Chemistry in Context Lecture Notes
What’s the Matter with Materials?
Introduction to Matter
- Definition of Matter:
- Matter is defined as anything that occupies space and has mass. Everything around us can be classified as matter.
Classification of Matter
Classification by Phase:
Phase Takes the shape of its container? Completely fills its container? Definite volume? Definite shape? Solid No No Yes Yes Liquid Yes No Yes No Gas Yes Yes No No Interactive Activity:
- Engage with simulations showing atoms and molecules in different states of matter.
Types of Matter by Composition
- Pure Substances:
- Elements:
- Comprised solely of one type of atom (e.g., silicon - Si).
- Compounds:
- Composed of two or more different types of atoms bonded together (e.g., silicon dioxide - SiO₂).
- Mixtures:
- Heterogeneous Mixtures:
- Composition varies throughout (e.g., gravel).
- Homogeneous Mixtures:
- Uniform composition throughout (e.g., sugar solutions in water).
Physical and Chemical Properties
Physical Process:
- A transformation that does not alter the chemical identity of substances involved (e.g., a change in state).
Physical Change:
- Occurs when a substance's physical appearance changes, but its chemical composition remains constant.
- Examples:
- Water melting.
- Salt dissolving in water.
Chemical Change:
- Involves a change in the substance's chemical composition.
- Example:
- Ignition of gasoline:
Characteristics of Pure Substances
- Defined as made up of one type of particle and have invariant composition.
- Properties are consistent throughout; cannot be separated into simpler substances by physical means.
- Examples:
- Helium (He), water (H₂O), sodium chloride (NaCl).
Classification of Mixtures
- Mixtures consist of two or more pure substances and can be separated by physical processes.
- They can vary in composition from one sample to another.
- Homogeneous Mixtures:
- Uniform distribution, no visible boundaries (e.g., sweetened tea).
- Heterogeneous Mixtures:
- Non-uniform distribution, may show distinct regions (e.g., water and sand).
Example Classification of Matter
- Examples:
- Carbon Dioxide: Compound
- Nickel: Element
- Sugar: Compound
- Water: Compound
- Fluorine: Element
- Table Salt: Compound
- Soap: Mixture
- Sea Water: Mixture
The Periodic Table
- Composed mainly of metals; metalloids include: B, Si, Ge, As, Sb, Te, Po.
- Categories of Elements:
- Metals:
- Shiny solids, conduct heat and electricity, malleable and ductile.
- Nonmetals:
- Solids, liquids, and gases that are nonconductor, and brittle in solid form.
- Metalloids:
- Have properties of both metals and nonmetals, are semiconductors.
Groups of the Periodic Table
- Notable Groups:
- Group 1: Alkali Metals
- Group 2: Alkaline Earth Metals
- Group 15: Pnictogens
- Group 16: Chalcogens
- Group 17: Halogens
- Group 18: Noble Gases
Chemical Symbols
- Chemical symbols are typically 1 or 2-letter abbreviations for elements.
- Examples:
- O: Oxygen
- Si: Silicon
- Pb: Lead (Plumbum in Latin)
- Hg: Mercury (Hydrargyrum in Greek)
- Cu: Copper (Cuprum in Latin)
- Fe: Iron (Ferrum in Latin)
- K: Potassium (Kalium in Latin)
- Sb: Antimony (Stibium in Latin)
- Ag: Silver (Argentum in Latin)
- Au: Gold (Aurum in Latin)
From Elements to Compounds
- Elements combine in integer ratios to form compounds with different properties.
- Examples:
- Iron (Fe)
- Iron (III) Oxide (Fe₂O₃)
- Magnetite (Fe₃O₄)
Atom Structure
- Atoms are the smallest building blocks of matter and are made of subatomic particles: protons, neutrons, and electrons.
- Components:
- Protons and neutrons are in the nucleus; electrons orbit.
| Particle | Relative Charge | Relative Mass | Actual Mass (kg) |
|---|---|---|---|
| Proton | +1 | 1 | $1.67 imes 10^{-27}$ |
| Neutron | 0 | 1 | $1.67 imes 10^{-27}$ |
| Electron | -1 | 0 | $9.11 imes 10^{-31}$ |
- For neutral atoms, the number of electrons equals the number of protons to balance charge.
- Example Atoms:
- Hydrogen: Atomic #: 1 (1 proton) Mass #: 1.
- Helium: Atomic #: 2 (2 protons, 2 neutrons) Mass #: 4.
Importance of Recycling
- Average cell phones contain significant amounts of valuable metals:
- 300 mg of silver.
- 30 mg of gold (30 times denser than in gold ore).
- Urban Mining:
- Refers to recycling electronics to recover valuable metals.
- Some companies are developing robotic disassembly to enhance safety and environmental sustainability.
Rare Earth Metals
- Rare earth metals are critical for various applications, such as:
- Rechargeable batteries
- Magnets
- Speakers
- Memory chips
- Fluorescent lighting
- Catalytic converters
- Advanced electronics and weaponry
- Global Supply:
- China dominates the production of rare earth metals, controlling over 90% of the global supply with 50% of the world's reserves.
Questions for Reflection
- Your Turn Activities:
- Analyze atomic structures and identify protons and electrons in several elements.
- Discuss the implications of electronic waste and urban mining on the environment.