Student Learning Outcomes (SLOs)
- Explain the properties of different materials and how they can be applied to desired structures.
- Explain the process of extracting material from ores and alloying them to achieve desired characteristics.
- Explain the mechanism of catalysts and how they increase the rate of a reaction while remaining unchanged at the end.
- Explain the challenges associated with recycling and toxicity of some materials produced through materials science.
- Explain the use of X-rays crystallography in analyzing structures.
Quick Tip
Think of materials science as the study of “stuff” – everything around us is made of materials, and understanding their properties helps us create better products and technologies.
20.1 MATERIALS
A material is a substance or mixture that makes up an object. Everything around us is made from materials, each with unique properties. The materials can be soft or hard, flexible or stiff, and delicate or strong. Material can be used to describe something that is made of matter and exists in the physical world. There are many different types of materials. Some common examples of everyday materials are plastics, metals, fabric and glass.
Interesting Fact
Graphene is one of the strongest materials known. It conducts heat better than diamond, and may conduct electricity better than silver. As it’s two-dimensional, it could be used to detect single molecules of a gas if a gas molecule were to stick to a sheet of graphene there would be a local change in the electrical resistance.
20.1.1 Properties of Material
The properties of materials such as strength, flexibility, heat and electrical conductivity and melting and boiling points are key factors that determine how materials can be used. These properties are influenced by the material’s chemical composition and internal structure.
Memory Aid
Remember: Material properties determine their applications. Think of it as matching the right tool for the job – you wouldn’t use glass to build a bridge or concrete to make windows!
20.1.2 Alloys and Metal Compounds
Properties like shape and mass may be different for different objects even when they are made of the same material. Density is a useful property for making comparisons between different materials. Mixtures of metals called alloy is common example. By alloying some of the important properties of metals can be improved. Metals can be produced (smelted) from their ores by a variety of methods.
Fun Facts
Many alloys that contain silver in their name usually do not contain silver as one of their constituent elements. They are called ‘silver’ only because of their color. Examples of this are Tibetan silver and German silver.
Stainless steel is formed by mixing iron, small quantities of carbon and chromium is called ‘stainless’ because chromium gives it resistance from any kind of stain or iron rust.
Alloys Properties
- Stronger than constituent metals
- Harder than constituent metals
- More resistant to corrosion
- Lower melting points
- Lower electrical conductivity
- Malleable and ductile
Plastics Properties
- Low density
- Chemically inert
- Good insulators
- Easily molded
- Lightweight
- Low cost
Ceramics Properties
- Very hard
- Brittle
- Comparable strength to metals
- Poor heat/electricity conductors
- Various transparency levels
Click to Reveal: Material Selection Tips
- Strength & Weight: Aerospace applications need strong, lightweight materials like titanium alloys
- Corrosion Resistance: Marine environments require stainless steel or specialized coatings
- Thermal Properties: Engine components need materials that can withstand high temperatures
- Electrical Conductivity: Electronics need good conductors (copper) and insulators (plastics)
- Cost Considerations: Balance performance requirements with budget constraints
20.2 EXTRACTING MATERIAL FROM ORES AND ALLOYING
How DOES REACTIVITY AFFECT EXTRACTION?
The reactivity of a metal determines how it is extracted.
Memory Aid
Remember: The reactivity series determines extraction methods. Highly reactive metals (like sodium, potassium) require electrolysis, while less reactive metals (like copper, silver) can be extracted by simple heating or reduction.
Extraction Process Steps:
- Extraction: Crushing, grinding, and concentration of ores
- Roasting: Heating in air to convert to oxides
- Smelting: Reducing metal ions to free metal using reducing agents
- Refining: Purification of metals through electrolysis or distillation
- Alloying: Combining metals with other elements to enhance properties
2ZnS(s) + 3O₂(g) → 2ZnO + 2SO₂(g)
Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)
Extraction Tip
The Bessemer converter process is crucial for steel production. It removes impurities from iron by blowing air through molten iron, oxidizing unwanted elements like carbon, silicon, and phosphorus.
Quick Quiz
20.3 MECHANISM OF CATALYSTS
20.3.1 What is Catalysis?
Catalysis is process when the speed of a chemical reaction is altered by a substance called a catalyst. This catalyst is not used up in the reaction and can be used over and over again. Usually, even a small amount of catalyst is enough to speed up the reaction.
Memory Aid
Remember: Catalysts are like matchmakers – they bring reactants together but don’t get “married” themselves. They lower the “energy barrier” (activation energy) for reactions to happen.
20.3.2 Mechanism of Catalysis
Transition metals make excellent catalysts as they have incompletely filled d-orbitals that allow them to both donate and accept electrons easily from other molecules.
