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Chemistry: Vocabulary Flashcards – The Molecular Nature of Matter and Change

States of Matter

  • A solid has a fixed shape and volume. Solids may be hard or soft, rigid or flexible.
  • A liquid has a varying shape that conforms to the shape of the container, but a fixed volume. A liquid has an upper surface.
  • A gas has no fixed shape or volume and therefore does not have a surface.

The Physical States of Matter (Figure 1.1)

  • Solid: Particles are close together and organized.
  • Liquid: Particles are close together but disorganized.
  • Gas: Particles are far apart and disorganized.

Physical and Chemical Properties

  • Physical Properties: properties a substance shows by itself without interacting with another substance. Examples: color, melting point, boiling point, density.
  • Chemical Properties: properties a substance shows as it interacts with, or transforms into, other substances. Examples: flammability, corrosiveness.

The Distinction Between Physical and Chemical Change

  • Physical change: change in form or state where composition remains the same.
  • Chemical change: change that results in a new substance with a different composition.
  • Visuals (Figure 1.2) illustrate how changes can be categorized by whether composition changes.

Sample Problem 1.1 – Problem and Plan: Visualizing Change on the Atomic Scale

  • PROBLEM: The scenes depict an atomic-scale view of a substance A undergoing two changes. Decide whether each scene shows a physical or a chemical change.
  • PLAN: Determine if composition changes. If composition changes, the change is chemical; if composition remains the same, the change is physical.
  • KEY: Composition is indicated by the numbers/colors of particles; unchanged composition => physical change; changed composition => chemical change.

Temperature and Change of State

  • A change of state is a physical change: physical form changes, composition does not.
  • Changes in physical state are reversible.
  • By changing the temperature you can cause changes of state; a chemical change cannot simply be reversed by a change in temperature.

Some Characteristic Properties of Copper (Table 1.1)

  • A set of properties used to characterize copper (examples include melting point, density, appearance, reactivity). Specific values appear in Table 1.1 and accompanying figures.

Sample Problem 1.2 – Problem and Plan: Distinguishing Between Physical and Chemical Change

  • PROBLEM: Decide whether each process is primarily physical or chemical and explain briefly:
    • (a) Frost forms as the temperature drops on a humid winter night.
    • (b) A cornstalk grows from a seed that is watered and fertilized.
    • (c) A match ignites to form ash and a mixture of gases.
    • (d) Perspiration evaporates when you relax after jogging.
    • (e) A silver fork tarnishes slowly in air.
  • PLAN: Determine whether the substance changes its composition or just its form.

Energy in Chemistry

  • Energy is the ability to do work.
  • Potential energy is energy due to the position of an object.
  • Kinetic energy is energy due to the movement of an object.
  • Total Energy is the sum of Potential and Kinetic energy:
    E{ ext{total}} = E{ ext{potential}} + E_{ ext{kinetic}}

Energy Changes

  • Lower energy states are more stable and favored over higher energy states.
  • Energy is neither created nor destroyed; it is conserved.
  • Energy can be converted from one form to another.

Potential Energy Is Converted to Kinetic Energy (Examples 1–4)

  • 1) Gravitational system: potential energy gained when a weight is lifted is converted to kinetic energy as the weight falls; a lower energy state is more stable.
  • 2) A system of two balls attached by a spring: potential energy of a stretched spring converts to kinetic energy when released.
  • 3) A system of oppositely charged particles: potential energy when charges are separated converts to kinetic energy as attraction pulls them together.
  • 4) A system with fuel and exhaust: chemical potential energy of fuel converts to kinetic energy of the moving car.
  • In all cases, energy is conserved through transformation.

The Scientific Approach: Developing a Model (Figure 1.4)

  • Observations → Hypothesis → Experiment → Model → Further Experiment → (check compatibility and predictions) → Follow-up Problem
  • Hypothesis: tentative proposal that explains observations.
  • Model (Theory): set of conceptual assumptions that explains data from accumulated experiments and predicts related phenomena.
  • Model is revised/altered if experimental results or predictions do not support it.

SI Base Units (Table 1.2)

  • 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 (Table 1.3)

  • tera (T) = $10^{12}$
  • giga (G) = $10^{9}$
  • mega (M) = $10^{6}$
  • kilo (k) = $10^{3}$
  • hecto (h) = $10^{2}$
  • deka (da) = $10^{1}$
  • deci (d) = $10^{-1}$
  • centi (c) = $10^{-2}$
  • milli (m) = $10^{-3}$
  • micro (µ) = $10^{-6}$
  • nano (n