Results for "Melting Point"

Key definitions - Atomic structure and the Periodic Table

METHOD FOR DETERMINING THE MELTING POINT OF A SAMPLE

STRUCTURAL EFFECTS ON SOLUBILITY, MELTING POINT, AND BOILING POINT

Laboratory Operations- Melting point determination and rotary evaporation

**Properties of Matter** - **Physical vs Chemical Properties** - *Physical Properties:* Can be observed without changing the substance (e.g., color, density, melting point, boiling point) - *Chemical Properties:* Describe a substance’s ability to undergo chemical changes (e.g., flammability, reactivity with acid) - **Examples of Each** - Physical: Ice melting, water boiling, density, solubility - Chemical: Rusting iron, burning wood, tarnishing silver - **Intensive vs Extensive Properties** - *Intensive:* Do not depend on the amount of matter (e.g., density, boiling point, color) - *Extensive:* Depend on the amount of matter (e.g., mass, volume, length) --- **Density** - **Definition, Units, and Formula** - Density (ρ) = Mass (m) / Volume (V) - Units: g/cm³ (solids), g/mL (liquids), kg/m³ (gases) - **Comparison of Densities** - Solids: Generally highest density - Liquids: Lower density than solids but higher than gases - Gases: Lowest density - **Solid: Regular vs Irregular Shape** - *Regular Shape:* Use geometric formulas to find volume - *Irregular Shape:* Use water displacement method - **Factors Affecting Density** - Temperature (increase decreases density for most substances) - Pressure (affects gases significantly) - Composition (different materials have different densities) --- **Elements, Compounds, and Mixtures** - **Matter: Definition and Examples** - Anything that has mass and takes up space (e.g., air, water, rocks) - **Pure vs Impure Matter** - *Pure:* Elements and compounds (e.g., oxygen, water) - *Impure:* Mixtures (e.g., saltwater, air) - **Atom vs Element** - *Atom:* Smallest unit of an element - *Element:* Substance made of one type of atom - **Compounds vs Mixtures** - *Compounds:* Chemically bonded elements (e.g., H2O, CO2) - *Mixtures:* Physically combined substances (e.g., salad, air) - **Types of Mixtures** - Homogeneous (solutions, uniform throughout) - Heterogeneous (distinct parts, not uniform) - **Examples of Mixtures** - Homogeneous: Saltwater, air - Heterogeneous: Salad, granite --- **Solubility** - **Solutions** - *Parts:* Solute (dissolved substance) + Solvent (dissolving substance) - *Examples:* Saltwater (solute: salt, solvent: water) - **Effect of Temperature and Pressure** - Higher temperature increases solubility of solids in liquids - Higher pressure increases solubility of gases in liquids - **Gases vs Liquids** - Gases dissolve better in cold liquids under high pressure - Liquids dissolve better at higher temperatures - **Gaseous, Liquid, and Solid Solutions** - Gaseous: Air (oxygen in nitrogen) - Liquid: Saltwater (NaCl in H2O) - Solid: Alloys (brass, steel) - **Concentrations** - Unsaturated: Can dissolve more solute - Saturated: Maximum solute dissolved - Supersaturated: Holds more than normally possible - **Solubility Curve** - Shows solubility vs temperature - Higher points indicate higher solubility --- **The Mole** - **Avogadro’s Number** - 6.022 x 10^23 particles per mole - **Molar Mass** - Mass of one mole of a substance (g/mol) - **Particle, Mass, and Mole Calculations** - Particle calculations: Using Avogadro’s number - Mass calculations: Converting between grams and moles - Mole calculations: Determining amount of substance - **Moles at STP (Standard Temperature and Pressure)** - 1 mole of gas = 22.4 L at STP - **Atomic Mass Units (AMU)** - Unit for atomic/molecular mass --- **Labs** - **Density Lab** - Measure mass and volume, calculate density - Compare densities of different materials - **Elements, Compounds, and Mixtures Lab** - Classify substances based on their properties - **Mystery Powder Lab** - Identify unknown substances using solubility and reactions - **Cornstarch Lab** - Explore properties of non-Newtonian fluids This guide covers essential concepts in matter, density, solubility, and the mole, along with relevant lab activities

Lab 3: Melting Points and Recrystallization

Chapter 2: Intermolecular Forces and Application on Boiling Point and Melting Point

