Scientific UnitsScientific Units

1.2 Notes Part B1.2 Notes Part B

Unit ObjectivesUnit Objectives

Use appropriate SI units for length, Use appropriate SI units for length, mass, time, temperature, quantity, mass, time, temperature, quantity, area, volume and density. (ACT area, volume and density. (ACT Quality Core I.A.2.b)Quality Core I.A.2.b)

SI UnitsSI Units

Le Système International d’Unités Le Système International d’Unités (SI)(SI)

International System of Units in USAInternational System of Units in USA

A modern version of the metric A modern version of the metric system based on a decimal systemsystem based on a decimal system Understood throughout the worldUnderstood throughout the world Each type of measurement has a base Each type of measurement has a base

unitunit Multiples of 10Multiples of 10

LengthLength

Distance between 2 pointsDistance between 2 points SI base unit = meter (m).SI base unit = meter (m). Metric rulers and meter sticks are Metric rulers and meter sticks are

used to measure lengthused to measure length

MassMass

The quantity of matter in an objectThe quantity of matter in an object SI Base Unit = gram (g)SI Base Unit = gram (g) NOT the same as weightNOT the same as weight

Weight = Newton (N) = measure of Weight = Newton (N) = measure of gravitational force on an objectgravitational force on an object

VolumeVolume

The amount of space occupied by an The amount of space occupied by an objectobject Can measure volume of a solid, liquid, Can measure volume of a solid, liquid,

or gasor gas SI base unit is the liter, LSI base unit is the liter, L

A liter occupies the same volume as a A liter occupies the same volume as a cubic decimeter, dm3. cubic decimeter, dm3.

1 L = 1 dm31 L = 1 dm3 (1 mL = 1 cm3)(1 mL = 1 cm3)

Measuring VolumeMeasuring Volume

FOR SolidsFOR Solids Measure length, width, and height Measure length, width, and height

Multiply the three numbers and their Multiply the three numbers and their units together (V = l x w x h)units together (V = l x w x h)

Volume = expressed in cubic Volume = expressed in cubic centimeters, cm3centimeters, cm3

SI UnitsSI Units

Time = second (s) = interval Time = second (s) = interval between 2 eventsbetween 2 events

Temperature = Kelvin (K) = measure Temperature = Kelvin (K) = measure of the average kinetic energy of of the average kinetic energy of particles in an objectparticles in an object Kelvin = °C +273Kelvin = °C +273 °C = Kelvin - 273°C = Kelvin - 273

Example: 20 °C + 273 = 293 KExample: 20 °C + 273 = 293 K

TimeTime

Time is the interval between two Time is the interval between two events.events. Or the time it takes for something to Or the time it takes for something to

happenhappen SI unit for time = second (s)SI unit for time = second (s)

TemperatureTemperature

Measure of how hot or how cold Measure of how hot or how cold something is.something is.

For most scientific work, temperature For most scientific work, temperature is measured on the Celsius (C) scale.is measured on the Celsius (C) scale. On this scale, the freezing point of water On this scale, the freezing point of water

is 0is 0C, and the boiling point of water is C, and the boiling point of water is 100100C.C.

Between these points, the scale is divided Between these points, the scale is divided into 100 equal divisions. Each one into 100 equal divisions. Each one represents 1represents 1C.C.

TemperatureTemperature

SI Unit = Kelvin (K).SI Unit = Kelvin (K). Absolute Zero (0K) = coldest possible Absolute Zero (0K) = coldest possible

temperaturetemperature Absolute zero is equal to -273Absolute zero is equal to -273C which is C which is

273273 below the freezing point of water. below the freezing point of water.

Finding KelvinFinding Kelvin

Kelvin temperature can be found by Kelvin temperature can be found by adding 273 to the Celsius reading. adding 273 to the Celsius reading.

On the Kelvin scale, water freezes at On the Kelvin scale, water freezes at 273 K and boils at 373 K.273 K and boils at 373 K. To find Kelvin simply add 273 to the °CTo find Kelvin simply add 273 to the °C

K = °C +273K = °C +273 To find Celsius, subtract 273 from the KTo find Celsius, subtract 273 from the K

°C = Kelvin - 273°C = Kelvin - 273

TemperatureTemperature

These three thermometers illustrate These three thermometers illustrate the scales of temperature between the scales of temperature between the freezing and boiling points of the freezing and boiling points of water.water.

DensityDensity

Density is the mass per unit volume Density is the mass per unit volume of a materialof a material

You find density by dividing an You find density by dividing an object’s mass by the object’s volumeobject’s mass by the object’s volume

Density = Derived UnitDensity = Derived Unit

SI Unit = g/cm3 SI Unit = g/cm3 A combination of SI units.A combination of SI units.

A unit obtained by combining A unit obtained by combining different SI units or multiply an IS different SI units or multiply an IS unit by itself = a derived unit. unit by itself = a derived unit.

SI UnitsSI Units

Length = metersLength = meters Mass = gramsMass = grams Time = secondsTime = seconds Temperature = KelvinTemperature = Kelvin Volume = Liters, cubic centimetersVolume = Liters, cubic centimeters Density = g/mL, g/cm3Density = g/mL, g/cm3

In-Class Assignment/HomeworkIn-Class Assignment/Homework

Page 879 #1-4, 6-10 Math Page 879 #1-4, 6-10 Math ProblemsProblems 1 m = 10 dm =100 cm = 1000 mm1 m = 10 dm =100 cm = 1000 mm 1 dm = 10 cm = 100 mm1 dm = 10 cm = 100 mm 1 cm = 10 mm1 cm = 10 mm 1 L = 1 dm1 L = 1 dm33

1 mL = 1 cm1 mL = 1 cm33

1.2 reinforcement WKT1.2 reinforcement WKT