Question from a reader: Rank the compounds NH3, CH4,PH3 in order of increasing boiling point. Explain your answer.
Question from a viewer: Water, H2O, boils at 100 degree Celsius ; ethanol, C2H5OH, boils at 78 degree Celsius, and ammonia NH3 boils at -33 degree Celsius. Rank these three compounds in order from weakest to strongest intramolecular interaction. Explain how you get your answer.
Higher boiling point = stronger intermolecular forces.
Water boils at a higher temperature because its hydrogen-oxygen bonds cause hydrogen bonding, which is a strong intermolecular force that makes the molecules stick to each other. This means you have to add more energy (heat) to get them to separate and boil.
Question from a viewer: For each of the following pairs of atoms, write a likely formula for a simple compound made from them, and indicate if the bonding is ionic or covalent.
A) Ca & Cl
B) S& H
C) Cl & N
D) Fe & Br
Ca and Cl --> Ca is a metal, Cl is a non-metal, therefore they are IONIC together
Video of me drawing the diagram to connect the two: https://www.youtube.com/watch?v=8aDXuwsDxWE
S and H are both non-metals --> they are COVALENT together.
S brings 6 valence electrons and needs two more. H brings one each, so you need TWO hydrogens to bond with ONE sulfur --> H2S
Cl and N are both non-metals --> they are COVALENT together.
N has 5 valence electrons and needs 3 more. Each Chlorine shares ONE and so you need THREE chlorines --> NCl3
Fe is a metal and Br is a non-metal --> they are IONIC together.
This one is tough unless you know (or have a periodic table that tells you) that Fe can have charges or either +2 or +3.
+2 charge --> FeBr2
+3 charge --> FeBr3
A question from a viewer: How do we find the difference between molecules and compounds? I know that all compounds are molecules, but not all molecules are compounds, but how do we find the difference by just looking at a given atom? ex: O2, O3, CO2, etc. Thank you!
A molecule is anything made of 2 or more atoms
O2 is a molecule because it is made of 2 atoms
O3 is a molecule because it is made of 3 atoms
CO2 is a molecule because it is made of 3 atoms
A compound is anything made of 2 of more ELEMENTS
O2 is NOT a compound because it is only made of oxygen
O3 is NOT a compound because it is only made of oxygen
CO2 IS a compound because it is made of carbon and oxygen (2 different elements)