1st Year BSMT
MeasurementS
in
CHEMISTRY
Prepared by:
WINNELIE KRIS CEA-TEDERA, RMT
Objectives
At the end of the activity, the students must be able to:
1. Express measurement in
various units
Physical Quantities
Height, volume, temperature, and other physical properties that can be
measured are called physical quantities and are described by both a number
and a unit of defined sized.
6.12 kilograms
Unit a defined quantity used as a standard of measurement.
International System of Units abbreviated by SI units.
A system of standard units.
Some SI and METRIC Units and their Equivalents
Quantity
SI unit
Metric Unit
Equivalents
Mass
Kilogram
Gram
1kg = 1000 g
=2.205 lb
Length(Vol)
Meter
Cubicmeter(m3)
Meter
Liter (L)
1m=3.280 ft
=1000L
=264.2gal
Temperature
Kelvin
Celcius degree
Time
Second
(s)
Second
(s)
-----
Volume
Volume
Is the amount of space occupied by an object. The volume of a liquid, solid or gas
is the space occupied by that substance. The basic unit of volume in the metric
system is the liter (L). This unit is a little larger than a quart. The only other
common metric unit for volume is the milliter (mL).
1 =(
1
1000
1 mL = 1 cc
) = 1L
VOLUME MEASUREMENT
PROPER READING
OF VOLUME ON A
GRADUATED
CYLINDER
a "lensshaped".
Calculation of Percent Error
Volume by graduated cylinder – volume using Erlenmeyer Flask or beaker
Volume by graduated cylinder
x100
finds the relative error between the true value and the observed value found
in a measurement.
Which piece of glassware will give you a more accurate measurement of
liquid: the graduated cylinder, the Erlenmeyer flask, or the beaker?
MASS MEASUREMENT
The terms “mass” and “weight” though often use
interchangeably, really have quite different meanings.
Mass is a measure of the amount of matter in an object.
Weight is a measure of the gravitational force that the earth or other
large body exerts on an object.
Density
Mass per unit volume (d=m/v)
At a given temperature, density of a matter is a physical property that is constant
Specific Gravity
Comparison of the density of a given substance with the density of a
given substance will the density of water. Numerically same with density
but no units.
Specific gravity =
(g/mL)
Density of substance
Density of water at the
same temperature (g/mL)
LENGTH
MASS
VOLUME
1 inch-2.54cm
1 0z = 28.35 g
1 qt = 0.946 L
1 meter =39.37 inch
1lb = 453.6 g
1 gal = 3.785 L
1 mile = 1.609km
1 kg = 2.205 lb
1 L = 33.81 fl oz
1 g = 15.43 grains
1 fl oz=29.57
1L =1.057 qt
Mass Measurement
Is the quantity of matter in an object. The base unit of mass in the metric syste
System is the gram (g). As always in the metric system, larger and smaller uni
are indicated by prefixes.
Temperature Measurement
Temperature is a measure of the amount
of heat energy possessed by an object. There are three main
scales commonly used in the world today to measure
temperature: the Fahrenheit (°F) scale, the Celsius (°C) scale, and
the Kelvin (K) scale.
From
to Fahrenheit
to Celsius
to Kelvin
ºF
F
(ºF - 32)*0.5556
(ºF-32)*5/9+273.15
ºC
(ºC * 5/9) + 32
C
ºC + 273.15
K
(K-273.15)*9/5+32
K - 273.15
K
Example: Convert 25° Celsius to Fahrenheit
First: 25° * 1.8 = 45
Then: 45 + 32 = 77° F
Example: Convert 98.6° Fahrenheit to Celsius
First: 98.6° − 32 = 66.6
Then: 66.6 *0.5556= 37° C
Digital thermometers
Digital thermometers are quick to use, reasonably accurate and can be used under the armpit
(always use the thermometer under the armpit with children under 5). Hold your child's arm
gently against their body and leave the thermometer in place for the time stated in the
manufacturer's instructions.
Ear (or tympanic) thermometers
Ear thermometers are put in the child's ear. They take the child's temperature in one second
and do not disturb the child, but they're expensive and the reading may not be accurate if the
thermometer is not correctly placed in the ear. So read the manufacturer's instructions
carefully to find out how to place the thermometer in the ear and how long the reading will
take.
Infrared thermometers
These use an infrared scanner to measure temperature.
Strip-type thermometers
Strip-type thermometers, which you hold on your child's
forehead, are not an accurate way of taking their temperature.
Mercury thermometers
Do not use mercury thermometers. Mercury-in-glass
thermometers haven't been used in hospitals for some years and
are no longer available to buy. They can break, releasing small
shards of glass and highly poisonous mercury.
Time
Is the one quantity for which the units are the same in all
systems: English, metric, and S.I. The base unit is the second
(s).
60s
60min
=
=
1 min
1h
ACCURACY VS PRECISION
correctness of a result, freedom from error, or how close the answer to the
true value
measure of the closeness of the results obtained when analysis on the same
sample is repeated; agreement between replicate measurements.