SNC2D Grade 10 Science – Chemistry Notes

 

Unit 2 Atoms, Elements, and Compounds

Safety-Don’t do anything stupid

Sig digs

  • 2400 has an assumed 4, but is actually infinite
  • Conversions are always infinite
  • Use scientific notation if you have to, but keep the required sig digs
  • When calculating, the answer must have the same amount of sig digs as the number with the fewest (e.g. 90.4-10.43=80) so round

Density

  • Is mass/volume
  • GRASS (given, Required, analysis, solve, statement)

PTM (Particle theory of matter)

  1. All matter is made out of particles
  2. Particles of the same substance are identical
  3. All particles have spaces between them
  4. Particles are constantly in motion
  5. Heat affects the speed at which particles move
  6. There are forces of attraction between particles

Gas Tests

  • For oxygen, insert a glowing splint into the mouth of the container of gas, if it bursts into flames, then it is oxygen
  • For Hydrogen, insert a burning splint into the mouth of the container, if the splint goes out with a popping noise, then it is hydrogen
  • For Carbon dioxide, bubble the gas with limewater, if it becomes cloudy, then it is carbon dioxide
  • For H2O (water), if the cobalt chloride (CoCl2) changes colour from blue to pink, then it is water

Mass of Sub-Atomic Particles

  • Electrons-1
  • Protons-1836
  • Neutrons-1837

In order to test the conductivity of a substance, use a conductivity apparatus.

Mixtures and Pure Substances

  • Pure substances include compounds and elements
  • Elements are found in the periodic table (e.g. Hydrogen-H)
  • Compounds are two or more elements joined together by a bond in a fixed ratio (e.g. H2O)
  • Pure substances are homogeneous (uniform throughout)
  • Mixtures include homogeneous and heterogeneous
  • Homogeneous mixtures are either solutions or alloys
  • Alloys are metal (e.g. bronze, the nickel coin, steel)
  • Solutions (e.g. sugar and water) involve the solute and the solvent
  • Heterogeneous mixtures are colloids, ordinary mechanical mixtures, emulsions, or suspensions
  • Suspension-when one substance sinks to the bottom cuz it’s denser-e.g. muddy water
  • Emulsions-when the two liquids refuse to mix (e.g. oil and water)-when your otp doesn’t even like each other
  • Colloid-when the particles are too smol that even gravity can’t break them up (too adorable) e.g. milk
  • Ordinary mechanical mixture-literally everything else e.g. granite
  • The Tyndall effect is how to tell colloids and solutions apart, if light is scattered by the particles, then it is a colloid
  • Homogeneous mixtures appear uniform throughout whereas heterogeneous mixtures consist of visibly different substances

Properties of Matter

  • Physical properties are those that can be observed (qualitative) or measured(quantitative)
  • Chemical Properties describe how a substance reacts to another substance

Evidence for Chemical Changes

  1. Heat is produced
  2. A precipitate(solid that forms when 2 solutions are combined) forms
  3. Change in odor
  4. Starting material is used up (consumed)
  5. Heat is absorbed (gets colder)
  6. Change in colour
  7. Effervescence

Evolution of the Atom

Democritus

  • Greek philosopher, father of modern atomic thought.
  • Proposed that matter could NOT be divided into smaller pieces forever.
  • Claimed that matter was made of small, hard particles that he called “atomos”

John Dalton

  • Created the very first atomic theory.
  • Viewed atoms as tiny, solid balls.
  • Theory consisted of four statements
    • Atoms are tiny, indivisible particles.
    • Atoms of one element are all the same.
    • Atoms of different elements are different.
    • Compounds form by combining atoms.

J.J. Thomson

  • Discovered electrons.
  • Proposed the existence of  protons
  • His atomic model was known as the “raisin bun model” or “plum pudding model”
  • First scientist to show that the atom was made of even smaller things.

Ernest Rutherford

  • Discovered protons and the nucleus.
  • Showed that atoms have (+) particles in the center, and are mostly empty space.
  • He called the center of atoms the nucleus.
  • Gold Foil Experiment
    • Most alpha particles went right through,  some particles were deflected
    • Discovered the atom is mostly empty space.
    • Some particles deflected and others even bounced back
    • The atom had a very dense (+) center.

Niels Bohr

  • Improved on Rutherford’s model.
  • Every atom has a specific number of electron shells.
  • Proposed that electrons move around the nucleus in specific layers, or shells.

James Chadwick

  • Chadwick discovered neutrons.
  • He called these particles neutrons.
  • He discovered particles with no charge (neutrons), also found in the nucleus.

 

The Models of the Atoms

  • Dalton’s model was just a sphere
  • Thomson’s plum pudding model was negative electrons floating in a soup of charge
  • Bohr Rutherford model is the current one

Bohr Rutherford and Lewis

  • Bohr Rutherford diagrams have the number of protons and neutrons in writing, and the electrons circling them
  • For Lewis diagrams, NEVER WRITE THE PROTON OR THE NEUTRON NUMBER, just put the valence electrons as dots or as lines

Periodic Table

  • A period is a row, it has the same number of valence shells
  • A group is a column, it has the same number valence electrons
  • The elements can be classified as metals, non-metals, or metalloids

Characteristics of Metals Metalloids, and Non-Metals

  • Metals
    • Solid at room temp. (except Mercury-Hg)
    • Lustrous
    • Malleable
    • Ductile
    • Good conductors of heat and electricity
  • Metalloids
    • Solid at room temp.
    • Can be shiny or dull
    • Not ductile
    • May conduct electricity
  • Non-metals
    • Solid liquid and gas at room temp.
    • Not lustrous
    • Solids are brittle
    • Poor or non-conductors

Properties of the groups

  • Alkali Metals
    • Highly reactive
    • Light
    • Soft
  • Alkaline Earth Metals
    • Reactive
    • Stronger than Alkali Metals
    • Denser than Alkali Metals
  • Chalogens, group 16, they exist
  • Halogens
    • Reactive
    • Dangerous
    • Oxidizers
    • Forms salts
    • Noticeable colour
  • Noble Gases
    • Very unreactive
    • Only Xenon can form compounds

 Ionic and Molecular bonds

  • Ionic bonds are like the friends you have because they are useful, you exchange info and get along well, they help you and you help them.
  • Molecular bonds are people you really like and you share everything
  • Atoms also do this, in ionic bonds, they transfer electrons and in molecular bonds they share electrons
  • Ionic bonds form because you are different (metal to non-metal) so one can exchange info
  • Molecular bonds are formed between people you are close to and you have to have something in common (non-metal to non-metal)
  • Ionic bonds have a cation (the metal) and a anion(the other one)
  • For naming, endings are mono-, di-, tri-, tetra, penta-, hexa-, hepta-,octa-,nona-,deca-

Properties of Ionic bonds

  • Solid at room temp.
  • Form crystal structures
  • Hard and brittle
  • High melting points
  • Highly soluble in water
  • Non-conductor
  • In aqueous solution- good conductor
  • Odorless

Properties of Covalent bonds (Molecular compounds)

  • Solid, liquid, or gas at room temp.
  • Forms crystal structures
  • Usually soft at room temp
  • Generally low melting points
  • Insoluble in water
  • Non-conductor
  • Strong/distinctive odor