Introduction to Chemistry

• Chemistry is the study of matter, properties, changes, and associated energy.

Matter

• Matter has both mass and volume, examples include books, planets, trees, professors, and students.

Composition

• Composition refers to the types and amounts of simpler substances in matter samples.

Properties

• Properties are the characteristics that give substances unique identities.

States of Matter

• Solids have a fixed shape and volume and can be hard/soft or rigid/flexible.
• Liquids have variable shapes conforming to their container, fixed volume, and an upper surface.
• Gases lack fixed shapes or volumes.

Physical Properties

• Physical properties are shown by a substance itself, without interaction, examples include color, melting point, boiling point, and density

Chemical Properties

• Are properties displayed when a substance interacts or transforms, examples include flammability and corrosiveness.

Change of State

• A change of state is a physical change where the physical form changes, but the composition remains unchanged
• Changes in physical state are reversible by changing the temperature.
• Chemical changes are not reversed by changing temperature

Energy

• Energy is the ability to do work.

Potential energy

• Potential energy is energy due to an object's position.

Kinetic Energy

• Kinetic Energy is energy due to an object's movement.
• Total Energy = Potential Energy + Kinetic Energy
• Lower energy states are more stable and favored.
• Energy is conserved and can be converted between forms.

Gravitational System

• Potential energy gained from lifting a weight converts to kinetic energy as it falls.

Two-Ball Spring System

• Potential energy gained by stretching a spring converts to kinetic energy when released.

SI Base Units

• Mass: kilogram (kg).
• Length: meter (m).
• Time: second (s).
• Temperature: kelvin (K).
• Amount of substance: mole (mol).
• Electric current: ampere (A).
• Luminous intensity: candela (cd).

Common Decimal Prefixes Used With SI Units

• tera (T): 1,000,000,000,000 or 1x10¹²
• giga (G): 1,000,000,000 or 1x10⁹
• mega (M): 1,000,000 or 1x10⁶
• kilo (k): 1000 or 1x10³
• hecto (h): 100 or 1x10²
• deka (da): 10 or 1x10¹
• deci (d): 0.1 or 1x10⁻¹
• centi (c): 0.01 or 1x10⁻²
• milli (m): 0.001 or 1x10⁻³
• micro (µ): 0.000001 or 1x10⁻⁶
• nano (n): 0.000000001 or 1x10⁻⁹
• pico (p): 0.000000000001 or 1x10⁻¹²
• femto (f): 0.000000000000001 or 1x10⁻¹⁵

Problem Solving

• Measured quantities consist of a number and a unit
• Units are manipulated like numbers.

Conversion Factor

• A conversion factor is a ratio of equivalent quantities expressing a quantity in different units
• A conversion factor is chosen and set up so that all units cancel except those required for the answer.

Systematic Approach Includes following steps

• State the problem, clarify knowns, suggest steps, prepare a visual summary.
• Provide the solution, check, comment, and follow-up.

Density

• Density is mass divided by volume.
• At a given temperature and pressure, density is a characteristic physical property with a specific value.

Temperature

• Temperature measures how hot or cold an object is relative to another
• Heat is the energy flowing from higher to lower temperature objects.

Temperature Scales

• Celsius (°C): Based on the freezing and boiling points of water.
• Kelvin (K): The "absolute temperature scale" starts at absolute zero and uses the same degree size as Celsius, but without degree signs (°).
• Fahrenheit (°F): Primarily used in the U.S., differs in degree size and zero points from Celsius and Kelvin.

Temperature Conversion Formulas

• T(in K) = T (in °C) + 273.15
• T(in °C) = T(in K) – 273.15
• T(in °F) = (9/5)T(in °C) + 32
• T(in °C) = T(in °F) − 32

Significant Figures

• Each measurement has uncertainty; the rightmost digit is always estimated.
• Recorded digits, both certain and uncertain, are significant figures.
• More significant figures indicate greater certainty.

Rules for Determining Significant Digits

• All non-zero digits are significant.
• Zeros used to position the decimal point aren't significant.
• Zeros ending a number are significant whether before or after the decimal point, as long as a decimal point is present.
• If no decimal point is present, zeros at the end are not significant.

Rules for Calcuations

• Multiplication and division: The answer has the same number of significant figures as the measurement with the fewest significant figures.
• Addition and subtraction: The answer has the same number of decimal places as the measurement with the fewest decimal places.

Rules for Rounding

• If the digit removed is more than 5, the preceding number increases by 1.
• If the digit removed is less than 5, the preceding number is unchanged.
• If the digit removed is 5 followed by zeros/no digits, the preceding number increases by 1 if odd, and remains unchanged if even.

Exact Numbers

• Exact numbers have no uncertainty, and are either by definition or count.
• Exact numbers do not limit the number of significant digits in calculations.

Precision, Accuracy, and Error

• Precision: How close measurements are to each other.
• Accuracy: How close each measurement is to the actual value.
• Systematic error: Produces values consistently higher/lower, part of the experimental system.
• Random error: Produces values that are both higher and lower, and always occurs.