chem

Matter

Physical Changes

A physical change is one which the chemical composition goes unchanged.

For example, when an ice melts, it melts back into its physical form of a liquid.

The way the water molecule is arranged, changes, but are still water molecules.

Chemical Changes

A chemical change refers to when the composition of the chemical reacts to a certain change, therefore changing the form of the chemical.

when the hydrogen molecule bonds with oxygen, it creates water molecule,

notice that Hydrogen and Oxygen used to be connected to themselves but have now joined to make a water molecule.

Elements

Elements are pure substances which can`t be divided into anymore form or another substance by any physical process.

That is why water is a molecule; a molecule is a chemical bond of other atoms; an atom can`t be broken down by any physical or chemical means.

Let`s take water again, water is not an element, it is a compound of Hydrogen and Oxygen and can be split into elements

Mixtures

Mixtures are made up of two or more pure substances. These can be separated by physical processes. For example, when you heat up saltwater, you are simply evaporating the mixture, therefore it will allow the salt and the water to separate, leaving only the salt behind. In contrast, a compound like water requires a chemical reaction to separate its constituent elements, highlighting the fundamental differences between mixtures and compounds.

There can be 2 types of solutions,

A Homogeneous Solution - which refers to when every aspect of the solution looks the same, and is distributed evenly

A Heterogeneous Solution - which means that the substance is not distributed properly, meaning they would also appear differently

Properties of Water

Water, as we know, is the most essential compound on earth in order to survive.

And as universally accepted, it is the most commonly used solvent. But what makes water such a good solvent?

water molecules are made up of 2 hydrogen atoms, and one oxygen atom (H20)

Water molecule forms through covalent bonding, where two hydrogen atoms, each with a positive partial charge, share electrons with a slightly negatively charged oxygen atom.

This sharing of electrons creates a strong covalent bond, holding the atoms together to form H₂O.

Notice the V-shape of the molecule which helps the molecules to stick together with negative and partially positive charges.

So much so that they stick together, creating Hydrogen Bonds.

Hydrogen Bonds

Essentially what happens is that the positive pole around the hydrogen atom

bonds to the negative pole around the oxygen atom around a DIFFERENT molecule

one property that is a result of these hydrogen bonds is high cohesion for water which results in high surface tension

cohesion - Cohesion is the attraction between two-like things, like the attraction between two molecules of water.

Water has the highest cohesion in any non-metallic liquid, this can be observed if tested on objects like wax paper or a leaf, where water beads up

This occurs due to because water adheres strongly to itself and weaker to the leaf, creating the east amount of surface area, with higher surface tension.

But there are other substances which are unaffected by the cohesive property of water because more adhesive.

Take glass for instance, notice the water is spreading out here, instead of beading up, due to adhesion, instead of cohesion.

the Adhesive forces of water and the glass are stronger than the cohesive forces of the individual forces of the water molecules.