Real-World Catalyst Application
Catalytic converters in cars use platinum, palladium, and rhodium to convert harmful exhaust gases (CO, NOx, hydrocarbons) into less harmful substances (CO₂, N₂, H₂O). This has dramatically reduced air pollution from vehicles.
2H₂O₂ → 2H₂O + O₂
Catalyst: MnO₂
Click to Reveal: Types of Catalysis
- Homogeneous Catalysis: Catalyst and reactants are in the same phase (e.g., acid catalysis in solution)
- Heterogeneous Catalysis: Catalyst and reactants are in different phases (e.g., solid catalyst with gaseous reactants)
- Enzyme Catalysis: Biological catalysts (enzymes) that speed up biochemical reactions
- Autocatalysis: Reaction product acts as a catalyst for the same reaction
20.4 CHALLENGES ASSOCIATED WITH RECYCLING
The recycling problem involves challenges in collecting, sorting, managing, and processing recyclable materials. These problems arise due to factors like poor waste management systems, improper waste disposal, lack of education and lack of awareness about recycling, and difficulty in separating recyclable from non-recyclable waste.
Amazing Recycling Facts
Recycling one glass bottle saves enough energy to light a 100-watt bulb for four hours. Recycling one aluminum can saves enough energy to run a 55-inch HDTV to watch your favorite movie.
Each ton (2,000 pounds) of recycled paper can save 17 trees, 380 gallons of oil, three cubic yards of landfill space, 4,000 kilowatts of energy, and 7,000 gallons of water.
Main Recycling Challenges:
- Complex Material Composition: Modern materials often consist of multiple layers or composites
- Contaminants and Purity Issues: Materials contaminated with substances like oils or adhesives
- Economic Viability: Recycling processes often more expensive than producing new materials
- Environmental and Health Risks: Toxic substances in some materials pose risks if not properly managed
- Technological Limitations: Current technologies may not efficiently process certain materials
Recycling Tip
Always check your local recycling guidelines. What’s recyclable in one area might not be in another. Proper sorting at home makes the recycling process more efficient and cost-effective.
20.5 X-RAY CRYSTALLOGRAPHIC ANALYSIS
X-ray crystallography is a method that uses X-rays to find out the detailed structure of a crystal, including the arrangement of its atoms and molecules. This helps us understand how these atoms and molecules are bonded and any irregularities in the crystal.
Historical Achievement
X-ray crystallography was crucial in discovering the double-helix structure of DNA by Franklin, Watson, and Crick in 1953 – one of the most important scientific discoveries of the 20th century.
20.5.1 Applications of X-ray Crystallography
- Understanding 3D structures of proteins and biomolecules
- Determining structures of DNA and RNA
- Drug discovery and development
- Material science and nanotechnology
- Structural determination of complex compounds
- Geological studies and mineral analysis
- Environmental science applications
Memory Aid
Remember: X-ray crystallography is like taking a “molecular photograph” – it reveals exactly how atoms are arranged in a crystal, helping us understand material properties at the atomic level.
KEY POINTS
- Each item is made up of various materials and when one substance is mixed with another, it creates a unique material with specific qualities.
- Homogeneous mixture formed by mixing metal with other metal or nonmetals in a certain proportion is called an alloy.
- By making alloys some of the important properties of metals can be improved.
- Recycling is the process of collecting, processing of materials that would otherwise be discarded as waste, converting them into new products.
- The toxicity of materials produced through recycling can vary significantly depending on the type of material and the recycling process used.
- A catalyst provides an alternate pathway for the reaction that has a lower activation energy. When activation energy is lower, more reactant particles have enough energy to react, so the reaction occurs faster.
- X-ray crystallography uses electromagnetic radiation (specifically, X-rays) to determine the molecular and atomic structure of a crystal.
- X-ray crystallography is a technique used to determine the atomic and molecular structure of a crystal by measuring the angles and intensities of X-rays diffracted through the crystal lattice.
- X-ray crystallography provides detailed information about the arrangement of atoms within the crystal, crucial for understanding the structure and function of various materials, including biological molecules like proteins.
ACTIVITY: Poster Design on Recycling
Objective:
To educate students about the importance of recycling and to encourage them to creatively express their knowledge and ideas through poster design.
Groups:
Divide the class into small groups of 3-4 students. Assign each group a specific aspect of recycling to focus on (e.g., plastic recycling, electronic waste, composting etc.).
Poster Requirements:
- Clear message about the importance of recycling
- Visual elements that attract attention
- Facts and statistics about recycling
- Practical tips for better recycling habits
- Creative and original design
Activity Tip
For an impactful poster, focus on one key message. Use bold colors and minimal text. Include a clear call to action that tells viewers what they can do to improve recycling in their community.