Chemistry Unit 1 Homework

Pure Substances and Mixtures

• HCl (aq): classified as a homogeneous mixture.
• C11H22O11 (s): identified as a pure substance and specifically a compound.
• KBr (s): recognized as a pure substance and a compound.
• Soil: categorized as a heterogeneous mixture.
• Cl2 (g): identified as a pure substance and an element.
• CH2(OH)2 (aq): classified as a homogeneous mixture (assuming aqueous solution).
• Na (s): recognized as a pure substance and an element.

Pure Substances - Elements and Compounds

• Diamond: is a pure substance and specifically classified as an element.
• Quartz crystals: are classified as a pure substance and specifically a compound.
• Ocean water and vanilla ice cream are not pure substances since they consist of mixtures.

Properties of Pure Substances

• A pure substance's identity remains unchanged during melting or freezing, confirming the concept of its physical state.

Water vs. Milk

• Water is a pure substance due to its uniform composition, while milk is considered a mixture because it contains suspended particles and varying components.

Physical Properties of Silver

• Common properties include shininess (luster), conductivity (thermal and electrical), and malleability (ability to be shaped).

Extensive vs. Intensive Properties

• Extensive property example: Mass of an iron nail, which varies based on the amount of iron.
• Intensive property example: Density of an iron nail, remains constant regardless of size.

Particle Arrangement in States of Matter

• Solid: particles are tightly packed in a fixed arrangement.
• Liquid: particles are close together but can move freely.
• Gas: particles are far apart and move independently.

Vapor vs. Gas

• Gasoline in gaseous form can be referred to as vapor, as vapor typically describes the gaseous state of substances that are liquid or solid at room temperature.

Physical Changes

• Sharpening a pencil involves physical change (removal of material), whereas dissolving sugar in water results in a homogeneous mixture, a different kind of physical change.

Physical States at Room Temperature

• Oxygen: gaseous state.
• Iron: solid state.
• Mercury: liquid state.

Physical Changes in Different Instances

• Cooling oxygen from -150°C to -200°C is a physical change (condensation).
• Cooling iron from 1600°C to 1500°C also accounts for a physical change (solid phase change).
• Heating mercury from -130°C to -100°C is a physical change (melting).

Substances Under Specific Conditions

• Substance that is solid at -50°C: Specific identification needed (not provided).
• Liquid at 1000°C: Specific identification needed (not provided).
• Substance that condenses from gas to liquid between 20°C to -50°C: Specific identification needed (not provided).