Chemistry Grade 9
SNC 1W1 Exam Review Chemistry For The Grade 9’s:
1. Compound: “A cake” – It’s made of different ingredients (elements) stuck together.
2. Mixture: “Trail mix” – Everything’s in the same bowl, but not stuck together.
3. Molecule: “A pair of shoes” – Two or more atoms tied together (like laces).
4. Diatomic Molecule: “Best friends” – Always go together in pairs (like O₂ or N₂).
5. Pure Substance: “Distilled water” – Just one thing, no extras added.
6. Element: “A Lego brick” – The simplest piece that builds everything.
7. Family: “A sports team” – They’re in the same group and play the same “game” (react similarly).
8. Period: “A row of seats” – Everyone’s sitting in a line (horizontal row).
9. Metal: “A shiny sword” – Strong, shiny, and conducts electricity.
10. Non-Metal: “A balloon” – Not shiny, doesn’t conduct, and sometimes floats around (like oxygen).
11. Heterogeneous Mixture: “A fruit salad” – You can see all the different parts.
12. Homogeneous Mixture: “Hot chocolate” – Looks the same all the way through.
13. Density: “Packing a suitcase” – The more tightly you pack it, the denser it is.
14. Standard Atomic Notation: “An ID card” – Shows an atom’s important details.
15. Ionic Bond: “Giving away candy” – One atom gives another an electron to make them both happy.
16. Covalent Bond: “Sharing a pizza” – Atoms share electrons to stick together.
17. Molecular Formula: “A grocery list” – Tells you what and how much is in a molecule (like H₂O = 2 hydrogens, 1 oxygen).
18. Chemical Property: “How spicy food is” – It only changes when you eat it (reacts).
19. Physical Property: “How soft a pillow is” – You can feel or see it without changing what it is.
Here are oversimplified answers for a Grade 9 level:
1. What is the particle theory of matter?
Is made up of tiny particles that are always moving, have space between them, and are attracted to each other
3. What are the families of the periodic table?
Vertical columns (up —> down) in the periodic table.
What do elements within a family have in common?
They have the same number of valence electrons and similar properties
• How does reactivity change when moving up or down a column?
Metals (like Alkali Metals) are more reactive the further you go down
Non-metals (like Halogens) are less reactant the further you go down
• Which families are more reactive?
• Alkali Metals (most reactive metals).
• Halogens (most reactive non-metals).
3. What is an isotope?
Atoms of the same element with the same number of protons but a different number of neutrons.
4. What does it mean to have a stable octet?
It means an atom has 8 electrons in its outer shell, making it stable (like noble gases).
5. Draw Bohr-Rutherford (B-R) and Lewis-Dot (L-D) diagrams.
• B-R Diagram: Shows all electrons orbiting around the nucleus.
• L-D Diagram: Shows only valence electrons as dots around the element symbol.
• B-R Ions: Add or remove electrons in the outer shell to show charges (e.g., Na⁺ loses one electron).
6. Use B-R or L-D diagrams to show how atoms form ionic bonds.
• Draw B-R or L-D diagrams to show one atom transferring electrons to another.
• Example: Sodium (Na) gives 1 electron to Chlorine (Cl), forming Na⁺ and Cl⁻.
• Flow Chart: Transfer → Ions → Bond forms due to opposite charges.
7. How are pure substances, mixtures, elements, and compounds related?
• Pure substances: Have a fixed composition (e.g., water).
• Mixtures: Two or more substances combined (e.g., air).
• Elements: Only one type of atom (e.g., oxygen).
• Compounds: Two or more types of atoms chemically combined (e.g., CO₂).
8. Determine the number of valence electrons in a neutral atom.
Check the element’s group number:
• Group 1 → 1 valence electron
• Group 17 → 7 valence electrons
9. Determine the number of bonds an atom will make.
Atoms form as many bonds as needed to get 8 valence electrons.
• Example: Oxygen (6 valence electrons) forms 2 bonds.
10. Determine the formula of a compound.
• Use the crisscross method: Swap charges of ions.
• Example: Magnesium (Mg²⁺) + Chlorine (Cl⁻) → MgCl₂.
11. Be familiar with the names and symbols for the first 20 elements.
Examples:
• Hydrogen (H), Helium (He), Carbon (C), Oxygen (O), Sodium (Na), Calcium (Ca).
12. Know how to name ionic compounds.
• Write the metal first, then the non-metal with “ide.”
• Example: NaCl → Sodium Chloride.
13. Determine the number of atoms of each element in a molecule based on the molecular formula.
• Count the subscript numbers:
• Example: H₂O → 2 Hydrogen, 1 Oxygen.
• CO₂ → 1 Carbon, 2 Oxygen.