Comprehensive Study Guide: Prep 1 Science - Unit: Metals, Acids, Alkalis, and Salts

Metals and Non-Metals

• Comparison of Metals and Non-Metals based on Valence Electrons:     - Metals:         - They have less than $4$ electrons in their last energy level ($1$, $2$, or $3$ electrons).         - Example: Lithium ($Li$) is a metal because it has

• $1$ electron in its energy level (less than $4$ electrons).     - Non-Metals:         - They have more than $4$ electrons in their last energy level ($5$, $6$, or $7$ electrons).         - Example: Chlorine ($Cl$) is a non-metal because it has $7$ electrons in its last energy level.

• Physical States:     - Metals: All metals are solids, except for Mercury ($Hg$), which is the only liquid metal.     - Non-Metals: They exist as solids and gases, except for Bromine ($Br$), which is the only liquid non-metal.

• Luster:     - Metals: They possess a metallic luster (they are shiny).     - Non-Metals: They do not have metallic luster (they are opaque).

• Malleability and Ductility:     - Metals: They are ductile, malleable, and formable ($G.R.$ Iron sheets are formed by hammering because iron is a malleable metal).     - Non-Metals: They are not ductile, malleable, or formable; they are brittle ($G.R.$ Sulfur can be crumbled when hammered because it is a brittle non-metal).

• Conductivity:     - Metals: Good conductors of heat and electricity. ($G.R.$ Some electric wires are made of aluminum because it is ductile, malleable, and a good conductor of electricity).     - Non-Metals: Bad conductors of heat and electricity, except for Graphite (Carbon), which is a good conductor of electricity. ($G.R.$ Carbon is used in the manufacturing of dry columns/batteries because it is a good conductor of electricity).

• Melting Points:     - Metals: Generally have high melting points.     - Non-Metals: Generally have low melting points.

• Assessment Questions:     - How do you differentiate between Sodium and Graphite?         - In terms of metallic luster: Sodium has a metallic luster because it is a metal, while Graphite does not have metallic luster because it is a non-metal.         - Which is opaque? Graphite is opaque.     - How do you differentiate between Silver and Phosphorus?         - In terms of electric conductivity: Silver is a good conductor of electricity because it is a metal. Phosphorus is a bad conductor of electricity because it is a non-metal.

Metallic Bonding and Material Properties

• Metallic Bond Definition: It is the attraction force between positive ions and the negative electron cloud that surrounds them.

• Hardness and Valence Electrons:     - When the number of valence electrons increases, the strength of the metallic bond increases, and the hardness of the metal will increase.     - Comparison of Hardness:         - $Ca$ is harder than $Na$ because the number of valence electrons in $Ca$ is ($2$), which is greater than the number of valence electrons in $Na$ ($1$). Thus, the metallic bond in $Ca$ is stronger, leading to increased hardness.         - Hardness ranking: Aluminum ($Al$) > Magnesium ($Mg$) > Sodium ($Na$).

Recycling and Alloys

• Recycling:     - Definition: The process of converting wastes into new substances.     - Recycling of Metals: Metals like iron and aluminum are recycled.     - Benefits of Recycling ($G.R.$):         - To decrease the percentage of wastes in the earth's crust.         - Recycling is often less expensive than the cost of extracting metals from their ores.         - Difficulty of extracting pure metals from ores.

• Alloys:     - Definition: A mixture of the melts of two or more metals.     - Example: Bronze Alloy: Contains $95\%$ Copper ($Cu$) and $5\%$ Tin ($Sn$).     - Uses of Alloys: Used in making statues, jewelry, and medals.     - Scientific Details:         - Atoms of solid metals are arranged in a pattern known as a lattice.         - Alloys are not represented by a chemical formula because they are mixtures, not pure substances.     - Property Benefit ($G.R.$): Bronze alloy is used in making medals instead of pure copper because it is harder than copper and resistant to rust.

• Odd One Out Questions:     - Gold - silver - bromine - mercury: (Odd one: Bromine, as it is the only non-metal and liquid amongst metals).     - Phosphorus - Bromine - Mercury - Sulfur: (Odd one: Mercury, as it is a metal, others are non-metals).     - Iodine - Sulfur - Hydrogen - Graphite: (Odd one: Graphite, as it is a conductor).     - Bronze - Chlorine - Copper - Tin: (Odd one: Chlorine, as it is a non-metal gas, others are metal/alloys).

Atomic Groups

• Definition: An ion composed of more than one atom of more than one element that behave like a single atom.

• Common Atomic Groups:     - Monovalent (One negative charge ($-1$)):         - Hydroxide ($OH^-$)         - Nitrate ($NO_3^-$)         - Nitrite ($NO_2^-$)         - Bicarbonate ($HCO_3^-$)         - Chlorite ($ClO_2^-$)     - Divalent (Two negative charges ($-2$)):         - Carbonate ($CO_3^{2-}$)         - Sulphate ($SO_4^{2-}$)         - Sulphite ($SO_3^{2-}$)     - Trivalent (Three negative charges ($-3$)):         - Phosphate ($PO_4^{3-}$)     - One Positive Charge ($+1$):         - Ammonium ($NH_4^+$)

Acids and Alkalis

• Acids:     - Definition: A substance that, when dissolved in water, dissociates to produce Hydrogen cations ($H^+$).     - Naming Convention (Oxygen-free acids): Use the prefix "Hydro-" and suffix "-ic".         - Hydrochloric acid: $HCl$         - Hydrobromic acid: $HBr$         - Hydroiodic acid: $HI$         - Hydrosulfuric acid: $H_2S$     - Naming Convention (Oxyacids): Consist of an atomic group containing oxygen.         - Nitric acid: $HNO_3$         - Sulfuric acid: $H_2SO_4$         - Phosphoric acid: $H_3PO_4$         - Carbonic acid: $H_2CO_3$         - Nitrous acid: $HNO_2$         - Sulfurous acid: $H_2SO_3$     - Properties:         - Taste: Sour (e.g., Ketchup, Grapes).         - Effect on Litmus: Turns blue litmus paper into red. ($G.R.$ Because acids produce $H^+$ cations in water).

