ELEMENTS, COMPOUNDS AND MIXTURES

Q4: Describe the difference between elements, compounds and mixtures. (Cantab Exercise Question).

Elements, Compounds, and Mixtures

Everything around us is either a pure substance or a mixture. Mixtures are impure substances.

Pure Substances: Elements and Compounds

Elements

Elements are the basic building blocks of matter. They cannot be broken down into simpler substances.

Each element is made of identical atoms. There are 115 known elements, with 92 occurring naturally.

Examples: Hydrogen (H), Carbon (C), Oxygen (O), and Iron (Fe).

Compounds

A compound is made of two or more elements combined in a fixed ratio. Example: Water (H₂O) is made of hydrogen and oxygen in a 2:1 ratio by volume.

Mixtures

Mixtures contain two or more substances combined in any proportion. They can be separated using simple lab methods like filtration and distillation.

Types of Mixtures

Homogeneous Mixtures

In a homogeneous mixture, substances are evenly distributed. Examples: Saltwater, air, and sugar dissolved in water.

Heterogeneous Mixtures

In a heterogeneous mixture, substances are not evenly mixed. Examples: Sand and water, milk, and blood.

Comparison Table

PropertyElementCompoundMixture
CompositionOne type of atomTwo or more elementsTwo or more substances
FormulaSymbol (H, O, Fe)Formula (H₂O, CO₂)No fixed formula
SeparationCannot be brokenSeparated by chemical meansSeparated by physical means

Summary

Elements have only one type of atom. Compounds have two or more elements chemically bonded. Mixtures have multiple substances physically combined. Elements and compounds are pure substances, while mixtures are impure.

1. What are elements, and how are they different from compounds and mixtures?

Understanding Matter

When you heat a saturated sugar solution, more sugar dissolves. This is because higher temperature breaks forces between molecules, allowing more sugar to mix in.

Key Points

  • Matter: Anything with mass that takes up space.
  • Plasma: A charged gas affected by electric and magnetic fields.
  • Allotropy: An element’s ability to exist in different forms.
  • Element: The simplest matter, made of identical atoms.
  • Compound: A substance with two or more different atoms bonded together.
  • Solution: A uniform mixture of two or more substances.
  • Aqueous Solution: A solution where water is the solvent.
  • Saturated Solution: A solution that holds the maximum solute at a given temperature.
  • Unsaturated Solution: A solution with less solute than a saturated one.
  • Colloid: A mixture with particles between 1 and 1000 nanometers.
  • Suspension: A mix where solid particles float but don’t dissolve.

Study Resources

Students preparing for FBISE exams can refer to both NBF and Cantab books. These resources ensure comprehensive learning and help in SLO-based exam preparation.

2. Give an example of an element, a compound, and a mixture from everyday life.

Simple Science Facts

Element: Oxygen (O₂) - It's the air we breathe.

Compound: Water (H₂O) - We drink it and cook with it.

Mixture: Salad - A mix of lettuce, tomatoes, cucumbers, and dressing. They are together but not combined chemically.

PlantUML DiagramPlantUML Diagram

Classification of Matter

I. Classification of Matter

A. Pure Substances

  • 1. Elements
  • 2. Compounds

B. Mixtures

  • 1. Homogeneous
  • 2. Heterogeneous
    • a. Colloid
    • b. Suspension

    Colloids, Emulsions, and Suspensions

    1. Colloid

    Definition: A substance with microscopic particles dispersed in a medium, not dissolved.

    Characteristics:

    • Dispersed particles do not settle or form sediment if left undisturbed.

    Example: Pumice (air particles dispersed in solid stone).

    2. Emulsion

    Definition: A specific type of colloid.

    Characteristics:

    • Microscopic particles of liquid dispersed in another liquid.

    Example: Milk (lipophilic butterfat particles dispersed in a water-based medium).

    3. Suspension

    Definition: Similar to a colloid, but with larger dispersed particles.

    Characteristics:

    • Dispersed particles will eventually settle or form sediment.

    Example: Sand in water (when shaken, sand disperses; when left alone, it settles at the bottom).

    ## Key Differences

    • Particle Size:
      • Colloids and Emulsions: Microscopic particles
      • Suspensions: Larger particles
    • Settling Behavior:
      • Colloids and Emulsions: Do not settle
      • Suspensions: Will settle over time
    • Medium:
      • Colloids: Any medium (solid, liquid, or gas)
      • Emulsions: Specifically liquid in liquid
      • Suspensions: Typically solid in liquid

II. Elements

A. Definition

Simplest form of matter made up of the same type of atoms.

B. Characteristics

  • 1. Consist of atoms with the same atomic number (proton number).
  • 2. Cannot be broken down through chemical means.

C. Physical vs. Chemical Changes

  • 1. Physical change: Alters physical properties.
  • 2. Chemical change: Forms a new substance.

III. Compounds

A. Definition

Substance formed when two or more different atoms chemically combine.

B. Key Points

  • 1. Result of a chemical reaction.
  • 2. New substance with properties different from constituent elements.

IV. Mixtures

A. Definition

Substance formed when two or more substances physically combine.

B. Characteristics

  • 1. Does not contain the same types of particles.
  • 2. Particles have different chemical compositions.

C. Example

Tea (combination of milk, water, tea leaves, and sugar).

V. Properties of Matter

  • A. Physical properties
  • B. Chemical properties

Differences Between Compounds and Mixtures

Composition

Compounds have a fixed ratio of elements. Mixtures can have any amount of substances.

Bonding

Compounds have chemical bonds. Mixtures do not have chemical bonds.

Separation

Compounds need chemical reactions to separate. Mixtures can be separated physically.

Properties

Compounds have new properties. Mixtures keep the properties of the original substances.