Chemistry Unit 1 Homework

Study Notes

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).

Description

This homework covers classifications of substances and mixtures in chemistry, focusing on pure substances, elements, and compounds. You'll classify various examples and identify pure elements from a list. Test your understanding of chemistry fundamentals with this assignment!