Ch 2 Chemical Compounds and Bondings Chemical bond: force of attraction between 2 atoms or 2 ions. There are 2 main types of chemical bonds: 1. Ionic bond: a bond between a metallic atom (metal) and a non-metallic atom (non-metal) in which there is a complete transfer of electrons from the metal to the non-metal. The compound which is formed is called an ionic compound. Ex.: NaCl , MgCl2, Al2O3 To write the formula of an ionic compound we use the criss-cross method (we down cross multiply the charges without the sign, only the numbers of the charges) Remark: if the charges are the same then they cancel each other in the formula so there will be one atom of the metal and one atom of the non-metal in the compound. Exercise: Write the formula of the compound which is formed between the following elements, and name each compound. a) Rb and S: b) Ca and Se: c) Al and Br: d) Na and N: - Draw a Bohr diagram to show the transfer of electrons (loss / gain) in an ionic compound. Example: Na2O (sodium oxide) Remark: The ionic bond is also described as an electrostatic force of attraction between a positive ion and a negative ion (eg: Na+ Cl- ). 2. Covalent bond: a bond between a non-metal and another non-metal in which there is a sharing of electrons between the non-metallic atoms. The compound that is formed is called a covalent or molecular compound. Molecule: 2 or more atoms (non-metallic) bonded together; the atoms can be of the same element such as O2 or of different elements such as HCl, CH4, H2O,….. We show the sharing of electrons between non-metallic atoms by using the Lewis diagram. In addition we can make intersecting circles for the atoms to show the sharing. Reminder: Lewis diagram of an atom shows only the valence electrons of that atom. Most of the atoms follow the octet rule (there are very few exceptions), that is each atom will have eight electrons in the valence shell (same as noble gases) except hydrogen will have 2 electrons after sharing (same as helium). Remark: 2 electrons that are not bonded to any other atom is called a lone pair (non-bonding pair) of electrons. Exercise: Draw lewis diagrams to show the sharing of electrons in each of the following compounds: 1. NF3 2. CH4 3. CO2 4. CCl4 5. CH2O Remark:In drawing Lewis structure, we show the bonds between the atoms and we also show all lone pairs (if present) on any atom. - Naming molecular compounds: 1: mono 2: di 3: tri 4: tetra 5: penta 6: hexa 7: hepta 8: octa 9: nona 10:deca Example: PCl5 : phosphorus pentachloride Remark: If the first element contains only one atom we don’t write mono before it; If the second element contains only one atom we have to write mono before it. Ex.: NO : nitrogen monoxide CO: carbon monoxide Exercise: Fill in the table below Name Chemical Formula diphosphorus pentoxide SO3 CO Aluminum sulfide Al2S3 SF6 Calcium oxide Lithium nitride Li3N Remark: If the compound contains a transition metal, then we have to mention the type of charge of the transition metal by inserting a roman numeral in brackets (I, II, III, IV ….) after the symbol of the transition metal. Example: Name the following compounds: - FeCl2 : Iron (II) chloride - Cu(NO3)2 : Copper (II) nitrate Remark: There are few transition metals that have only one type of charge such as zinc, nickel, and silver; in this case no roman numeral is required. Zinc : Zn+2 Silver: Ag+ Nickel: Ni+2 - ZnSO4 : zinc sulfate - AgNO3 : silver nitrate - CuSO4 : copper (II) sulfate - Co(NO3)3 : cobalt (III) nitrate Exercise: Write the formula of the following compounds. Calcium phosphate: Iron(III) hydroxide: Sodium hydroxide: Manganese(II) hydroxide: Barium sulfate: Zinc carbonate: Ammonium nitrate: Remark: We must enclose the polyatomic ion in brackets if the number after it is more than 1. Note: If the polyatomic ion that ends with the prefix –ate decreases by one oxygen atom then the prefix changes to -ite. If the prefix ending with – ite decreases by one oxygen atom then we precede the prefix by hypo, whereas if the prefix ending with – ate increases by one oxygen atom then we precede the prefix by per. Example: ClO3- is called chlorate; if we reduce one oxygen atom then the ion becomes ClO2- and is called chlorite, however if we increase by one oxygen atom then the ion becomes ClO4- and is called perchlorate; and if the chlorite is reduced by one oxygen atom then the ion becomes ClO- and is called hypochlorite. Exercise: Name the following compounds: K2SO3 : NaNO2 : Mg(ClO4)2 : LiBrO2 : - Comparison Table between ionic and covalent (molecular) compounds: property Ionic Compounds Covalent Compounds State (at room temperature) solids Solids, liquids or gases Melting point and boiling point Very high Usually low Involvement of electrons Loss and gain (transfer) of electrons Sharing of electrons Electric conductivity When dissolved in water (in solution) , electric conductivity is high

3.10 Describe the bonding in diamond and graphite in terms of the hybrid orbital model (valence bond theory). Explain how the macroscopic properties of diamond and graphite (appearance, melting point, strength, electricity conductance, etc.) can be explained in terms of the kind of bonding that occurs in these networks.

3.6 Predict, draw models (pictures), and explain why relative melting points and boiling points for substances that exist as molecules (like H2) differ from those that exist as continuous extended networks (like diamond or metals).

3.5 Differentiate between properties of atoms, nano-particles, and larger macroscale materials. Explain why is it that atoms don’t have macroscopic properties like melting point, boiling point, and color, while macroscopic materials do (and can be identified by them)

Exercise 3: Boiling Point and Melting Point of Organic Compounds (copy)

POC LAB - Boiling and Melting Point

Exercise 3: Boiling Point and Melting Point of Organic Compounds

ORG CHEM LAB - STRUCTURAL EFFECTS ON MELTING POINT AND BOILING POINT

EXP 6: Micro-Determination of Boiling Point & Melting Point

Lab 1: Melting Point and Recrystallization

Experiment 9 Melting point and boiling point

Chem Chapter 19 Final - Chapter 19: Lipid terminology, melting points of fatty acids, phospholipid properties

Melting Point and Acid-Base Indicator