Pure Substances & Mixtures

CONCEPTUAL

Science›Matter & Materials|Ages 11—13|ID: mt_MBTVB-E-S7

Distinguish between pure substances and mixtures, identify formulations as useful mixtures with precise compositions, and use melting and boiling points to test for purity

Mastery Evidence

Explains why a pure substance has a sharp, fixed melting point but a mixture melts over a range
Identifies common formulations (medicines, alloys, paints, fuels) as deliberate mixtures
Explains what impurities do to melting and boiling points
Distinguishes mixtures from compounds at the particle level

Assessment Prompt

“If [child] was checking whether a sample of water was pure, could they explain one test they could do — and say what result would tell them it was definitely pure versus a mixture?”

Curriculum Standards3 alignments

KS3.Sci.Chem.PIS.1The national curriculum in England

Concept of a Pure Substance

the concept of a pure substance

Science · KS3

KS3.Sci.Chem.PIS.3The national curriculum in England

Identification of Pure Substances

the identification of pure substances: melting and boiling points

Science · KS3

KS3.Sci.Chem.PIS.4The national curriculum in England

Formulations

formulations as useful mixtures

Science · KS3

Prerequisites2

Dissolving & Solutions
hardAges 9—10
Atoms, Elements & Compounds
hardAges 11—12

Show full prerequisite tree

Dissolving & Solutions hard
KS3 purity and formulations extends KS2 dissolving and solutions
- Changes & Separation Vocabulary hard
  Understanding dissolving and solutions requires 'dissolve', 'solution', 'soluble', 'insoluble' from the process vocabulary node
- Advanced Material Properties hard
  Must understand solubility as a property before learning dissolving and recovery in detail
  - Testing Materials for Uses soft
    Within GB sequence, testing advanced properties supports justifying material choices; US teaches material uses earlier without this prerequisite
    - Material Properties Vocabulary soft
      Giving evidence-based reasons for material uses draws on conductor, insulator, and other property vocabulary
  - Material Properties Vocabulary hard
    Grouping materials by hardness, solubility, transparency, conductivity, and magnetic response requires all these property terms
  - Choosing the Right Material hard
    Must understand material suitability before testing advanced properties like conductivity and solubility
    - Material Properties Vocabulary soft
      Comparing suitability of materials for uses requires property vocabulary to articulate why one material is better than another
    - Grouping Materials hard
      Must group materials by properties before evaluating suitability for purposes
      - Describing Material Properties hard
        Must describe properties before using them to group materials
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials
  - Solids, Liquids & Gases soft
    Understanding states of matter supports testing properties like solubility
    - States of Matter Vocabulary hard
      Comparing and grouping materials as solids, liquids, or gases requires the naming vocabulary for the three states
    - Drawing Particle Diagrams hard
      Comparing and grouping solids, liquids, and gases by properties is greatly aided by the particle diagram representation
    - Heating & Cooling Changes hard
      Must classify states of matter before understanding changes between states
      - States of Matter Vocabulary hard
        Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
      - Drawing Particle Diagrams hard
        Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
    - Grouping Materials hard
      Must group materials by properties before classifying into three states of matter
      - Describing Material Properties hard
        Must describe properties before using them to group materials
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials
    - Changing Shapes of Solids soft
      Changing shapes of solids provides context for understanding solid properties
      - Describing Material Properties hard
        Must know material properties before investigating how shapes change
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials
- Evaporation & the Water Cycle soft
  Evaporation knowledge supports understanding recovery of dissolved substances
  - Changes & Separation Vocabulary hard
    Identifying the role of evaporation and condensation requires knowing these process terms precisely
  - The Water Cycle soft
    Water cycle connects to curriculum evaporation/condensation topic
    - Cloud Types hard
      Water cycle requires understanding cloud formation (condensation)
      - Rain & Puddles hard
        Cloud types build on knowing rain comes from clouds
        
        Types of Weather soft
        Rain concept benefits from knowing rain as a weather type
    - Where water is found on Earth soft
      Water cycle benefits from knowing where water is found on Earth
      - Shapes of land and water hard
        Must know land and water features before learning where water is found on Earth
        
        Seasonal changes soft
        Seasonal observation supports understanding land and water features
        
