Grade 10 Science Exam Notes

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Grade 10 Science Exam Study Note
Chemistry – Pg1, Biology – Pg11, Optics/Light – Pg 20

Chemistry
Physical and chemical properties and changes
Physical Properties: Something you can see or observe with your senses oState
oColour
oSize
oLuster/Shinyness
oSmell
oMelting/Boiling Points
oSolubility
oViscosity
oDensity
Chemical Properties: Characteristics used in a chemical reaction oTendency to React
oCombustibility
oTendency to Rust
Physical Changes
oEasily reversible
oDoesn’t change the substance
oOnly changes physical properties
Chemical Changes
oCreates new substance
oUsually irreversible
oCan change physical properties in addition to changing chemical ones Evidence of chemical changes:
Change in colour
Heat or light produced
Production of gas bubbles
Precipitate formed
Change in smell
Patterns and the Periodic Table
oPeriods: The rows of the table that refer to the number of orbits oGroups: The columns of the table that indicate the number of valence electrons 1st Group Alkaline Metals: Very reactive due to having only 1 valence electron (Lithium, Potassium) 2nd Group Alkali Earth Metals: Quite reactive due to only having 2 valence electrons (Calcium, Magnesium) 3-6 Group Metalloids: Semi reactive, have traits of both metals and non metals (silicon, boron) 4-6 Group Other Non-Metals: Broad characteristics, can create molecular compounds (Oxygen, nitrogen, carbon) 7th Group Halogens: Very reactive due to having only 1 less than a full shell (Flourine, Chlorine) 8th Group Noble Gases: Not reactive due to having a full shell (Argon, Neon, Helium) oCations are Positive Ions

oAnions are Negative Ions
Lewis dot diagrams
Electron arrangements and reactivity. Explain why alkali metals are highly reactive. oElectrons are arranged into shells as are shown in the Bohr-Rutherford diagrams right. Lithium (Li-7) has only one electron in it’s outermost shell (one valence electron) which makes it very prone to reactions because it only needs to lose one electron to become stable and have a full outer shell. Similar is Fluorine (F-19) which only needs to gain one to become stable. Both Alkali Metals (group that Lithium is in) and Halogens (group that Fluorine is in) are highly reactive due to their having only 1 valence electron, or 1 less than a full outer shell respectively.

Ionic compounds and their properties
oPropetieis: Always have one metal and one non-metal. The metal is said first and then the non-metal with –ide on the end. They also have very strong bonds and many are electrolytes which mean when dissolved in water, they conduct electricity. Pure water is a bad conductor of electricity but tap water, lake water, ocean water, and pool water are very good conductors because they contain many dissolved ions. Therefore it is very important to stay out of the water during lightning storms. oE.x. NaCl Sodium Chloride. (Table Salt)

oNaming ionic compounds
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oWriting chemical formulas of ionic compounds
When writing chemical formulas for ionic compounds remember that the charge of the new compound must be zero. Therefore an easy way to ensure this is to use the “crisscross” method as is seen below. Just remember to reduce to smallest terms if possible. (i.e. 2,2 -> 1,1) oElements with multiple ionic charge:

Some Metals have multiple charge possibilities and therefore must be specified when writing them in an equation or in any form. o
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o
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oPolyatomic ions: These are ionic compounds that instead of a single non-metal as the second ion, have a polyatomic ion. Remember that polyatomics are one unit and can’t be separated in reactions.

Molecules and Covalent Bonding
oCovalent bond, molecules and diatomic molecules
Covalent Bond: A bond that results from the sharing of outer electrons between non-metals atoms Molecule: A particle in which atoms are joined by covalent bonds Diatomic Molecule: A...
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