Questions and Answers
Which classification describes HCl (aq)?
What type of substance is a diamond?
Which of the following is true regarding the identity of a pure substance when it is melted or frozen?
What is an example of an extensive property of an iron nail?
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Which substance is a solid at -50°C?
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What happens to oxygen as it is cooled from -150°C to -200°C?
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Which state of matter are particles closest together?
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Which of the following substances condenses from a gas to a liquid as the temperature drops from 20°C to -50°C?
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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).
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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!
