Nt1310 Unit 3 Maths

Units of Measurement: Sections 1.4-1.5

Physical Quality Name of Unit Abbreviation
Mass Kilogram Kg
Length Meter m
Time Second sª (Sec)
Temperature Kelvin K
Amount of Substance Mole mol

• Système International d’Unitès (used in the science community world wide)
• Uses different base unit for quantity

Velocity m/s (two base units build velocity = derived unit) {g/sec, kg/min}

Metric System

Prefix Abbreviation Meaning
Mega M 106
Kilo k 103
Centi c 10-2
Milli m 10-3
Micro µ 10-6
Nano n 10-9
Pico p 10-12

Volume

Most common used metric u nits for volume: Liter (L), milliliter (mL),
1dm3 = 1L A liter is a cube 1 dm long on each side
1cm3 = 1mL
A milliliter is a cube 1 cm long on each side

Uncertainty in Measurements

Different measuring devices have different uses and degrees of accuracy. Some examples are of these devices are:

• Graduated Cylinders
• Syringe
• Buret
• Pipet
• Volumetric Flask

Temperature

Measure of average kinetic energy of particles in a sample
• Kelvic Scale (purely scientific)
• Celsius Scale (scientific)
• Farenheit Scale (U.S. Only)

Molecules and atoms become unstable at Absolute zero.
No negative temperatures of Kelvins
Celsius scale is based on properties of water
0° is the freezing point of water

The Kelvin is the SI unit of temperature.
It is based on the properties of gases

K + °C + 273.15

The farenheit scale is not used in scientific measurements
°F = 1.8(°C) + 32
°C = 0.56 (°F-32)

Density

• Physical property of a substance d = m/v [g/mL, kg/L, kg/m3, g/cm3]
• The formula for density is Mass per unit volume d = m/v

Significant Figures

• Digits that were measured (sig figs)
• When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers.
• All nonzero digits are significant
• Zeros between two significant figures are themselves sgnigicant
• Zeros at the beginning of a number are never significant
• Zeros at the end of a number are significant if a decimal point is written in the number.
#’s 100 1746 2201 6.250 0.009340 90301 0.0902 130.059 50 160
Sig. Fig 1 4 4 4 4 5 3 6 1 2

When addition or subtraction is performed, answers are rounded to the least significant decimal place.

20.4 (1) 16.964 (4)
- 1.322 (3) - 8.0693
__________ ___________ 19.122 8.8953 19.1 8.895

When multiplication and division is performed answers are rounded to the number of digits that corresponds to the least number of sig. figs in any of the numbers used in the calculation.

6.221 (4) 8.98765 (6) 12.64 (4) x 5.2 (2) x 6.1 (2) x 10 (1)
_________ ___________ _________ 32.3492 54.824665 126.40 32 55 100

Accuracy vs. Precision

Accuracy I show close you are to an expected result
Precision is how often you repeat the same results

Exponential
Numbers

1. Consists of a coefficient (whole number) that are less than 10 and greater than 1.
2. Also consists of a power of ten (10x)
• When you move your decimal to the left to obtain your coefficient the exponent is positive.
• When you move your decimal to the right to obtain your coefficient the exponent is negative.

Example: 1.784 0.00654 1.784x 103 6.54 x 10-3