Basic Chemistry and the Scientific Method

Basic Chemistry Concepts

• Chemistry is the study of substances in terms of their composition, structure, properties, and reactions.
• Chemicals are substances with consistent composition and properties.
• Examples include sugar, water, and salt.
• Light, heat, energy, sound, magnetism, and reflection are not considered chemicals.

The Scientific Approach to Knowledge

• Scientific knowledge is empirical, based on observation and experimentation.
• The scientific method is a process for understanding nature through observation and experimentation.
• Key characteristics of the scientific method include observations, hypothesis formulation, experimentation, and conclusion/theory formulation.

Scientific Method Steps

• Observation (noting and recording natural phenomena; AKA data)
• Hypothesis (a tentative explanation of facts, based on reasoning and evidence; often in an if-then statement; must be falsifiable)
• Experiment (a procedure to test the hypothesis)
• Theory/Conclusion (a well-established hypothesis or set of hypotheses that explains natural phenomena)
• Law (a brief statement summarizing past observations and predicting future ones)

Everyday Scientific Thinking

• Observations of everyday phenomena can be used to form hypotheses and test them through experiments.
• A hypothesis can be tested and validated or invalidated through experiments, leading to conclusions.

Scientific Measurement

• Qualifiable data are observational and subjective.
• Quantifiable data depend on numbers and units (empirical).
• Scientific instruments are utilized to gather empirical data with standardized units, these units being crucial.

Units of Measurement

• Units quantify measurements, important for 99.9% of numbers.
• SI (International System of Units) is a standardized metric system of measurement.
• Common SI units include meters (m) for length, liters (L) and milliliters (mL) for volume, kilograms (kg) for mass, seconds (s) for time, Celsius (°C) and Kelvin (K) for temperature etc.

Standard and Scientific Notation

• Scientific notation represents very large or very small numbers using a coefficient and a power of ten.
• The coefficient must be at least 1 but less than 10, the number of spaces moved to obtain the coefficient is shown as a power of ten.

Significant Figures

• Scientific measurements use significant figures (SF), including estimated digits, to convey accuracy.
• All non-zero digits are significant.
• Zeros may be significant depending on their position in the number or written in scientific notation.

Exact Numbers

• Exact numbers are obtained from counting discrete items or from defined relationships between units (e.g., 1 ft = 12 inches).
• Exact numbers do not limit the number of significant figures in calculations.

Conversion Factors

• Conversion factors relate different units that measure the same quantity.
• Conversion factors are often derived from equalities and used to change units in calculations.
• Conversion factors based on defined equalities do not affect the number of significant figures in an answer.
• Conversion factors based on measured quantities affect the number of significant figures.

Physical Properties

• Physical properties describe a substance without changing its chemical identity.
• Examples include color, shape, melting point, boiling point, and physical state.

Physical Changes

• Physical changes alter a substance's physical state or appearance, but not its chemical composition.
• Examples include boiling, freezing, dissolving, and cutting.

Chemical Properties

• Chemical properties indicate a substance's ability to interact with other substances and transform into a new substance.

Chemical Changes

• Chemical changes result in the formation of new substances with different chemical and physical properties.
• Examples include burning, rusting, and cooking.

Atomic Structure

• Atoms are the basic building blocks of matter, too small to be seen with the naked eye.
• Atoms are composed of subatomic particles: protons (positive charge), neutrons (no charge), and electrons (negative charge).
• Protons and neutrons are located in the nucleus of the atom and electrons orbit the nucleus.
• The mass of an atom is primarily determined by the masses of protons and neutrons.

Atomic Number

• The atomic number represents the number of protons in an atom and is characteristic of each element.
• The atomic number is used to identify the element and locate it on the periodic table.

Mass Numbers

• The mass number is the sum of protons and neutrons in an atom's nucleus.
• Mass number is used to determine the number of neutrons in a given isotope.

Isotopes

• Isotopes are atoms of the same element that have the same atomic number but different mass numbers (because different number of neutrons)

Atomic Mass

• The atomic mass of an element is a weighted average of the masses of its naturally occurring isotopes.
• Atomic mass values are listed below the element's symbol on the periodic table.

Density

• Density compares mass to volume.
• D = m/V (Density = mass/volume)
• Density is a physical property that can be used to identify substances.
• Different substances generally have different densities.
• The density of a solid or liquid is often expressed in g/cm3 or g/mL, while the density of a gas is often expressed in g/L.

More notes on Density

• The density of a substance depends on the closeness of packing of its particles.
• Higher densities usually result from particles packed closely together.
• Substances with lower density will have its particles further apart.

This quiz covers fundamental concepts in chemistry, including the definition of chemicals and the characteristics of scientific knowledge. It also explores the steps of the scientific method, highlighting observations, hypothesis formulation, and experimentation. Test your understanding of these essential scientific principles!