Chapter 4

Measurement

Monday• Accuracy, precision, dimensional analysis• Foldable on Metric System

TEK to be covered• 2 (F) collect and organize qualitative and quantitative data

and make measurements with accuracy and precision using tools and equipment;

Units of Measurement

Before 1795, measurement units were inexact!!!!

Units of Measurement

• In 1960 the metric system was updated and is called the Systeme Internationale d’Unites or the SI unit of measurement.• Standard units of measurement for

ALL scientists to use worldwide.

•Base Unit - unit of measurement based on an object or event in the physical world

The standard kilogram is stored in a vault at the International Bureau of Weights and Standards near Paris. It is made of a platinum-iridium alloy, and is shown here next to an inch-based ruler for scale.

• Base Units:2. Time: second (s)

3. Length: meter (m)

4. Mass: kilogram (kg)

•Derived Unit - A unit that is a combination of base units.•There are hundreds of units needed for measuring “everything,” but they are all derived from those base units.

1. Volume = L x W x H for a regularly shaped solidcubic meter (m3),cubic centimeter (cm3) or cubic decimeter (dm3)

Unit for volume: liter (L) for a liquid 1 dm3 = 1 L 1 cm3 = 1 mL

How reliable are measurements?

•Accuracy – how close a measured value is to an accepted value•Precision – how close a series of measurements are to each other•Compare to throwing darts bottom of pg 36.

ACCURACY VS. PRECISION:

HOWEVER, if the actual time is 3:00, then the second clock is more accurate than the first one.

• ACCURACY = HOW CLOSE A MEASUREMENT IS TO THE TRUE VALUE• PRECISION = EXACTNESS

THIS CLOCK is more precise than THIS CLOCK

Metric Units

• The metric system is based on the decimal system, in which numbers are expressed in units of ten.

Metric Mnemonic

• King• Henry• Died • Monday• Drinking • Chocolate • Milk

• Kilo• Hecto• Deca• Base unit• Deci• Centi• milli

Measuring Length• When measuring length, use a metric ruler or meter stick. • Millimeters arte generally the smallest divisions represented

Measuring Volume

• Liquids are best measured using a graduated cylinder• Cooks use:• Measuring spoons and

measuring cups

Measuring temperature• Temperature is

measured in degrees Celcius in the metric system• To ensure accurate

measurement of temperature, ensure that the bulb is completely immersed in the container

Measurement Equivalence for Solids1 tablespoon (tbsp) = 3 teaspoons (tsp)1/16 cup (c) = 1 tablespoon1/8 cup = 2 tablespoons1/6 cup = 2 tablespoons + 2 teaspoons1/4 cup = 4 tablespoons1/3 cup = 5 tablespoons + 1 teaspoon3/8 cup = 6 tablespoons1/2 cup = 8 tablespoons2/3 cup = 10 tablespoons + 2 teaspoons3/4 cup = 12 tablespoons1 cup = 48 teaspoons1 cup= 16 tablespoons

Measurement Equivalence for Liquids

• 8 fluid ounces (fl oz) = 1 cup1 pint (pt) = 2 cups1 quart (qt) = 2 pints4 cups = 1 quart1 gallon (gal) = 4 quarts16 ounces (oz) = 1 pound (lb) 1 milliliter (ml) = 1 cubic centimeter (cc)

Tuesday• Measurement Lab

Worksheet• Practice over metric conversion

Thursday• Review worksheet

Friday• Test over the metric system• Start notes on classification of matter• pure substance and a mixture: homogenous and

heterogenous mixtures (using a venn diagram), solutions, colloids

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