3.2 The International System of Units HR/Name. temperature: Celsius scale: Kelvin scale: Vocabulary. absolute zero:

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1 temperature: Celsius scale: Kelvin scale: Reading Assignment: pages Vocabulary International System of s (SI): absolute zero: meter (m): energy: liter (L): joule (J): kilogram: gram (g): calorie (cal): weight:

2 Metric Prefixes Prefix Meaning Factor mega (M) kilo (k) deci (d) centi (c) Quantity SI Symbol Length Mass Temperature Time Amount of substance Luminous intensity Electric current milli (m) micro (μ) nano (n) kilometer (km) meter (m) decimeter (dm) centimeter (cm) millimeter (mm) micrometer (μm) nanometer (nm) s and Quantities L E N G T H Metric s of Length Liter (L) milliliter (ml) microliter (μl) V O L U M E Metric s of Vol ume 6. cubic centimeter (cm 3 )

3 equivalent units of temperature, the degree Celsius and the kelvin. M A S S kilomgram (kg) gram (g) milligram (mg) microgram (μg) nanogram (ng) Metric s of Mass Temperature Temperature is a measure of how hot or cold an object is. An object s temperature determines the direction of heat transfer. When two objects at different temperatures are in contact, heat moves from the object at the higher temperature to the object at the lower temperature. Almost all substances expand with an increase in temperature and contract as the temperature decreases. (A very important exception is water.) These properties are the basis for the common liquid- in- glass thermometer. The liquid in the thermometer expands and contracts more than the volume of the glass, producing changes in the column height of liquid. The Celsius scale of the metric system is named after the Swedish astronomer Anders Celsius ( ). It uses two readily determined temperatures as reference temperature values: the freezing point and the boiling point of water. The Celsius scale sets the freezing point of water at 0 o C and the boiling point of water at 100 o C. The distance between these two fixed points is divided into 100 equal intervals, or degrees Celsius ( o C). Another temperature scale used in the physical sciences is the Kelvin, or absolute, scale. This scale is named for Lord Kelvin ( ), a Scottish physicist and mathematician. On the Kelvin scale, the freezing point of water is kelvins (K ), and the boiling point is K. Notice that with the Kelvin scale, the degree sign is not used. A change of one degree on the Celsius scale is equivalent to one kelvin on the Kelvin scale. The zero point on the Kelvin scale, 0 K, or absolute zero, is equal to o C. For problems in this course, you can round o C to o C. Because one degree on the Celsius scale is equivalent to one kelvin on the Kelvin scale, converting from one temperature to another is easy. You simply add or subtract 273, as shown in the following equations. Converting Between Temperature Scales Normal human body temperature is 37 o C. What is that temperature in kelvins? s of Temperature: Kelvin and Celsius Scale Several temperature scales with different units have been devised. Scientists commonly use two Liquid nitrogen boils at 77.2 K. What is this temperature in degrees Celsius?

4 The element silver melts at o C and boils at 2212 o C. Express these temperatures in kelvins. 2. Which metric units are commonly used to measure length, volume, mass, temperature, and energy? s of Energy 3. Name the quantity measured by each of the seven SI s 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 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. 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 named after the English physicist James Prescott Joule ( ). One calorie (cal) is the quantity of heat that raises the temperature of 1 g of pure water by 1 o C. Conversions between joules and calories can be carried out using the following s. 1 J = cal 1 cal = J a. milli- b. nano- c. deci- d. centi- 5. List the following units in order from largest to smallest: m 3, ml, cl, μl, L, dl. Homework Questions 1. Which five SI s are commonly used in chemistry? 6. What is the volume of a paperback book 21 cm tall, 12 cm wide, and 3.5 cm thick?

5 7. State the difference between mass and weight. 8. State the between degrees Celsius and kelvins. 9. Surgical instruments may be sterilized by heating at 170 o C for 1.5 hr. Convert 170 o C to kelvins. 10. State the 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.