Chemistry: The Central Science - Flashcards for Chapter 1

Chemistry: The Central Science

1. Introduction: Matter, Energy, and Measurement

• Chemistry is defined as the study of matter, its properties, and the changes it undergoes.

• Chemistry is crucial for understanding various science-related fields.

1.1 Classifications of Matter

• Matter is anything that has mass and occupies space.

States of Matter

• The three main states of matter are:

  • Solid

  • Liquid

  • Gas

• Examples of states:

  • Ice (solid)

  • Liquid water (liquid)

  • Water vapor (gas)

Composition of Matter

• Matter can be classified based on its composition:

  • Substances: have distinct properties and a consistent composition across samples.

  • Elements: Cannot be decomposed into simpler substances (e.g., Carbon, Helium).

  • Compounds: Can be decomposed into simpler substances as they consist of more than one element (e.g., water H₂O).

• Atoms: The fundamental building blocks of matter, specific to each element.

  • An element is made of one unique atom type, whereas a compound consists of different elements.

• Molecules: Groups of connected atoms.

Representing Elements

• Chemists represent elements using symbols (one or two letters, first letter capitalized).

• Some elements use Latin or Greek roots for their symbols.

• Example Elements and Symbols:

  • Carbon (C)

  • Hydrogen (H)

  • Oxygen (O)

  • Iron (Fe) (from ferrum)

  • Sodium (Na) (from natrium)

Elements and Composition

• There are 118 known elements.

• Only five elements constitute 90% of the Earth’s crust by mass; three elements constitute 90% of the human body by mass, highlighting the significance of oxygen.

Compounds and Composition

• Compounds maintain a definite composition, meaning the ratio of each atom type remains constant (Law of Constant Composition or Definite Proportions).

Mixtures

• Mixtures show properties of their constituent substances and can be classified as:

  • Homogeneous Mixtures: Same composition throughout (also known as solutions).

  • Heterogeneous Mixtures: Composition varies throughout.

• You can classify matter using a decision scheme involving mixtures, elements, and compounds.

1.3 Properties of Matter

• Properties are categorized into two main types:

  • Physical Properties: Observable without changing the substance. Examples include:

  • Color

  • Odor

  • Density

  • Melting point

  • Boiling point

  • Hardness

  • Chemical Properties: Observable only when a substance undergoes a change. Example:

  • Flammability

Further Distinction of Properties

• Intensive Properties: Independent of the amount present; useful for identification. Examples:

  • Density

  • Boiling point

  • Color

• Extensive Properties: Dependent on the amount present. Examples:

  • Mass

  • Volume

  • Energy

Changes in Matter

• Physical Changes involve changes in state, temperature, and volume without altering the substance’s composition. Examples:

  • Melting ice

  • Water evaporating

• Chemical Changes result in new substances forming, such as:

  • Combustion

  • Oxidation

  • Decomposition

Separating Mixtures

• Mixtures can be separated based on physical properties using methods like:

  • Filtration: Separates solids from liquids.

  • Distillation: Uses boiling point differences to separate liquid components of a homogeneous mixture.

  • Chromatography: Separates substances based on their adherence to solid surfaces.

1.4 Energy

• Energy is defined as the capacity to do work or transfer heat.

• Work: Energy transfer caused by applying force to displace an object.

• Heat: Energy that causes a change in temperature.

• Force: A push or pull exerted on an object.

Two Fundamental Forms of Energy

• Kinetic Energy (KE): Energy of motion, determined by mass and velocity.

  • KE formula: KE = rac{1}{2}mv^2 where m is mass and v is velocity.

• Potential Energy (PE): Stored energy based on an object’s position relative to others.

1.5 Units of Measurement

• Measurement is essential in chemistry for quantitative analysis.

