Chapter 1: Matter, Measurement, and Problem Solving

1.1 Atoms, Molecules, and Ions

Chemistry studies the nature of the matter around us.
The nature of matter is associated with the properties of the atoms, molecules, or ions that constitute it.
Chemistry seeks to understand the nature of matter by studying the behavior of atoms, molecules, and ions.
Two views are contrasted on the slide: Others’ view vs Chemists’ view.
- Others’ view
- Chemists’ view
Atoms
- Smallest chemically-indivisible fundamental particles of matter.
- Neutral (chargeless).
- Examples: Helium (He), Neon (Ne), Gold (Au), Mercury (Hg).
Molecules
- Smallest chemical species that can exist discretely in nature.
- May consist of one or more atoms.
- Examples: Neon (Ne), Oxygen (O$2$), Hydrogen (H$2$), Chlorine (Cl$2$), Sulfur (S$8$), Water (H$_2$O).
Ions
- Charged species formed by gaining or losing electrons.
- May consist of one or more atoms.
- Examples: Sodium ion ($\mathrm{Na^+}$), Chloride ion ($\mathrm{Cl^-}$), Sulfate ion ($\mathrm{SO_4^{2-}}$).
Note: Atoms of most elements are reactive and are not found freely in nature; they are found in different substances as molecules or ions.

1.2 The Scientific Approach

The Scientific Approach is a systematic process of inquiry conducted to understand a phenomenon, solve real-world problems, or address knowledge gaps.
It involves key steps such as:
- Identifying the problem
- Conducting observations
- Formulating a hypothesis
- Developing and conducting experiments
- Data collection, analysis, and interpretation
Key characteristics include:
- Observation
- Formulation of hypotheses
- Experimentation
- Generation of laws and theories
Observation and Experimentation
- Observations are often coupled with experimentation but can be conducted before or during experiments.
- Experiments are highly controlled procedures designed to generate observations or data that confirm or refute a hypothesis.
- Some observations and experiments are qualitative (how a process happens); others are quantitative (measuring or quantifying something about the process).
- Observations may or may not consist of measurements.
- Observations often lead scientists to formulate a hypothesis.
- Example: Antoine Lavoisier (1743–1794) studied combustion by burning objects in closed containers (scientific method), observed how things burn (qualitative), measured mass of objects before and after burning (quantitative), and noticed that there was no change in the total mass of material within the container during combustion.
Hypothesis
- A hypothesis is a tentative interpretation or explanation of observations.
- It also makes predictions to be tested through experiments.
- A good hypothesis is falsifiable – can be proven or disproven. If disproven, the scientist must modify and retest or discard the hypothesis.
- Example: Lavoisier explained his observations (the mass of ash is greater than the mass of the substance that burned) on combustion by hypothesizing that when a substance burns, it combines with a component of air.
Scientific Law
- Lavoisier’s experiments led to the law of conservation of mass: matter is neither created nor destroyed in a chemical reaction.
- A law is a brief statement that summarizes past observations and predicts future ones. It describes what happens during certain phenomena. Such laws are subject to experiments, which can prove or disprove them.
Scientific Theory
- John Dalton’s atomic theory explains how atoms combine in fixed ratios to form compounds, providing explanations for the behavior and composition of matter.
- A scientific theory explains both what happens (observations) and why it happens (underlying reasons or mechanisms).
- “What” refers to observations and descriptions of a phenomenon; “Why” refers to underlying reasons or mechanisms.
- Like laws, theories are subject to experiments and can be proven or disproven.
The Scientific Approach to Knowledge (overview of flow)
- Observations
- Experiments
- The Scientific Method
- Hypothesis (can be confirmed or revised)
- Theory (can be revised) / Law (can be revised)
- Experimentation continues to test, confirm, or revise
Self-test (1)
- Antoine Lavoisier predicted from his observation that when a substance burns it combines with a component of air. To prove it, he studied the combustion of substances in closed containers, and generalized that matter is neither created nor destroyed in a chemical reaction. Which component of the scientific approach does the underlined statement correspond to?
- A. Hypothesis B. Experimentation C. Theory D. Law
Self-test (2)
- Antoine Lavoisier predicted from his observation that when a substance burns it combines with a component of air. To prove it, he studied the combustion of substances in closed containers, and generalized that matter is neither created nor destroyed in a chemical reaction. Which component of the scientific approach does the underlined statement correspond to?
- A. Hypothesis B. Experimentation C. Theory D. Law
Self-test (3)
- Antoine Lavoisier predicted from his observation that when a substance burns it combines with a component of air. To prove it, he studied the combustion of substances in closed containers, and generalized that matter is neither created nor destroyed in a chemical reaction. Which component of the scientific approach does the underlined statement correspond to?
- A. Hypothesis B. Experimentation C. Theory D. Law

1.3 The Classification of Matter

Matter is anything that occupies space and has mass.
- Examples: textbook, desk, chair, body.
Matter can be classified by its state (physical form) and by its composition (basic components).

1.4 Physical Classification of Matter

Physical states: solid, liquid, and gas
- Solid
- Particles closely packed; fixed volume; rigid shape.
- Two types of solid: Crystalline and Amorphous
  - Crystalline solids: regularly arranged particles (e.g., table salt, diamond)
  - Amorphous solids: irregularly arranged particles (e.g., glass, plastic)
- Liquid
- Particles packed about as closely as in solid; fixed volume; no fixed shape.
- Gas
- Particles have a lot of space; free to move; compressible; no fixed volume or shape.
Matter by components
- Pure substance vs Mixture
- Pure substance: made of only one component; fixed composition.
- Mixture: two or more chemically distinct components with varying proportions.
- Pure substances split into Elements and Compounds
- Elements: atoms of similar identity; cannot be chemically broken down into simpler substances.
- Compounds: atoms of different elements; can be chemically decomposed into simpler substances.
- Mixtures split into Heterogeneous and Homogeneous
- Heterogeneous: components identifiable with naked eye or microscope (e.g., blood, milk, salt and sand).
- Homogeneous: components not identifiable with naked eye or microscope; uniform composition (e.g., sugar-water solution, air, brass).
The Classification by Components (Examples)
- Sulfur powder, Helium gas (balloon), Iron, Copper, Water, Distilled water, Sodium chloride, Carbon dioxide, Muddy water, Water and oil, Milk, Blood, Iodized salt, Tap water, Drinking water, Natural spring water, Air, Beverage and alcoholic drinks.

Separation of Mixtures

Mixtures are physically separable into their components using techniques such as decantation, filtration, and distillation.
- Sand and water can be separated by decantation (allow sand to settle; pour off water) or by filtration (more effective).
- Water–ethanol mixture (BP = 78 °C) can be separated by distillation (boil off ethanol, which is more easily vaporizable than water).
- Boiling points: ext{BP}_{\mathrm{water}} = 100^{\circ}\mathrm{C} (212 °F)
- \text{BP}_{\mathrm{ethanol}} = 78^{\circ}\mathrm{C} (173 °F)
- Aquarium water can be purified by filtration using sponge filters or canister filters.
Notational and rounding notes (from Page 1 content)
- Example numeric entries (likely related to rounding or significant figures):
- 2.345, \; 0.07, \; 5.9, \; 2.9975, \; -0.221
- 5.4125 \rightarrow 5.41
- 5.679 \rightarrow 5.7
- These illustrate rounding or significant-figure handling in measurement data.