Chemistry

• Physical change:

  • Does not change the way the atoms link up
  • Substance may look different but no new substance has been formed
  • Chemical properties are not changed
  • No energy taken in or given off unless there is a change of state
• Examples of physical changes:

  • Ice melts
  • Wax hardens on a candle
  • Paper is shredded
• Chemical change:

  • Matter changes from one kind of material to another
  • Atoms that make up the material do not change but instead change the way they link up
  • New substances can have very different properties than old substance
  • Energy is always either taken in or given off
• Examples of chemical changes:

  • A cake is baked
  • Iron rusts
  • Sulphur is burned
• In a chemical change, the original substance is changed into a different substance that has different properties
• Evidence of a chemical change:

  • Change in color
  • Energy is released or absorbed
  • Gas is released
  • A precipitate is formed
  • The change is difficult to reverse
  • A new scent is released
• Chemical property:

  • A characteristic of a substance that is determined when the composition of the substance is changed and one or more new substances are produced
• Examples of chemical properties:

  • Combustibility
  • Reactivity with other substances
  • Sensitivity to light
• Quantitative properties:

  • Burns at 233°C
• Qualitative properties:

  • Melts at -12°C
  • Smooth texture
  • Dissolves in water at 50°C
  • Resistant to acid
• Chemistry is the study of matter, its properties, and the changes that matter undergoes
• Matter is everything that has mass and takes up space
• Particle Theory of Matter:

  • All matter is made up of tiny particles with empty space between them
  • Different substances are made up of different kinds of particles
  • Particles are in constant movement and move faster as the temperature increases
  • Particles attract each other, especially of things that substance A and substance B
• Physical properties of matter:

  • Hardness: a measure of resistance of a solid to being scratched or dented
  • Ductility: the ability of a substance to be pulled into thin wires
  • Malleability: the ability of a solid to be hammered or bent into different shapes
• Quantitative properties are measured and have a numerical value, while qualitative properties are not measured and do not have a numerical value
• Solubility: the ability of a substance to dissolve in a solvent, usually water
• Viscosity: how easily a liquid flows, increasing as the thickness of the liquid increases
• Density: the amount of matter per unit volume of that matter, calculated as Density (D) = Mass (M) / Volume (V)
• Transparency: the ability of a substance to allow light through, categorized as transparent (e.g., glass), translucent (e.g., frosted glass), or opaque (e.g., brick wall)
• Taste, smell, and texture are sensory properties of matter
• Brittleness: the ability of a substance to break apart, crumble, or shatter easily
• Color: the property that describes what color an object is
• Electrical conductivity: the ability of a substance to allow electrical conductivity to pass through it
• Mass: the amount of matter an object has, measured in grams (g) or kilograms (kg)
• Volume: the amount of space something takes up, measured in millimeters (ml), liters (L), or if solids, in cubic centimeters (cm3)
• Lustre: the ability of a substance to reflect light
• Density units: kg/m², g/cm², g/ml, g/L
• State differences between compounds and solutions, compounds and elements, and solutions and heterogeneous mixtures
• Classification of Matter:

  • Mixtures: a combination of pure substances, categorized as mechanical mixtures (heterogeneous) or solutions (homogeneous)
  • Pure substances: categorized as colloids, compounds, elements, or alloys
• Evidence of a chemical change: 1. A change in color occurs 2. Energy is released or absorbed (heat/light is given off) 3. Gas is released 4. A precipitate is formed 5. The change is difficult to reverse 6. A new scent was released
• Chemical Changes


  • In a chemical change, the original substance is changed into a different substance that has different properties, The particles in the new substance are different from the original ones, It is a change in matter in which at least one substance with new properties
• Chemical change


  • Change in appearance, New substance(s) formed, Chemical properties do not change
• Optical Clarity


  The ability to allow light through
• Texture

  How an object feels
• Density


  The amount of matter per unit volume of that matter
• Odor


  How an object smells
• Electrical Conductivity


  The ability of a substance to allow electrical conductivity to pass through it
• Chemical Property


  • Is a characteristic of a substance that is determined when the composition of the substance is changed and one or more new substances are produced
• Mass

  The weight an object has
• Ductility


  The ability of a material to stretch without breaking