Chapter 3: Matter and Energy – Structured Study Notes

Matter and Energy

Learning Goals

• Classification of Matter: Distinguish between pure substances and mixtures.

• States and Properties of Matter: Identify and describe the physical and chemical properties and states of matter.

• Temperature: Convert temperatures between Celsius and Kelvin scales.

• Energy: Define and differentiate between kinetic and potential energy; convert between energy units.

• Energy and Nutrition: Calculate food energy in kilocalories (kcal) or kilojoules (kJ).

• Specific Heat: Use specific heat to calculate heat loss or gain.

• Changes of State: Describe and calculate energy changes during phase transitions.

Classification of Matter

Pure Substances and Mixtures

Matter is anything that has mass and occupies space. It can be classified by composition:

• Pure Substances: Matter with a fixed or definite composition.

• Mixtures: Matter composed of two or more substances physically mixed, not chemically combined.

Pure Substances: Elements and Compounds

• Element: Composed of one type of atom (e.g., copper (Cu), lead (Pb), aluminum (Al)).

• Compound: Composed of two or more elements always combined in the same proportion (e.g., hydrogen peroxide, H2O2).

Mixtures

• Consist of two or more substances physically mixed in variable proportions.

• Can be separated by physical methods (e.g., filtration, chromatography).

Laboratory Separation of Mixtures

• Filtration: Separates solids from liquids using filter paper.

• Paper Chromatography: Separates components based on their movement through paper.

Homogeneous vs. Heterogeneous Mixtures

• Homogeneous Mixture: Uniform composition throughout; components are not visible (e.g., brass, air, nitrox, heliox, trimix).

• Heterogeneous Mixture: Composition varies; different parts are visible (e.g., water and copper, peach pie).

Classification of Matter – Concept Map

Matter is divided into pure substances (elements and compounds) and mixtures (homogeneous and heterogeneous).

Physical States of Matter

Comparison of Solids, Liquids, and Gases

States of matter differ in shape, volume, particle arrangement, and movement.

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

Physical and Chemical Properties and Changes

Physical Properties

• Observed or measured without changing the substance's identity (e.g., color, state, melting/boiling point, density).

Chemical Properties

• Describe the ability of a substance to interact with or change into other substances (e.g., flammability, reactivity).

Physical Changes

• Changes in state or appearance without altering composition (e.g., melting, boiling, dissolving).

Chemical Changes

• Original substance is converted into one or more new substances with different properties (e.g., burning, rusting).

	Physical	Chemical
Property	Color, shape, melting point, density	Ability to form new substances (e.g., rust, burn)
Change	Change in state or shape	Formation of new substances

Temperature

Temperature Scales

• Measured in Celsius (°C) or Kelvin (K).

• Kelvin scale: no negative values, same unit size as Celsius.

• Conversion: $T_K = T_C + 273$

• Absolute zero: 0 K = -273°C

Energy

Kinetic and Potential Energy

• Kinetic Energy: Energy of motion.

• Potential Energy: Energy due to position or chemical composition.

Heat and Units of Energy

• Joule (J): SI unit of energy. $1 ext{ kJ} = 1000 ext{ J}$

• Calorie (cal): Energy to raise 1 g of water by 1°C. $1 ext{ cal} = 4.184 ext{ J}$ (exact)

• kilocalorie (kcal): $1 ext{ kcal} = 1000 ext{ cal}$

Energy and Nutrition

Food Energy Values

• Carbohydrates: 4 kcal/g (17 kJ/g)

• Fat: 9 kcal/g (38 kJ/g)

• Protein: 4 kcal/g (17 kJ/g)

Energy on food labels is shown as Calories (1 Cal = 1 kcal = 1000 cal).

To calculate energy from food:

• $\text{kilocalories} = \text{g} \times \frac{\text{kcal}}{\text{g}}$

• $\text{kilojoules} = \text{g} \times \frac{\text{kJ}}{\text{g}}$

Energy Requirements and Expenditure

Food Type	kcal/gram	kJ/gram
Carbohydrate	4	17
Fat	9	38
Protein	4	17

Energy needs depend on age, gender, and activity level. Weight loss occurs when energy intake is less than energy output.

Specific Heat

Definition and Formula

• Specific heat ($C_s$) is the amount of heat needed to raise the temperature of 1 g of a substance by 1°C.

• Units: J/g°C or cal/g°C.

• Formula: $C_s = \frac{\text{heat}}{\text{mass} \times \Delta T}$

• For water: $C_s = 4.184 \text{ J/g}^\circ\text{C}$ or $1.00 \text{ cal/g}^\circ\text{C}$

Substance	cal/g°C	J/g°C
Aluminum, Al(s)	0.214	0.897
Copper, Cu(s)	0.0920	0.385
Water, H2O(l)	1.00	4.184

Phase Changes and Energy

Heat of Fusion and Vaporization

• Heat of Fusion: Energy to change 1 g of solid to liquid at melting point (for water: 80 cal/g or 334 J/g).

• Heat of Vaporization: Energy to change 1 g of liquid to gas at boiling point (for water: 540 cal/g or 2260 J/g).

• Formulas:

  • Heat for melting/freezing: $\text{Heat} = \text{mass} \times \text{heat of fusion}$

  • Heat for vaporization/condensation: $\text{Heat} = \text{mass} \times \text{heat of vaporization}$

Summary

• Matter is classified by composition and state.

• Physical and chemical properties and changes are fundamental to understanding matter.

• Energy, temperature, and specific heat are essential for describing and calculating changes in matter.

• Nutrition and metabolism are directly related to chemical energy transformations.