        Days, Weeks, Months & Years soft
        Observing and describing seasonal changes requires basic date and time vocabulary (months, seasons, year)
        
        Ordering Events in Time hard
        Understanding days/months/years builds on sequencing events chronologically
      - Heating & Cooling Changes soft
        Understanding state changes supports knowing water as solid (ice) and liquid
        
        States of Matter Vocabulary hard
        Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
        
        Drawing Particle Diagrams hard
        Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
    - Heating & Cooling Changes soft
      Water cycle benefits from curriculum states of matter (heating/cooling changes state)
      - States of Matter Vocabulary hard
        Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
      - Drawing Particle Diagrams hard
        Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
    - Temperature & Thermometers soft
      Water cycle evaporation relates to temperature (heat drives evaporation)
    - Rain & Puddles hard
      Full water cycle builds on basic rain/puddle/evaporation concept
      - Types of Weather soft
        Rain concept benefits from knowing rain as a weather type
  - Heating & Cooling Changes hard
    Must understand state changes before learning about evaporation/condensation in water cycle
    - States of Matter Vocabulary hard
      Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
    - Drawing Particle Diagrams hard
      Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
Atoms, Elements & Compounds hard
Purity is defined at the atomic/molecular level — distinguishing compounds from mixtures requires atoms/elements knowledge
- The Particle Model hard
  Atoms and molecules are the particles referred to in the particle model — builds directly on it
  - Drawing Particle Diagrams hard
    Using the particle model to explain density, compressibility, and anomalous expansion requires fluent reading and drawing of particle diagrams
  - Matter Is Made of Particles hard
    KS3 particle model extends US KS2 introduction to matter as particles too small to see
    - Drawing Particle Diagrams hard
      Developing a model of matter as particles too small to see is built on the particle diagram representation
    - Heating & Cooling Changes hard
      Must observe state changes before explaining them with particle model
      - States of Matter Vocabulary hard
        Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
      - Drawing Particle Diagrams hard
        Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
    - Solids, Liquids & Gases hard
      Must understand observable states of matter before modelling them with particles
      - States of Matter Vocabulary hard
        Comparing and grouping materials as solids, liquids, or gases requires the naming vocabulary for the three states
      - Drawing Particle Diagrams hard
        Comparing and grouping solids, liquids, and gases by properties is greatly aided by the particle diagram representation
      - Heating & Cooling Changes hard
        Must classify states of matter before understanding changes between states
        
        States of Matter Vocabulary hard
        Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
        
        Drawing Particle Diagrams hard
        Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
      - Grouping Materials hard
        Must group materials by properties before classifying into three states of matter
        
        Describing Material Properties hard
        Must describe properties before using them to group materials
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials
      - Changing Shapes of Solids soft
        Changing shapes of solids provides context for understanding solid properties
        
        Describing Material Properties hard
        Must know material properties before investigating how shapes change
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials
  - Solids, Liquids & Gases hard
    KS3 particle model extends KS2 classification of solids, liquids and gases by observable properties
    - States of Matter Vocabulary hard
      Comparing and grouping materials as solids, liquids, or gases requires the naming vocabulary for the three states
    - Drawing Particle Diagrams hard
      Comparing and grouping solids, liquids, and gases by properties is greatly aided by the particle diagram representation
    - Heating & Cooling Changes hard
      Must classify states of matter before understanding changes between states
      - States of Matter Vocabulary hard
        Describing and measuring changes of state requires solid/liquid/gas vocabulary and the term 'change of state'
      - Drawing Particle Diagrams hard
        Observing and describing change of state requires reading particle diagrams showing how arrangement changes on heating or cooling
    - Grouping Materials hard
      Must group materials by properties before classifying into three states of matter
      - Describing Material Properties hard
        Must describe properties before using them to group materials
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials
    - Changing Shapes of Solids soft
      Changing shapes of solids provides context for understanding solid properties
      - Describing Material Properties hard
        Must know material properties before investigating how shapes change
        
        States of Matter Vocabulary soft
        Describing physical properties of materials uses solid/liquid/gas vocabulary introduced in the states of matter LANGUAGE node
        
        Naming Everyday Materials hard
        Must name materials before describing their properties
        
        Objects vs Materials hard
        Must distinguish objects from materials before naming specific materials

Unlocks1

Separating Mixtures
hardAges 11—13