chemistry

• Matter is anything that has mass and occupies space
• Mass refers to the amount of matter present in a sample
• Matter is composed predominantly of atoms consisting of protons, neutrons, and electrons
• Matter includes all things - both living and nonliving, as well as naturally occurring and manmade
• Various forms of energy such as heat, light, and electricity are not considered to be matter
• All matter is made of tiny particles
• Particles in matter are in constant motion
• The speed of particles is proportional to temperature; increased temperature means greater speed
• Solids, liquids, and gases differ in distances between particles, freedom of motion of particles, and the extent to which the particles interact
• Physical properties of matter can be observed with senses or measured without changing the identity of the matter
• Physical properties of matter include mass, volume, molecular weight, state, hardness, color, odor, boiling point, melting point, ductility, malleability, texture, thermal and electrical conductivity, magnetism, opacity, luster, transparency, solubility, density, viscosity, elasticity, brittleness, volatility, and crystal form
• Density of a substance is defined as the total mass divided by its total volume
• Solubility is the ability of a substance to dissolve in a given amount of solvent
• Some substances are attracted to magnets, while others are not
• The boiling point of a liquid is the temperature at which it is converted into a gas
• Metals are good conductors of electricity, while nonmetals do not conduct electricity easily
• When substances are heated, they respond in different ways
• A physical change is a process in which a substance changes its physical appearance but not its chemical composition
• A chemical change is a process in which a substance undergoes a change in chemical composition
• Matter can be classified in terms of its chemical composition
• A pure substance is a single kind of matter that cannot be separated into other kinds of matter by any physical means
• A mixture is a physical combination of two or more pure substances in which each substance retains its own chemical identity
• Elements:

  • Cannot be broken down into simpler pure substances by any chemical means such as chemical reactions, an electric current, heat, or beam of light
• Compounds:

  • Can be broken down into two or more simpler pure substances by chemical means
• Homogeneous mixture:

  • Contains only one visibly distinct phase (part), which has uniform properties throughout
• Heterogeneous mixture:

  • Contains visibly different phases (parts), each with different properties
• Compounds have properties distinctly different from those of the substances that are combined to form the compounds. The components of mixtures retain their individual properties
• Compounds have a definite composition, while mixtures have a variable composition
• Physical methods are sufficient to separate the components of a mixture, while the components of a compound cannot be separated by physical methods; chemical methods are required
• Examples of mixtures:

  • Salt and sugar
  • Oil and water
  • Sand, stones, and pebbles
  • Smoke and fog (Smog)
  • Dirt and water (Mud)
  • Sand, water, and gravel (Cement)
• Methods to separate mixtures:

  1. Hand sorting:

  • Substances in a mixture can be separated by picking them out by hand from the mixture
  • Carried out in dry conditions
  • Example: Sorting stones and seeds

  2. Sieving:

  • Separates components based on the difference in their sizes using sieve plates

  3. Filtration:

  • Separates an insoluble solid from a liquid
  • The solid remains in the filter paper while the liquid passes through

  4. Magnetic separation:

  • Separates components of mixtures using magnets to attract magnetic materials

  5. Evaporation:

  • Separates a soluble solid from a liquid by driving off the liquid components

  6. Distillation:

  • Separates components based on different boiling points
  • Effective for mixtures of two or more pure liquids with different boiling points

  7. Chromatography:

  • Suitable for separating different colored dyes by their solubility
• Activity Time!

  • Determine the method of separation to be used:

  1. Flour and rice - Sieving

  2. Paperclips and sawdust - Magnetic separation

  3. Peanuts, almonds, and Nips chocolate - Hand sorting
• Chemical formula:

  • Notation made up of chemical symbols of elements in a compound and numerical subscripts indicating the number of atoms of each element in a molecule of the compound
• Molecular formula:

  • Consists of chemical symbols for the constituent elements followed by numeric subscripts describing the number of atoms of each element present in the molecule
• Empirical formula:

  • Represents the simplest whole-integer ratio of atoms in a compound
  • The molecular formula can be the same as or a multiple of the compound’s empirical formula
• Empirical formula:

  • Expressed as the smallest whole number ratio of atoms in a compound
  • Example: Determine the empirical formula for dioxin (C12H4Cl4O2) as C6H2Cl2O
• Empirical formula:

  • Involves finding the moles of each element in a compound
  • Deriving the molar ratio between elements by dividing by the lesser number of moles
  • Multiplying the ratio by two to obtain the smallest whole number subscripts while maintaining the correct ratio
• Structural formula:

  • Indicates not only the number of atoms but also their arrangement in space