Types of Observations and Measurements We make QUALITATIVE observations – physical and chemical properties and changesWe make QUALITATIVE observations – physical and chemical properties and changes We also make QUANTITATIVE MEASUREMENTS, which involve numbers.We also make QUANTITATIVE MEASUREMENTS, which involve numbers. –Use SI units — based on the metric system

SI measurement Le Système international d'unitésLe Système international d'unités Among countries with non- metric usage, the U.S. and Bahrain are the only countries significantly holding out.Among countries with non- metric usage, the U.S. and Bahrain are the only countries significantly holding out. The U.S. officially adopted SI in 1866.The U.S. officially adopted SI in 1866.

Why should all scientists use the same measurement system/ On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mars’ atmosphere 100 km lower than planned and was destroyed by heat. 1 lb = 1 N 1 lb = 4.45 N

Standards of Measurement When we measure, we use a measuring tool to compare some dimension of an object to a standard. For example, at one time the standard for length was the king’s foot. What are some problems with this standard?

Stating a Measurement In every measurement there is a  Number followed by a  Unit from a measuring device The number should also be as precise as the measurement!

UNITS OF MEASUREMENT Use SI units — based on the metric system LengthMassVolumeTimeTemperature Meter, m Kilogram, kg Seconds, s Celsius degrees, ˚C kelvins, K Liter, L

Mass vs. Weight Mass: Amount of Matter (grams, measured with a BALANCE)Mass: Amount of Matter (grams, measured with a BALANCE) Weight: Force exerted by gravity (Newton, measured with a SPRING SCALE)Weight: Force exerted by gravity (Newton, measured with a SPRING SCALE) I weigh 0 N right now

Some Tools for Measurement Fluid Volume – Graduated Cylinder and Beaker Volume – Ruler/Calculator Time – Stopwatch or Clock Mass – Balance Weight – Spring Scale Temperature – Thermometer

Learning Check Match L) length M) mass V) volume ____ A. A bag of tomatoes is 4.6 kg. ____ B. A person is 2.0 m tall. ____ C. A medication contains 0.50 g Aspirin. ____ D. A bottle contains 1.5 L of water. M L M V

Metric Prefixes

m = 1 ___a) mm b) km c) dm g = 1 ___ a) mg b) kg c) dg L = 1 ___a) mL b) cL c) dL m = 1 ___ a) mm b) cm c) dm Learning Check

Select the unit you would use to measure 1. Your height a) millimeters b) meters c) kilometers 2. Your mass a) milligramsb) grams c) kilograms 3. The distance between two cities a) millimetersb) meters c) kilometers 4. The width of an artery a) millimetersb) meters c) kilometers

Temperature Scales FahrenheitFahrenheit CelsiusCelsius KelvinKelvin Anders Celsius Lord Kelvin (William Thomson)

Temperature Scales 1 kelvin = 1 degree Celsius Notice that 1 kelvin = 1 degree Celsius Boiling point of water Freezing point of water Celsius 100 ˚C 0 ˚C 100˚C Kelvin 373 K 273 K 100 K Fahrenheit 32 ˚F 212 ˚F 180˚F

Calculations Using Temperature Generally require temp’s in kelvinsGenerally require temp’s in kelvins T (K) = t (˚C) T (K) = t (˚C) Body temp = 37 ˚C = 310 KBody temp = 37 ˚C = 310 K Liquid nitrogen = -196 ˚C = 77 KLiquid nitrogen = -196 ˚C = 77 K Generally require temp’s in kelvinsGenerally require temp’s in kelvins T (K) = t (˚C) T (K) = t (˚C) Body temp = 37 ˚C = 310 KBody temp = 37 ˚C = 310 K Liquid nitrogen = -196 ˚C = 77 KLiquid nitrogen = -196 ˚C = 77 K

Reading a Meterstick. l I.... I 3....I.... I 4.. cm First digit (known)= 2 2.?? cm Second digit (known)= ? cm Third digit (estimated) between Length reported=2.75 cm or2.74 cm or2.74 cm or2.76 cm

Learning Check. l I.... I 9....I.... I 10.. cm What is the length of the line? 1) 9.6 cm 2) 9.62 cm 3) 9.63 cm

Fluid Volume Meniscus – curved area at top of fluid, caused by surface tension –Read bottom of the curve to get an accurate measurement

Learning Check

Volume of a Regular Solid Volume = Length x Width x Height

Volume Displacement Measure volume in mL before adding object. Gently slide object into cylinder and re-measure the volume. Gently slide object into cylinder and re-measure the volume. Subtract the smaller number from the larger number. Subtract the smaller number from the larger number. 33 mL 25 mL

Triple Beam Balance Measurements are in grams grams

DENSITY - an important and useful physical property Mercury 13.6 g/cm g/cm 3 Aluminum 2.7 g/cm 3 Platinum

DENSITYDENSITY Density is an INTENSIVE property of matter.Density is an INTENSIVE property of matter. –does NOT depend on quantity of matter. –temperature Contrast with EXTENSIVEContrast with EXTENSIVE –depends on quantity of matter. –mass and volume. Styrofoam Brick