3.2 The International System of Units ____ HR/Name _______________________________________ temperature: Celsius scale: Kelvin scale: Reading Assignment: pages 73 - 79 Vocabulary absolute zero: International System of Units (SI): energy: meter (m): liter (L): joule (J): kilogram: gram (g): calorie (cal): weight: 3.2 The International System of Units ____ HR/Name _______________________________________ Metric Prefixes Prefix Meaning Factor mega (M) kilo (k) deci (d) centi (c) milli (m) Quantity SI base unit Symbol Length micro (μ) Mass nano (n) Temperature Time Amount of substance Luminous intensity Units and Quantities Electric current L E N G T H Metric Units of Length Unit relationship kilometer (km) 1. meter (m) base unit decimeter (dm) centimeter (cm) 2. millimeter (mm) micrometer (�m) nanometer (nm) 3. V O L U M E 4. Metric Units of Vol u m e Unit relationship Liter (L) base unit 5. milliliter (mL) microliter (�L) cubic centimeter (cm3) 6. 3.2 The International System of Units ____ HR/Name _______________________________________ equivalent units of temperature, the degree Celsius and the kelvin. M A S S Metric Units of Mass Unit relationship The Celsius scale of the metric system is named kilomgram (kg) base unit after the Swedish astronomer Anders Celsius gram (g) (1701–1744). It uses two readily determined milligram (mg) temperatures as reference temperature values: the freezing point and the boiling point of microgram (�g) water. The Celsius scale sets the freezing point of nanogram (ng) water at 0 oC and the boiling point of water at 100 oC. The distance between these two fixed points is divided into 100 equal intervals, or Temperature degrees Celsius (oC). Temperature is a measure of how hot or cold an Another temperature scale used in the physical obJect is. An obJect’s temperature determines the sciences is the Kelvin, or absolute, scale. This scale direction of heat transfer. When two objects at is named for Lord Kelvin (1824–1907), a Scottish different temperatures are in contact, heat moves physicist and mathematician. On the Kelvin scale, from the obJect at the higher temperature to the the freezing point of water is 273.15 kelvins (K ), obJect at the lower temperature. and the boiling point is 373.15 K. Notice that with the Kelvin scale, the degree sign is not used. Almost all A change of one degree on the Celsius scale is substances equivalent to one kelvin on the Kelvin scale. The expand with an zero point on the Kelvin scale, 0 K, or absolute increase in zero, is equal to -273.15 oC. For problems in this temperature and course, you can round -273.15 oC to -273 oC. contract as the temperature Because one degree on the Celsius scale is decreases. (A very equivalent to one kelvin on the Kelvin scale, important converting from one temperature to another is exception is easy. You simply add or subtract 273, as shown in water.) These the following equations. properties are the basis for the common liquid- in-glass thermometer. The liquid in the Converting Between Temperature Scales thermometer expands and contracts more than Normal human body temperature is 37 oC. What is the volume of the glass, producing changes in the that temperature in kelvins? column height of liquid. Units of Temperature: Kelvin and Celsius Scale Several temperature scales with different units Liquid nitrogen boils at 77.2 K. What is this have been devised. Scientists commonly use two temperature in degrees Celsius? 3.2 The International System of Units ____ HR/Name _______________________________________ The element silver melts at 960.8 oC and boils at 2. Which metric units are commonly used to 2212 oC. Express these temperatures in kelvins. measure length, volume, mass, temperature, and energy? Units of Energy 3. Name the quantity measured by each of the seven SI base units and give the SI symbol of the unit. 4. What is the symbol and meaning of each prefix? This a house equipped with solar panels. The solar a. milli- panels convert the radiant energy from the sun into electrical energy that can be used to heat water and power appliances. Energy is the capacity to do work or to produce heat. b. nano- Like any other quantity, energy can be measured. The Joule and the calorie are common units of energy. The joule (J) is the SI unit of energy. It is c. deci- named after the English physicist James Prescott Joule (1818–1889). One calorie (cal) is the quantity of heat that raises the temperature of 1 g of pure water by 1 oC. Conversions between joules d. centi- and calories can be carried out using the following relationships. 5. List the following units in order from largest to 1 J = 0.2390 cal 1 cal = 4.184 J smallest: m3, mL, cL, μL, L, dL. Homework Questions 1. Which five SI base units are commonly used in 6. What is the volume of a paperback book 21 cm chemistry? tall, 12 cm wide, and 3.5 cm thick? 3.2 The International System of Units ____ HR/Name _______________________________________ 7. State the difference between mass and weight. 8. State the relationship between degrees Celsius and kelvins. 9. Surgical instruments may be sterilized by heating at 170 oC for 1.5 hr. Convert 170 oC to kelvins. 10. State the relationship between joules and calories. 11. Look up the boiling points of the first four elements in Group7A on page R32 of your textbook. Convert these temperatures into kelvins. .