of heat, A pail of water and a thimble full of water can both be filled with water at" 100degreeC. "They both have the same measurement of the degree of heat of the water. However, the pail of water has a greater quantity of heat. This can be easily demonstrated by the amount of ice that can be melted by the water in these two containers. Obviously, the pail of water at 100degree C will melt more ice than a thimble full of water at the same temperature. We say that the pail of water contains a greater number of calories (cal) of heat. The calorie unit is used to measure the quantity of heat. It is defined as the amount of heat needed to raise the temperature of 1 g of water by 1 degree on the Celsius scale. This is a rather small unit for the quantities of heat that are involved in most chemical reactions. Therefore, the kilocalorie (kcal) is more often used. The kilocalorie is equal to 1000 cal. It is the quantity of heat that will increase temperature of 1kg of water by 1 degree on the Celsius scale. As a unit of heat energy, 1 cal is approximately 4.18J(the joule-a derived unit in the SI system equal to a kilogram meter squared per second squared (kg x m to the 2/s to the 2). Since this unit is fairly small, changes in energy associated with chemical reactions are often expressed in kilojoules(kJ). "Problems involving heat transfers in water are called water calorimetry problems" explained on page 167. Scientific Notation " When students must do mathematical operations with numerical figures, the 'scientific notation' system is very useful. Basically, this system uses the exponential means of expressing figures. With large numbers, such as 3,630,000, move the decimal point the left until only 1 digit remains to the left (3,630000) and then indicate the number of moves of the decimal point as the exponent of 10 giving you 3.63 x 10 to the sixth. With a very small number such as 0.000000123, move the decimal point to the right until only one digit is to the left 0000001.23 and then express the number of moves as the negative exponent of 10 giving you 1.23 x 10 to the -7. Remember the first factor in scientific notation must have only one digit to the left of the decimal and it must not be 0.