What is a pure substance
A pure substance is one that is made up of just one substance. That substance can be either an element or a compound. And have a fixed melting and boiling point
What is absolute zero
-273° c
What do salt and impurities do
They lower boiling points
What is the melting point of water
0°
What is the boiling point of water
100°
What is a element
made up of only one type of atom
What is a mixture
physical combination of two or more substances (elements or compounds) that are not chemically bonded
What is a compound
a substance formed when two or more different chemical elements are chemically bonded together in a fixed ratio
How to calculate the rf value
Spot distance divided by solvent distance
How do you do the rf value practical
A pencil line is drawn on chromatography paper and the sample is placed on it.
The paper is put in a solvent with the solvent level below the line.
The solvent rises and separates the substances.
The solvent front is marked and the distances travelled by the substance and solvent are measured from the baseline.
Required Practical - Distilling Sea Water
Set up apparatus: Place the seawater into a conical flask attached to a delivery tube, leading into a test tube sitting in a beaker of ice/cold water (acting as a condenser).
Heat: Gently heat the sea water in the conical flask using a Bunsen burner until it reaches a gentle boil.
Evaporation: Water turns into steam (water vapour), leaving behind dissolved solids (salts) in the flask.
Condensation: The steam passes into the cold test tube, where it condenses back into liquid water.
Collect Product: Collect the liquid in the test tube, which is pure, distilled water.
Test Purity: Test the distilled water with Universal Indicator (should be pH 7) or test its boiling point (should boil at exactly 100°C) to confirm purity.
What is a mixture?
A mixture is a combination of two or more substances, not chemically bonded, where each substance retains its own properties and can be separated by physical methods.
What is a pure substance?
A pure substance is a single element or compound, containing only one type of particle, with a fixed composition and no other substances mixed in.
What separation technique separate an insoluble
Filtration it An insoluble solid from a liquid
Example:
• Sand + water
Sand stays as the residue, water passes through as the filtrate
What does crystallisation separate
Separates:
• A soluble solid from a solution
Example:
• Salt from saltwater
👉 Water evaporates, salt forms crystals
What does simple distillation separate
Simple Distillation
Separates:
• A solvent from a solution
Example:
• Pure water from salt solution
👉 Water evaporates and then condenses
What does fractional distillation separate
Fractional Distillation
Separates:
• Liquids with different boiling points
Example:
• Ethanol + water
• Crude oil into fractions
👉 Lower boiling point liquids evaporate first
What doe’s chromatography separate
Chromatography
Separates:
• Soluble substances with different solubilities
Example:
• Dyes in ink
👉 Substances move different distances up the paper
What does evaporation separate
Evaporation
Separates:
• A soluble solid from a solution (when you don’t need the solvent)
Example:
• Salt from seawater
👉 Water evaporates, salt remains
What does magnetism separate
Magnetism
Separates:
• Magnetic substances from non-magnetic ones
Example:
• Iron filings from sand
Why is water polar
due to an uneven distribution of electron density, creating partial negative and positive charges