• Alkalis (Bases):     - Definition: A substance that, when dissolved in water, increases the concentration of Hydroxide anions ($OH^-$).     - Examples:         - Sodium hydroxide: $NaOH$         - Potassium hydroxide: $KOH$         - Magnesium hydroxide: $Mg(OH)_2$         - Calcium hydroxide: $Ca(OH)_2$         - Ammonium hydroxide: $NH_4OH$     - Properties:         - Taste: Bitter; feel: Slippery (e.g., Toothpaste, Detergents, Soda).         - Effect on Litmus: Turns red litmus paper into blue. ($G.R.$ Because alkalis produce $OH^-$ anions in water).

Conductivity and Strength of Acids/Alkalis

• Acid Conductivity:     - Strong Acids (Good conductors): Hydrochloric acid ($HCl$), Nitric acid ($HNO_3$), Sulfuric acid ($H_2SO_4$).     - Weak Acids (Bad conductors): Vinegar (Acetic acid), Nitrous acid ($HNO_2$), Sulfurous acid ($H_2SO_3$).

• Alkali Conductivity:     - Strong Alkali (Good conductors): Sodium hydroxide ($NaOH$).     - Weak Alkali (Bad conductors): Ammonium hydroxide ($NH_4OH$).

Biology and Real-world Applications

• Role in the Human Body:     - Hydrochloric acid ($HCl$): Secreted by the stomach; it is a component of gastric juice and helps in digestion.     - Lactic acid: Provides muscles with energy during a lack of oxygen. ($G.R.$ Accumulation of lactic acid causes muscle fatigue and cramps).

• Medicine:     - Milk of Magnesia: Contains Magnesium hydroxide ($Mg(OH)_2$). Used as a temporary treatment for hyperacidity to neutralize gastric acid.

• Chemical Neutralization:     - $Acid + Alkali \rightarrow Salt + Water$     - Example: $HCl + NaOH \rightarrow NaCl + H_2O$

Oxides and Acid Rain

• Basic Oxides: Metal oxides that dissolve in water to form alkalis.     - Example: Burning Magnesium forms Magnesium oxide ($MgO$). Dissolving $MgO$ in water forms Magnesium hydroxide ($Mg(OH)_2$), which turns litmus solution blue.

• Acidic Oxides: Non-metal oxides that dissolve in water to form acids.     - Example: Burning Sulfur forms Sulfur trioxide ($SO_3$). Dissolving $SO_3$ in water forms Sulfuric acid ($H_2SO_4$), which turns litmus solution red.

• Acid Rain:     - Definition: Rain resulting from the dissolution of acidic oxides in atmospheric water vapor.     - Formation: Burning fuel (petrol/coal) in cars and factories releases $NO_2$ (Nitrogen dioxide) and $SO_2$ (Sulfur dioxide). These accumulate in clouds and dissolve in vapor to form acid rain.     - Damages: Destruction of forests, harming aquatic life, corrosion of buildings, and respiratory problems.

Indicators and the pH Scale

• Chemical Indicators: Substances whose color differs in acidic and alkaline mediums.     - Litmus: Acid = Red; Alkali = Blue; Neutral = No change.     - Plant Indicators:         - Hydrangea plant: In basic soil, flowers are red/pink; in acidic soil, flowers are blue.         - Red Cabbage: Used as a natural indicator. Orange juice (acidic) turns it red; baking soda (basic) turns it green; water (neutral) results in no change.     - Safety Note: Forbidden to taste, smell, or touch chemicals in the lab because some acids are burning and some alkalis are caustic.

• The pH Scale:     - Definition: A scale between $0$ and $14$ developed by the scientist Soren Sorensen to determine acidity and basicity.     - Values:         - pH < 7: Acidic (Strength increases as pH approaches $0$).         - $pH = 7$: Neutral.         - pH > 7: Basic/Alkaline (Strength increases as pH approaches $14$).     - Measurement Devices:         - Universal indicator strips: Provide an approximate value based on color comparison.         - pH Meter: A digital device that shows an accurate value. ($G.R.$ pH meter is more accurate than universal strips).

Salts: Classification and Properties

• Formation: Ionic compounds formed by the reaction of an alkali cation and an acid anion. They can be formed via:     - Cation of metal + anion of non-metal (e.g., $NaCl$).     - Cation of metal + anion of atomic group (e.g., $NaNO_3$).     - Cation of atomic group + anion of non-metal (e.g., $NH_4Cl$).     - Cation of atomic group + anion of atomic group (e.g., $(NH_4)_2CO_3$).

• Solubility in Water:     - Soluble Salts: Sodium, Potassium, and Ammonium salts; all Nitrates; most Chlorides (except Silver chloride); most Sulphates (except Calcium sulphate).     - Insoluble Salts: Silver chloride ($AgCl$), Calcium sulphate ($CaSO_4$), and most Carbonates (except Sodium, Potassium, and Ammonium carbonate).

• The Dead Sea:     - The highest salinity in the world ($10$ times the salinity of the Red Sea).     - ($G.R.$ One cannot sink/drown in the Dead Sea because the high percentage of salts increases the water density, providing high buoyancy).