Summary
Summary Grade 9 Chemistry (Canadian Curriculum)
- Course
- Science
- Institution
- 10th Grade
Very in-depth, well-explained set of notes that will help you thoroughly understand the basics of chemistry.
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MatterMatter: Anything that has mass and takes up space (has volume)
Pure substance: A substance that is made up of only one type of particle
- Example: Gold
Mixture: A substance that is made up of two or more different types of particles
Element: A pure substance that cannot be broken down into a simpler chemical substance by
any physical or chemical means
- An atom with a particular number of protons
- Each element has different number of protons
Compound: A pure substance composed of two or more different elements that are chemically
joined
- Example: H2O →
Mechanical mixture: A mixture where you can distinguish between different types of matter
- Not changing chemical identity
Solutions: A uniform mixture of two or more substances
- Looks “pure”
- You can’t distinguish between particles because they are so small
Classifying matter:
- Size of particle from smallest to largest: solution → colloid → suspension
*All molecules are not compounds. All compounds are molecules
Atoms & Atomic Structure
Atoms: The smallest unit of matter
- Atoms are mostly made up of empty space
Periodic table of elements: A chart of all the different types of atoms/elements organized by
shared characteristics
- Atomic number located above element
- Mass number located below element
- Number of electrons = atomic number
Atomic number: The number of protons in the nucleus
- This number determines element
- Each element has a different atomic number starting at 1 for hydrogen to above 100
- Hydrogen has one proton only (no neutrons because atomic number - atomic
mass = 1-1= 0)
- Doesn’t include electrons because they can leave and enter the atom
Atomic mass (atomic weight): Average number of protons and neutrons for all natural
isotopes
,Mass number: Total number of protons and neutrons in an atom
Yes, atomic mass and mass number are DIFFERENT and have different definitions
- BUT when it comes to drawing Bohr-Rutherford diagrams, we can assume that atomic
mass is basically the same as mass number
- However, TECHNICALLY, the number below the element is still atomic mass
Characteristics of Subatomic Particles
Protons
- Location: In nucleus
- Charge: + Positive electrical charge
- Mass: 1
- Symbol: p+
Neutrons
- Location: In nucleus
- Charge: No charge
- Which means same amount of protons and electrons
- DO NOT SAY “neutral charge”
- Mass: 1
- Symbol: n^0
Electrons
- Location: Orbiting around nucleus
- Charge: - Negative electrical charge
- Mass: 1/2000
- Symbol: e−
- In a neutral atom (most atoms), the number of electrons = the number of protons
Evolution of the Atomic model
WATCH BRAINPOP VIDEO – DO NOT NEED TO KNOW DATES OR PEOPLE
Dalton: Built atomic model called the “atomic theory of matter”
- Each type of matter is made of only one type of atom.
- Each type of atom could be put into a group called an element
- Every atom of a given element was identical.
- For example, gold atoms make gold, iron atoms make iron, and so on.
- Atoms could not be created, divided into smaller parts, or destroyed
Thomson: Discovered the electron
- Thompson used a vacuum tube with metal plates at both ends and an electrical source
for his experiment.
- He found that a beam would form between the two plates; the cathode and the anode.
- Putting a magnet near the beam caused it to bend, which meant that the particles of the
beam were electrically charged.
- The cathode rays were made of negatively charged particles, later called electrons.
, - Because matter is mostly neutral, atoms must contain both positive and negative
charges that cancel each other out.
- Negatively charged electrons must be stuck all throughout a positively-charged area.
Rutherford: Discovered nucleus and protons
- Beamed positively charged alpha particles at a sheet of really thin gold foil.
- So many particles could pass right through the thin gold foil, so thought that gold atoms
must be mostly empty space.
- But some of the particles bounced off, so revised to say that a gold atom must have
some very small, positively charged mass.
- He named this mass the nucleus.
- He called the positively charged nucleus particles protons, and said that the electrons
were scattered in empty space around the nucleus.
Chadwick: Discovered neutrons
- New particles in the nucleus that weren’t affected by an electric field at all
- Alpha particles in the experiment had knocked them loose
- Chadwick called these uncharged particles neutrons.
Bohr: Discovered energy levels
- Electrons are arranged in energy levels.
- The lower energy levels are closer to the nucleus and can hold just a few electrons.
- The higher energy levels are farther away and can hold more electrons.
Since then, scientists have refined the so-called Bohr model. Electrons have levels, but they
don't orbit the nucleus in neat little circles. Instead, they exist in a region called the electron
cloud.
Dalton: Billiard Ball Model
- All matter is made up of tiny visible particles called atoms
- All atoms of an element are identical
- Atoms of different elements are different
- (Atoms rearranged but never created/destroyed to form new substances)
J.J. Thompson: “Plum Pudding” Model
- Atoms contain negatively charged electrons
- Since atoms are neutral, the rest of the atom is a positively charged sphere
- Negatively charged electrons are evenly distributed throughout atom
- His claims later proven NOT CORRECT → So do not take in/apply this information
Rutherford: Gold foil experiment
- Centre of an atom has a positive charge called nucleus
- Contains most of atom’s mass yet very small space
- Nucleus is surrounded by a cloud of negatively charged atoms – electrons
- Most of atom is empty space
Chadwick
- Nucleus contains positively charged protons and neutral particles called neutrons
- Mass of a neutron is about the same as a proton
- Neutral atom has the same amount of protons and electrons
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