PreAP Chemistry Midterm Study Guide

Pre-AP Chemistry Midterm Study Guide 2025

1. Lab Safety and Equipment

• Review Flinn Safety Contract and Lab Equipment Drawings and Uses (notebook)

2. Unit 1.1: Particle View of States of Matter

• Enduring Understandings

  • Solids, liquids, and gases possess different properties due to particle motion and interactions.

  • All measurements contain uncertainty, impacting experimental design and data recording.

  • Energy transfer during heating, cooling, or state changes is influenced by particle interactions.

  • Observable gas properties can be experimentally measured and explained through particle motion.

a. Developing a Model of Matter

• Shared Model of Matter

  1. Particles are in constant motion.

  2. Average speed of particles increases with temperature.

  3. Macroscopic properties depend on particle-level motion.

  4. Particle interactions determine physical properties.

• Building Blocks of Matter

  • Different properties of matter related to particle states.

Types of Matter

Matter: Anything that has mass and volume

Element: a pure substance made out of only one type of atom

Compound: a substance that is made from the atoms of two or more elements that are chemically bonded

Atom: The smallest unit of an element or compound that retains all the properties of that element or compound

• some elements cannot exist on their own; they are known as diatomic elements making their smallest unit a molecule instead on an atom

Properties

Physical property: relates to a substance's physical nature

Chemical property: relates to a substances chemical nature

Extensive property: depends on the amount of matter present

Intensive property: does NOT depend on the amount of matter present

Ex: Water (H2O) has several physical properties, such as being a liquid at room temperature and having a boiling point of 100 degrees Celsius. Chemically, it can react with sodium to produce sodium hydroxide and hydrogen gas, demonstrating its chemical property. The mass of water is an extensive property, as it depends on the volume of water present, while its density is an intensive property because it remains the same regardless of the amount of water, at around 1 g/cm³.

3. States of Matter

• Classification

  • Solid: Definite shape and volume, very strong intermolecular forces.

  • Liquid: Indefinite shape, definite volume, strong intermolecular forces.

  • Gas: Indefinite shape and volume, weak intermolecular forces.

• Kinetic-Molecular Theory: Developed late 18th century; emphasizes continuous motion of particles.

Changes of State

• Vaporization: physical change of a liquid to a gas by addition of heat

• Evaporation: process of particles escaping from the surface of a non-boiling liquid to enter the gas state

  • Boiling: differs from vaporization, boiling is the change of liquid to bubbles of vapor that appear throughout the liquid

• Freezing: physical change of a liquid to a solid by the removal of heat

• Melting: physical change of a solid to a liquid by the addition of heat

• Condensation: physical change of a gas to a liquid by the removal of heat

4. Confidence in Measurement

• Scientific Notation and Significant Figures Rules:

  • Non-zero digits are significant.

  • Middle zeros are significant.

  • Leading zeros are not significant; trailing zeros are significant if a decimal is present.

  • Addition/Subtraction: Least number of decimal places.

  • Multiplication/Division: Least number of significant figures.

  • Exact numbers are significant.

• Steps to identify sig figs

  1. Find the first non-zero digit.

  2. Starting at the first non-zero digit, count the number of digits that are non-zero numbers or zeros between non-zero digits.

  3. If there is a decimal present, count trailing zeros.

  4. Label the number of significant figures.

• Steps to round to a given number of significant digits:

  1. Locate the significant figure for the degree of accuracy required.

  2. Look at the next digit immediately to the right. When the digit is 5 or more, round up by adding 1 to the previous digit. When the digit is less than 5 round down by keeping the previous digit the same.

5. Calibration and Uncertainties in Measurement

• Precision vs. Accuracy:

  • Precision: Reproducibility in measurements.

  • Accuracy: Closeness to the true value.

• Reporting Measurements: Must identify calibration, error (uncertainty), and estimated digit.

• Dimensional Analysis: Evaluates measurable quantities.

6. Relating Mass and Volume

• Methods to measure mass and volume, such as water displacement for irregular solids.

Unit 1.2: Phase Changes and Particle Interaction

• Phase changes and corresponding energy transfer due to particle interactions.

7. Vocabulary and Concepts

• Specific Heat (cp): Energy needed to raise temperature of 1g by 1°C (or K).

  • Formula: q = mcΔT where ΔT is Change in Temperature.

• Difference Between Heat and Temperature:

  • Heat: Amount of thermal energy.

  • Temperature: Average kinetic energy of molecules.

8. Transfer of Energy in Phase Change

• Calorimetry: Evaluates energy changes involved in phase transitions.

• Phase Diagrams: Illustrates conditions under which a substance exists as a solid, liquid, or gas under varying pressure and temperature.

  • Triple Point: Conditions at which solid, liquid, and gas coexist.

  • Critical Point: Conditions at which liquid and gas are indistinguishable.

9. Heating and Cooling Curves

• Visualizations of how substances respond to energy changes, indicating phase transitions through heating and cooling.

• Calorimetry enables calculation of energy changes during these processes.

Unit 1.3: Kinetic Molecular Theory

a. Identifying Common Gases

• Hydrogen: Popping sound when lit with a match.

• Oxygen: Glowing splint relights.

• Carbon Dioxide: Glowing splint extinguishes, reacts with limewater.

b. Properties of Gases

• Pressure: Dependent on force exerted and area size. Measured in Pa, atm, or kPa.

• Volume: Measured in liters.

• Temperature: Expressed in Kelvin or Celsius.

• Amount of Gas: Expressed in moles.

10. Standard Atmospheric Pressure

• Defined as 1 atm = 101 kPa = 760 mmHg.

11. KINETIC MOLECULAR THEORY Principles

• Gas particles move randomly, without attractions.

• The average kinetic energy relates to temperature.

• Collisions are elastic, conserving energy.

Unit 2: Classification of Matter

• Classification: Matter can be classified into mixtures and pure substances

• Mixtures consist of two or more particles, retaining unique properties and separable through physical processes.

• Atoms, Molecules, and Particles:

  • Pure substances have uniform composition, it includes elements and compounds; compounds have distinct properties.

• Periodic Table Basics:

  • Arranged by atomic numbers.

  • Elements in a column share properties; atomic mass is based on protons and neutrons.

  • Groups and periods indicate properties and electron configuration.

  • Isotopes are variants of elements with the same number of protons but different numbers of neutrons, affecting atomic mass.

• Partial Pressure: In gas mixtures, total pressure equals sum of individual partial pressures.

• Intermolecular Forces: Influences boiling/melting points and physical properties of substances.