Study Notes on Pure Substances, Mixtures, and Properties of Matter
Pure Substances
Definition: Made up of only one type of particle.
Every sample has the same, uniform composition.
Elements
Definition: Composed of only one type of particle.
Examples:
Hydrogen (H₂)
Oxygen (O₂)
Calcium (Ca)
Molecular Elements:
There are 7 molecular elements referred to in the mnemonic: Have No Fear Of Ice Cold Beer:
Hydrogen
Nitrogen
Fluorine
Iodine
Chlorine
Bromine
Molecular Compounds
Definition: Comprises two different elements bound together chemically.
Example: Water (H₂O) which is made up of more than one type of element.
Mixtures
Definition: Composed of two or more different types of particles.
Types of Mixtures
Homogeneous Mixture (Solution)
Different types of particles combine to appear as a pure substance.
Examples:
Salt water
Apple juice
Air
Pool water
Heterogeneous Mixture (Mechanical Mixture)
Distinct, easily distinguished components.
Examples:
Cereal
Soil
Salad
Mud
Suspension: Small particles suspended in another substance.
Alloys
Definition: Mixture of two or more metals that are mixed together physically, classified as homogeneous.
Method of Creation: Made by melting down pure metals and physically mixing them together to create a solution.
Qualitative vs. Quantitative Observations
Qualitative Observations
Definition: Observations of substances that are not measured.
Details:
Characteristics include color, odour, and texture.
Quantitative Observations
Definition: Observations of substances that are measured, possessing numerical values.
Details:
Examples include height, mass, etc.
Physical Properties
Definition: Characteristics we can assess about a substance without altering its chemical composition.
Categories of Physical Properties
State:
Describes how fast particles are moving, classified as solid, liquid, or gas.
Taste:
Sensation of flavour; may include sweet, bitter, sour, etc.
Texture:
Visual and tactile quality of a surface; categorized as silky, rough, slimy, etc.
Examples of Physical Properties
Luster:
The shininess or dullness of a surface.
Example: A mirror is very lustrous, having a high degree of luster.
Optical Clarity:
Ability of a substance to allow light to pass through.
Classification: Transparent, translucent, opaque.
Hardness:
Relative ability of a substance to scratch or be scratched.
Example: Diamonds possess a high hardness.
Conductivity:
Ability of a substance to conduct electricity.
Example: Copper and wires of other types are electrically conductive.
Additional Physical Properties
Malleability:
Ability of a material to be hammered into thinner sheets.
Ductility:
Ability of a material to be pulled into finer strands.
Brittleness/Flexibility:
Describes how easily a material bends;
Not bendable = rigid;
If a material bends and returns to its original shape, it is elastic.
Solubility:
Ability of a solute to dissolve in a solvent.
Example: Salt (solute) dissolves in water (solvent).
Viscosity:
Measure of a substance's resistance to flow.
Example: Honey is more viscous than water; greater resistance correlates to greater viscosity.
Changes in Matter
Physical Change
Definition: The composition of a substance remains unaltered.
Examples:
Ice cube melting into water
Paper transforming into a paper airplane.
Chemical Change
Characteristics: Always results in the formation of one or more new substances.
Evidence of a Chemical Change
Change in Colour:
Indicates a new substance has formed that has a different colour than the original substance.
Change in Odour:
A new substance has formed that produces a detectable odour.
Production of Gas:
New substances generated in the form of gas, often visible in bubbles that are not due to heating.
Change in Temperature or Light:
Observable evidence of a chemical change.
Formation of Precipitate:
Solid that forms from a solution during a chemical reaction.