REVIEW OF SECONDARY 4 Things you should already
- Slides: 18
REVIEW OF SECONDARY 4 (Things you should already know and remember)
Why is the Periodic Table important to me? b The periodic table is the most useful tool to a chemist. b You get to use it on every test. b It organizes lots of information about all the known elements.
The Current Periodic Table The horizontal rows are called periods. b The vertical columns are called groups (families). b Group 1: Alkali Metals b Group 2: Earth Alkali Metals b Group 7 : Halogens b Group 8: Inert (Noble) Gases b Transition Metals: in the middle b
PHYSICAL CHANGES Change in state: such as boiling, melting, evaportaion, … b Basic identity of substance remains the same b b Reversible
CHEMICAL CHANGES b Basic identity of substance changes b Irreversible b Signs of chemical change: Ø Bubbles Ø Precipitate forms Ø Color change Ø Heat or light is given off Ø Electricity produced
DID YOU KNOW? b. A chemical reaction inside fireflies enables them to light up. It is called bioluminescence. b Fireflies shine for a variety of reasons. b It has been shown that females are more attracted to males who emit faster and more intensive flashes of light.
ELEMENTS b Elements are made up of only one kind of atom, and they cannot be broken down. b They are pure substances.
COMPOUNDS b They are pure substances that can be broken down into simpler substances. b They are made up of 2 or more elements that are chemically combined.
MIXTURES b They are impure substances that are combined physically and can be separated physically. b There are 2 types of mixtures: Homogeneous Heterogeneous Salt and Water Sand Water
CHEMICAL EQUATIONS Oxygen + Hydrogen Water (word equation) O 2 (g) + H 2 (g) H 2 O (l ) (chemical equation) REACTANTS PRODUCTS (g) stands for gas, (l) stands for liquid, (s) stands for solid, (aq) stands for aqueous
TYPES OF CHEMICAL REACTIONS b Synthesis: Combination Reaction Copper + Oxygen Copper Oxide Cu + O 2 Cu. O b Decomposition: Water Hydrogen + Oxygen H 2 O H 2 + O 2
Synthesis Example C + O 2 C + O O O C O CC O O O C C C OC OOC C OCO OO CO O O OO OO OOO General: A + B AB
Decomposition Example: Na. Cl Cl Na General: Cl + Na AB A + B
Single displacement Example: Zn + Cu. Cl 2 Cl Cu + Cl General: Zn Cl Zn + Cu Cl AB + C AC + B
Double displacement Example: Mg. O + Ca. S Mg O + General: Ca S Mg S + Ca O AB + CD AD + CB
More examples Single Displacement: Cu. O + C Cu + CO 2 Double Displacement: Ba. Cl 2 + K 2 CO 3 --> Ba. CO 3 + 2 KCl
Combustion Reactions b Oxygen reacts with another substance producing carbon dioxide and water and releases heat. CH 4 + 2 O 2 --> CO 2 + 2 H 2 O + heat
Balancing Chemical Equations b Balance the following Haber Process: N 2 + H 2 NH 3 b You should have got N 2 + 3 H 2 2 NH 3 b This chemical reaction is named after Fritz Haber. A German chemist who found a way to combine nitrogen and hydrogen to ammonia which can be pumped directly into the soil as a fertilizer.
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