Basic Chemistry Concepts

Basic Chemistry Concepts

• Chemistry is the study of substances, their composition, structure, properties, and reactions.
• Substances have consistent composition and properties.
• Light, heat, energy, sound, magnetism, and reflection are not considered chemicals.
• Matter is anything that has mass and occupies space.
• Matter is made of atoms.
• Atoms are the basic building blocks of matter.
• When two or more atoms bond, they form molecules.
• The arrangement of atoms/molecules dictates the physical property of the matter.
• Matter can be classified as a solid, liquid, or gas.
• A solid has a fixed volume and shape; its particles are closely packed together and vibrate but don't move around.
• A liquid has a fixed volume but takes on the shape of its container; its particles are loosely packed and can move past each other.
• A gas has neither a fixed volume nor a fixed shape and expands to fill its container; its particles are very far apart and move freely.

Scientific Method

• The scientific method is an empirical approach to understanding nature through observation and experimentation.
• Key characteristics include:
  • Observations: noting and recording natural phenomenons (AKA data)
  • Formulation of hypotheses: tentative explanations based on reason and evidence. Must be falsifiable (possible to prove wrong).
  • Experimentation: procedures to test hypotheses and gather more data.
  • Formulation of conclusions and theories: well-established hypotheses forming the basis of scientific theories. Theories explain why a natural phenomenon occurs and are validated by experimental results.
• A scientific law is a brief statement that summarizes past observations and predicts future ones. It does not explain why an event occurs, but rather states that a certain relationship exists.

Scientific Measurement

• Scientific data can be
• Qualifiable: observational and subjective (e.g., blue car)
• Quantifiable: measurable and objective (e.g., 538 ml of water) using standardized units.
• Units: needed to specify measurements. Most will have a unit.
• The metric system and SI system are commonly used.
  • SI (International System of Units) is based on the metric system and uses units like meters (m), kilograms (kg), seconds (s), Kelvin (K), etc,.
  • The metric system uses units like centimeters (cm), liters (L), and grams (g).
• Measured numbers: numbers obtained by using measuring tools,
• Length is measured in meters (m) or centimeters (cm).
• Volume is measured in liters (L) or milliliters (mL).
• Mass is measured in kilograms (kg) or grams (g).
• Temperature is measured in Celsius (°C) or Kelvin (K); conversion equations exist between Celsius and Fahrenheit (°F)
• Time is measured in seconds (s).

Significant Figures

• Significant figures in a measurement are all the certain digits plus the estimated one.
• Nonzero numbers are significant.
• Zeros between nonzero digits are significant.
• Zeros at the end of a decimal number are significant.
• Zeros used as placeholders in large numbers are not significant.
• Exact numbers (obtained by counting or definitions) have unlimited significant figures.

Scientific Notation

• Scientific notation is used for very large or very small numbers.
• It consists of a coefficient (1-10) and a power of 10.
• The power of 10 represents the number of places the decimal point has been moved.

Units of Measurement

• Units are critical to specify measurements.
• Various units represent different quantities.
• Equivalencies are used to convert between different units.

Density

• Density is the mass of a substance per unit volume (mass/volume).
• Density is a physical property used to describe a substance.
• Common units include: (g/cm³), (g/mL), or (g/L).
• Greater densities mean particles are tightly packed together.
• Substances can be identified based on their densities.

Physical Properties

• Physical properties are characteristics that can be observed or measured without changing the chemical identity of a substance.
• Examples include: shape, color, odor, melting point, boiling point, density and physical state.

Physical Changes

• Physical changes occur when a substance changes its physical state or appearance, but its chemical composition remains the same.
• Examples include: melting, boiling, freezing, dissolving, crushing, etc.

Chemical Properties

• Chemical properties describe a substance’s ability to react with other substances or undergo chemical changes to form new substances.

Chemical Changes

• Chemical changes occur when a substance transforms into a new substance (or substances) having different chemical and physical properties.
• Examples include: burning, rusting, cooking, digesting, etc

Atoms

• Atoms are the basic building blocks of matter.
• Atoms are too small to be seen with the naked eye.
• They consist of a nucleus and orbiting electrons.
• The nucleus contains protons and neutrons.

Atomic Number

• The atomic number is the number of protons in an atom and is specific to each element.
• It is listed on the periodic table above the elemental symbol.

Mass Number

• The mass number represents the total number of protons and neutrons within an atom's nucleus.
• It is not displayed on the periodic table.

Isotopes

• Isotopes are atoms of the same element that have different mass numbers.
• This means they have the same number of protons, but different numbers of neutrons.
• Isotopes are useful for identifying specific atoms of an element.