Presentation on theme: "Chapter 1 The Nature of Science"— Presentation transcript:
1 Chapter 1 The Nature of Science Cubit: span from tip of middle finger to the elbow. Measure your seatmate’s height in cubits. Or measure back table length in cubits. Record measurements. How do they compare?
2 Standards of Measurement Accurate measurement is needed in a valid experiment.Standard—an exact quantity that people agree to use for comparison.In order for a measurement to make sense, it must include a number AND a unit.Examples: 150 ft, 35 cm, 64 mi
3 Measurement SystemsUS: English system (pounds, feet, inches, Fahrenheit)Most other nations: metric systemScience Worldwide: an improved version of the metric system called “International System of Units” or SI units.SI comes from the French Le Systeme Internationale d’UnitesIt is easier to convert units and share with others around the world.
4 The SI System SI Measurements and Base units Base unit for length is the meter (m)Converted unit: centimeter, kilometerBase unit for mass is the kilogram (kg)Converted unit: gram, milligramBase unit for time is the second (s)Converted unit: microsecondBase unit for electric current is the ampere (amp)Base unit for temperature is the kelvin (K)Base unit for volume is the liter (L)
5 The SI System Something Called SI The SI system is based on the number 10.Prefixes are used with the names of the units to indicate multiples of 10.Prefix multiplying factorkilo = 1000 (thousand)deci = 1/10 or 0.1 (tenth)centi = 1/100 or 0.01 (hundredth)milli = 1/1000 or (thousandth)micro = 1/1,000,000 or (millionth)nano = 1/1,000,000,000 or (billionth)Something Called SI
6 Derived Units Derived Unit: a unit that combines different SI units Common Derived Units:Area: cm2 or m2Volume: cm3 or m3Density: g/mL or g/cm3
9 What is density? It is a derived unit. Density= mass divided by volume.How do you determine mass? Use a balance.Measure in grams or kilograms.Mr. Edmonds Rock to an Oldie
10 How do you determine volume? We will express volume in cm3 and mL.For a rectangular prism, V= L x W x HFor a liquid, measure volume using a graduated cylinder.Find density first 90 seconds approximately no sig figsBase units Meters Liters and Grams focus on litersFor a cube, volume = side cubed. For a sphere, volume = 4/3 pi x radius cubed. For a cylinder, volume is pi r squared x height.
11 Density=mass volume Because 1 cm3 = 1 mL Density=m (grams) = m (g) V (cm3) v (mL)Example:D=62.4 g/ (8.5 cm x 2.5 cm x 3.3cm)=D=62.4 g/ 70.1 cm3 = .9 g/ cm3Wood floats in water because it has a lower density. An anchor sinks because the metal has a higher density than water. Helium balloons float because the density of the helium is lower than the density of the air. When the gas station tests the antifreeze in your car, they siphon some into a hydrometer. The hydrometer has objects in it that float in the liquid. By observing which objects float, it can be determined what the density of the liquid is, and if the chemicals are strong enough to retain the necessary freezing point.
12 Accurate Measurement Readings Read to the nearest mark, then estimate the number one decimal place further.49.6 can be read with the lines on the rulerEstimate the last digit4.4 can be readEstimate the last digit6.1 can be read with the linesEstimate the last digit49.66 cm47.1 can be read with the lines on the rulerEstimate the last digit47.10 cm
13 Dimensional AnalysisSometimes things need to be converted to different units.You can use a conversion factor (a ratio) to change one unit to another.Ex. 1 in = 2.54 cmThis process is called dimensional analysis
14 Conversion Process 5 Steps of Dimensional Analysis Start with the given (number & unit)X (times)Write the conversion factor as a fraction with the given unit on the bottom and new unit on topCross out units that cancelCalculate & write the correct answer & units
15 Example: How many centimeters is 6.74 in? Start with the given (number & unit)X (times)Write the conversion factor as a fraction with the given unit on the bottom and new unit on top in = 2.54 cmCross out units that cancelCalculate & write the correct answer & units2.54 cm6.74 inX= cm1 in
17 How many jumps does it take? Ladder Method12KILO 1000 k3HECTO 100 hDEKA 10 daDECI 0.1 dMeters Liters GramssecondsCENTI 0.01 cMILLI mHow do you use the “ladder” method?1 – Determine your starting point.2 – Count the “jumps” to your ending point.3 – Move the decimal the same number of jumps in the same direction.4 km = ________mStarting PointEnding PointHow many jumps does it take?4.1__.2__.3__.= 4000 m