Units of Measurement - SI Units

• Système International d’Unités (SI) includes different base units for quantities:

  • Length: Meter (m)

  • Mass: Kilogram (kg)

  • Temperature: Kelvin (K)

  • Time: Second (s)

  • Amount of substance: Mole (mol)

  • Electric current: Ampere (A)

  • Luminous intensity: Candela (cd)

Units of Measurement - Metric System

• Common base units include:

  • Mass: gram (g)

  • Length: meter (m)

  • Time: seconds (s)

  • Temperature: Kelvin (K)

  • Volume: liter (L) or cubic centimeter (cm³).

Metric System Prefixes

• The metric system utilizes prefixes to express magnitudes:

  • Peta (P): $10^{15}$

  • Tera (T): $10^{12}$

  • Giga (G): $10^{9}$

  • Mega (M): $10^{6}$

  • Kilo (k): $10^{3}$

  • Deci (d): $10^{-1}$

  • Centi (c): $10^{-2}$

  • Milli (m): $10^{-3}$

  • Micro (µ): $10^{-6}$

  • Nano (n): $10^{-9}$

  • Pico (p): $10^{-12}$

  • Femto (f): $10^{-15}$

  • Atto (a): $10^{-18}$

  • Zepto (z): $10^{-21}$

Mass and Length Units

• Mass is measured in kilograms in SI, with grams being the metric unit (1 kg = 2.20 lb).

• Length is measured in meters in SI (1 m = 1.09 yd).

Temperature Measurement

• Temperature indicates the degree of heat; higher temperatures lead to heat flow away from the object.

• Celsius and Kelvin are common scales:

  • Celsius scale:

  • Freezing Point: 0°C

  • Boiling Point: 100°C

  • Kelvin scale:

  • No negative temperatures; Absolute Zero: 0 K

  • Formula: K = °C + 273.15

Volume Measurement

• Volume is derived from length measurements. Common units are:

  • Liter (L)

  • Milliliter (mL) (1 mL = 1 cm³)

Density Measurement

• Density is derived as ext{Density} = rac{ ext{Mass}}{ ext{Volume}}

• Common densities at 1g/cm³ are:

  • Air: 0.001 g/cm³

  • Water: 1.00 g/cm³

  • Iron: 7.9 g/cm³

  • Gold: 19.32 g/cm³

Energy Units

• The Joule (J) is the unit of energy. If a 2 kg object moves at 1 m/s, it has 1 J of kinetic energy:

  • KiloJoule (kJ) commonly used in chemical contexts.

  • Historical conversion: 1 calorie = 4.184 Joules (Note: Nutritional calorie = 1000 calories)

1.6 Uncertainty in Measurements

• Measuring devices have various accuracies; all measurements carry some level of uncertainty.

• The last digit of a recorded measurement is understood to be reliable but not exact.

Types of Numerical Data in Science

• Exact Numbers: Known with certainty (e.g., 12 eggs in a dozen).

• Inexact (Measured) Numbers: Subject to limitations; may exhibit errors from instruments or human reading variance.

• Uncertainties are inherent in these measurements.

Precision versus Accuracy

• Precision: How closely measurements agree with one another.

• Accuracy: How closely measurements reflect the true or expected value.

• Evaluating multiple measurements helps establish standard deviations.

Significant Figures

• All digits, including uncertain ones, denote significant figures. Proper handling ensures accurate representation of data:

  • Non-zero digits are always significant.

  • Zeroes between non-zero digits are significant.

  • Leading zeroes are not significant; trailing zeroes are significant only with a decimal point.

Significant Figure Rules in Calculations

• The least certain measurement dictates the number of significant figures in a result, adjusting for:

  • Addition/Subtraction: Round to the least significant decimal place.

  • Multiplication/Division: Round to the same number of significant figures as the measurement with the fewest significant figures.

• Example:

  • Values: 20.42 (2 decimal places), 1.322 (3 decimal places), 83.1 (1 decimal place).

Dimensional Analysis

• A method for converting between units using conversion factors (e.g., 1 in = 2.54 cm).

• It requires creating ratios to adjust units appropriately throughout calculations.

1.7 Conclusion

• Understanding the classifications of matter, properties, energy, measurement, and significant figures is foundational in the study of chemistry. The precision and accuracy in measurements play critical roles in scientific research and application.