Chapter 3: Matter and Energy – Study Notes

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Chapter 3: Matter and Energy

3.1 Classification of Matter

Matter is anything that has mass and occupies space. It can be classified based on its composition into pure substances and mixtures.

Pure Substances: Have a fixed or definite composition. They are further classified as:
- Elements: Composed of only one type of atom (e.g., copper, aluminum, helium).
- Compounds: Consist of two or more elements chemically combined in a fixed ratio (e.g., water, hydrogen peroxide, table salt).
Mixtures: Contain two or more substances physically mixed, not chemically combined. The components can be present in varying proportions and separated by physical methods.

Aluminum can as an example of a pure substance Copper penny as an example of an element Hydrogen peroxide as an example of a compound Decomposition of sodium chloride into sodium and chlorine Separation of spaghetti and water as a physical method Filtration and chromatography as methods to separate mixtures

Types of Mixtures

Homogeneous Mixtures (Solutions): Uniform composition throughout; components are not visibly distinguishable (e.g., brass, air, salt water).
Heterogeneous Mixtures: Composition varies; different parts are visible (e.g., salad, sand in water).

Brass as a homogeneous mixture Scuba diver with nitrox tank as a homogeneous mixture Water and copper as a heterogeneous mixture Classification of matter diagram

3.2 States and Properties of Matter

Matter exists in three physical states: solid, liquid, and gas. Each state has distinct properties based on particle arrangement and movement.

Solids: Definite shape and volume; particles are closely packed in a fixed arrangement and vibrate in place.
Liquids: Definite volume but no definite shape; particles are close but can move past each other, allowing liquids to flow.
Gases: No definite shape or volume; particles are far apart and move rapidly, filling the container.

Amethyst as an example of a solid Water as a liquid Gas taking the shape and volume of its container

Characteristic	Solid	Liquid	Gas
Shape	Definite	Takes shape of container	Takes shape of container
Volume	Definite	Definite	Fills container
Arrangement of Particles	Fixed, very close	Random, close	Random, far apart
Interaction between Particles	Very strong	Strong	Essentially none
Movement of Particles	Very slow	Moderate	Very fast
Examples	Ice, salt, iron	Water, oil, vinegar	Water vapor, helium, air

Table comparing solids, liquids, and gases

Physical Properties

Observed or measured without changing the substance's identity (e.g., color, melting point, density).
Examples: Copper is reddish-orange, shiny, and a good conductor of heat and electricity.

Copper cookware as an example of physical properties

Physical and Chemical Changes

Physical Change: Alters physical form, not composition (e.g., melting, boiling, dissolving, cutting).
Chemical Change: Produces new substances with different properties (e.g., rusting, burning, caramelizing sugar).

Gold hammered into leaf as a physical change Gold ingot and gold leaf as an example of physical change Sugar caramelizing as a chemical change

Physical Changes	Chemical Changes
Water boils to form vapor	Silver reacts in air to form a black coating
Copper drawn into wires	Wood burns to form ashes, CO2, and water vapor
Sugar dissolves in water	Heating sugar forms caramel
Paper cut into confetti	Iron rusts to form Fe2O3

Table of physical and chemical changes

	Physical	Chemical
Property	Color, shape, odor, melting point, density	Ability to form new substances (e.g., burning, rusting)
Change	Change in state or shape, identity retained	Original substance converted to new substances

Summary of physical and chemical properties and changes

3.3 Temperature

Temperature measures how hot or cold an object is compared to another. It is measured in Celsius (°C), Fahrenheit (°F), or Kelvin (K).

Celsius (°C): Used in science; water freezes at 0°C and boils at 100°C.
Fahrenheit (°F): Common in the US; water freezes at 32°F and boils at 212°F.
Kelvin (K): Used in scientific measurements; absolute zero is 0 K (−273°C).

Digital ear thermometer Outdoor thermometer Temperature scales comparison Boiling and freezing points on three temperature scales

Temperature Conversions

To convert °C to °F:
To convert °F to °C:
To convert °C to K:

Temperature conversion equations Temperature conversion problem analysis

Example	Fahrenheit (°F)	Celsius (°C)	Kelvin (K)
Sun	9937	5503	5776
Water boils	212	100	373
Normal body temperature	98.6	37.0	310
Water freezes	32	0	273
Absolute zero	-459	-273	0

Table comparing temperatures Body temperature ranges and health

3.4 Energy

Energy is the ability to do work. It exists as kinetic energy (energy of motion) and potential energy (stored energy due to position or composition).

Kinetic Energy: Associated with moving objects (e.g., rollerblading, mowing the lawn).
Potential Energy: Stored energy (e.g., water behind a dam, gasoline in a tank).

Water behind a dam as potential energy, flowing water as kinetic energy

Heat and Units of Energy

Heat: Energy associated with the motion of particles; measured in joules (J) or calories (cal).
1 kilojoule (kJ) = 1000 J
1 kilocalorie (kcal) = 1000 cal
1 cal = 4.184 J

Example Calculation: To convert 150 J to calories: