Measurement

Measure the following without using any measuring tool.

a. height of the doorb. width of the roomc. thickness of chemistry bookd. weight of pilot ballpene. mass of board marker

What is SI System of

units?

SI System of Units

also known as Systeme International d’Unites

a modified form of the metric system and is generally a system of units of measurement

simple and convenient to use since all units are based on multiples of 10.

What is the SI unit for:Length? Mass?

Temperature? Time?

Amount of substance? Luminous intensity?

Volume?

Quantity Name of Unit Symbol

Length meter m

Mass kilogram kg

Time second s

Electrical current ampere A

Volume cubic meter  m3

Thermodynamic temperature Kelvin K

Luminous intensity candela cd

Amount of substance mole mol

Multiplier Prefix Symbol

1018 exa E1015 peta P1012 tera T109 giga G106 *mega M103 *kilo k102 hecto h101 deka da10-1 deci d10-2 *centi c10-3 *milli m10-6 *micro μ10-9 nano n10-12 pico p10-15 femto f10-18 atto a

Prefixes Symbol Factor

yotta Y 1024 = 1,000,000,000,000,000,000,000,000

zetta Z 1021 = 1,000,000,000,000,000,000,000

exa E 1018 = 1,000,000,000,000,000,000

peta P 1015 = 1,000,000,000,000,000

tera T 1012 = 1,000,000,000,000

giga G 109 = 1,000,000,000

mega M 106 = 1,000,000kilo k 103 = 1,000

hecto h 102 = 100deka da 101 = 10deci d 10-1 = 0.1centi c 10-2 = 0.01milli m 10-3 = 0.001micro µ 10-6 = 0.000,001

nano n 10-9 = 0.000,000,001

pico p 10-12 = 0,000,000,000,001

femto f 10-15 = 0.000,000,000,000,001

atto a 10-18 = 0.000,000,000,000,000,001

zepto z 10-21 = 0.000,000,000,000,000,000,001

yocto y 10-24 = 0.000,000,000,000,000,000,000,001

Formula - Temperature:

°C= 5/9 (°F-32)

°F=9/5 (°C+32)

K= °C + 273

°C= K-273

What is the importance of

having standard units of

measurement?

Synthesizing

Self-check: Give examples of transactions or activities in our country

which make use of metric system.

Mass (g) Volume (L)

Length (m)

Time (s)

Accuracy and

Precision

Precision is the degree of agreement between different values obtained under basically the same conditions; it is a measure of the degree with which measurements agree; is how close the measured values are to each other.

Accuracy is the degree of agreement between the experimental result and the true value; is how close a measured value is to the actual (true) value.

Trials Group A Group B Group C

1 0.980 g/mL 0.732 g/mL 1.023 g/mL

2 1.020 g/mL 0.731 g/mL 0.739 g/mL

3 0.970 g/mL 0.733 g/mL 0.845 g/mL

Average 0.990 g/mL 0.732 g/mL 0.869 g/mL

True Value=1.000 g/mL

Examples of Precision and Accuracy:

Low Accuracy

High Precision

High Accuracy

Low Precision

High Accuracy

High Precision

Factors affecting accuracy and precision

∞Human error∞Condition of equipment∞Quality of materials used∞Environmental conditions

such as temperature and pressure

Complete the given speculation about effect journal regarding measurement:

What happened? What could happen because of this?

1. Balance not pointing to zero

2. Glassware used is dirty

3. Inconsistency in techniques used by the experimenter

4. Undetermined purity of the reagents

5. Position of the experimenter in reading the measuring scale