Chemical Properties of Materials
Chemical Properties
A chemical property is a characteristic of a material that only becomes noticeable during or after a chemical reaction.
Choosing materials with the appropriate chemical properties is essential in industries like food production, construction, aerospace, and consumer electronics, where exposure to heat, moisture, or chemicals can lead to failure or safety risks.
Key Chemical Properties
- Corrosion Resistance
- Reactivity (Food Safe)
- Hygroscopy
- Flammability
Corrosion Resistance
Corrosive Resistance
The ability of a material to resist damage caused by oxidation (like rust) or other chemical reactions with substances such as water, acids, or salts.
Factors Affecting Corrosion Resistance
- Material Composition: Stainless steel contains chromium, which forms a protective oxide layer.
- Environmental Conditions: High humidity and salt increase corrosion rates.
- Protective Coatings: Paints or galvanisation can prevent exposure to corrosive elements.
- Ferrous metals contain iron, which makes them more susceptible to corrosion, especially when exposed to moisture and oxygen.
- As a result, they generally have low corrosion resistance.
- Stainless steel is an exception to this rule, it is a ferrous metal and contains a significant amount of iron, however, its chromium content gives it its corrosion-resistant properties.
| Ferrous Metals | Non-Ferrous Metals |
|---|---|
| Mild Steel | Aluminum |
| Cast Iron | Copper |
| Carbon Steel | Brass |
Stainless steel's corrosion resistance makes it suitable for kitchen appliances and medical instruments.
Reactivity (Food Safe)
Reactivity (food safe)
A chemical property that describes how likely a material is to react with food, air, or cleaning chemicals in a way that could make it unsafe for food contact.
Key Considerations
- Non-Toxicity: Materials must not leach harmful substances.
- Chemical Stability: They should resist reacting with acids, bases, or other food components.
- Regulatory Standards: Compliance with food safety regulations is essential.
- Stainless steel: Low reactivity, safe for cooking and food storage.
- Aluminum: Can react with acidic foods (like tomatoes), so it’s often coated.
- Copper: Highly reactive—must be lined with a non-reactive material when used in cookware.
Hygroscopy
Hygroscopy
A chemical property that describes a material’s ability to absorb moisture from the surrounding air.
Implications of Hygroscopy
- Material Degradation: Absorbed moisture can lead to swelling, warping, or weakening.
- Electrical Conductivity: Increased moisture can affect the electrical properties of materials.
- Storage and Handling: Hygroscopic materials require controlled environments to maintain their integrity.
- Wood: Absorbs moisture, which can cause warping or swelling.
- Nylon: Can absorb water, affecting its strength and flexibility.
- Salt and sugar: Clump together when exposed to air due to moisture absorption.
Flammability
Flamability
A measure of how easily and quickly a material can be ignited and how fast it burns once on fire.
Factors Influencing Flammability
- Chemical Composition: Materials with high carbon content are often more flammable.
- Surface Area: Finer particles or thinner materials ignite more easily.
- Environmental Conditions: Oxygen levels and temperature affect flammability.
- Cotton fabric: Highly flammable, often treated with flame retardants.
- Polyester: Burns but melts first, which can cause burns.
- Fire-retardant foam: Designed to resist ignition and slow down burning.
State one chemical property that is relevant to the selection of bamboo as the material for bamboo coffee cup. (1 mark)
Solution
Answers may demonstrate:
Award [1] for stating one of the listed terms below that would be used for chemical property of the material of the coffee cup up to [1 max]
- Reactivity
- Hygroscope
