Chemistry and Measurements Study Guide
VAAL UNIVERSITY OF TECHNOLOGY: Chemistry and Measurements Study Guide 2026
Outcome 1: Chemistry and Measurements
What is Chemistry?
Definition: Chemistry is the branch of science that deals with the study of elements, including atoms, molecules, compounds, ions, etc.
It examines their chemical composition, characteristics, structure, and reactions.
Additionally, chemistry studies the chemical interactions and bonding between elements, atoms, and molecules.
Branches of Chemistry
Environmental Chemistry: Studies the chemical and biochemical phenomena that occur in the environment.
Analytical Chemistry: Focuses on the qualitative and quantitative analysis of substances.
Organic Chemistry: Studies the structure, properties, and reactions of carbon-containing compounds.
Inorganic Chemistry: Concerns the properties and behavior of inorganic compounds.
Physical Chemistry: Combines principles of physics and chemistry to study how matter behaves on a molecular and atomic level.
Quantum Chemistry: Studies the behavior of atoms and molecules using the principles of quantum mechanics.
Polymer Chemistry: Focuses on the chemical compounds formed by polymerization.
Biophysical Chemistry: Examines the physical principles of biological processes.
Nuclear Chemistry: Deals with radioactivity, nuclear processes, and properties of radioactive materials.
Safety and Practical Considerations
Understanding safety protocols is critical for laboratory work in chemistry.
Measurements in Chemistry
Units of Measurement
Definition: A unit of measurement is a definite magnitude of a quantity that is defined by conversion or law.
Metric System: The International System of Units (SI) is the common measuring system used in science and health, except in the US.
Importance: A number without a unit is meaningless.
Standard Units of Measurement
Measurement | Metric Unit | SI Unit |
|---|---|---|
Length | meter (m) | meter (m) |
Volume | liter (L) | cubic meter (m³) |
Mass | gram (g) | kilogram (kg) |
Temperature | degree Celsius (°C) | kelvin (K) |
Time | second (s) | second (s) |
Scientific Notation
Definition: A method of expressing very large or very small numbers as the product of a decimal less than 10, multiplied by a power of 10.
A number in scientific notation consists of three parts: a coefficient, a power of 10, and a unit of measurement.
Example 1: Expressing large numbers in a compact form.
Example 2: Handling very small measurements using scientific notation.
Measured Numbers and Significant Figures
Measured Numbers: Values obtained through measurement with a measuring tool (e.g., height, weight, temperature).
Significant Figures (SF): In a measured number, SFs include all digits, with the last digit being estimated.
Key Rules of SFs:
All non-zero numbers are always counted as significant figures.
Zeros may or may not be significant, depending on their position:
Significant: One or more zeros between nonzero digits, trailing zeros at the end of a decimal number, zeros in scientific notation.
Not Significant: Leading zeros in a decimal number, placeholder zeros in large numbers without decimals.
Examples of Significant Figures Counting:
122.35 m has 5 sig figs.
0.0050830 has 5 sig figs.
190000 can have 2-6 sig figs depending on context.
Calculating Significant Figures in Calculations
Rounding Rules:
If the first digit to be dropped is 4 or less, drop it and all following digits.
If the first digit to be dropped is 5 or greater, increase the last retained digit by 1.
Prefixes and Conversion Factors
Definition of a Prefix: A symbol added to metric base units to increase or decrease the value by a factor of 10.
Examples of Prefixes:
1 Kilometer (1 km) = 1000 meters
1 Kilogram (1 kg) = 1000 grams
Metric Prefix Table:
Prefix
Symbol
Numerical Value
Scientific Notation
tera
T
1,000,000,000,000
$10^{12}$
giga
G
1,000,000,000
$10^{9}$
mega
M
1,000,000
$10^{6}$
kilo
k
1,000
$10^{3}$
deci
d
0.1
$10^{-1}$
centi
c
0.01
$10^{-2}$
milli
m
0.001
$10^{-3}$
micro
μ
0.000001
$10^{-6}$
nano
n
0.000000001
$10^{-9}$
pico
p
0.000000000001
$10^{-12}$
Writing Conversion Factors
A conversion factor is an arithmetic multiplier that converts a quantity from one set of units to another, based on equalities.
Example Equality: 2 hours = 120 minutes, which can be expressed as:
$1 ext{ hour} = 60 ext{ minutes}$
Sample Problems in Unit Conversion
Convert 18.2 mm to meters by identifying the units and using the conversion factor.
Convert weight from pounds to kilograms for dosage calculation in medical settings.
Density
Definition: Density is the relationship between the mass and volume of a substance.
Formula: Density ($d$) is calculated as:
Specific Gravity
Definition: Specific gravity is the relationship between the density of a substance and the density of water.
Outcome 2: Matter and Energy
Definitions and Concepts
Matter: Anything that occupies space and has mass, composed of atoms.
Atoms: The smallest identifiable unit of an element that cannot be broken down chemically.
Molecules: Groups of two or more atoms that form the smallest unit of a pure substance retaining its composition and properties.
States of Matter
Solid: Atoms/molecules are closely packed in fixed locations.
Liquid: Atoms/molecules are close but can move past each other.
Gas: Atoms are far apart and move freely.
Types of Matter
Pure Substances: Composed of one type of atom or molecule.
Mixtures: Composed of two or more different types of atoms or molecules.
Properties of Matter
Physical Property: A characteristic that can be observed without changing the substance's composition (e.g., freezing point).
Chemical Property: A characteristic that can only be observed by changing the composition (e.g., decomposition).
Changes in Matter
Chemical Change: Involves the formation of new substances (e.g., combustion).
Physical Change: Changes in form but not in chemical identity (e.g., melting).
Energy Concepts
Energy: The ability to do work; comes in various forms (kinetic, potential, thermal, etc.).
Conservation of Energy: Energy cannot be created or destroyed, only transformed.
Temperature Scales
Celsius (°C): Freezing point at 0°C, boiling point at 100°C.
Fahrenheit (°F): Freezing point at 32°F, boiling point at 212°F.
Kelvin (K): Absolute temperature scale, 0 K is absolute zero.
Specific Heat
Definition: The amount of heat required to raise the temperature of 1 g of substance by 1°C.
Formula: The energy can be calculated based on specific heat and temperature change.
Sample Problem for Specific Heat
If 45.2 g of aluminum's temperature rises from 12.5 °C to 76.8 °C, calculate the total heat using its specific heat from the reference tables.