Chemistry Unit 2: Mixtures and Solutions

For the Grade 7 Science curriculum of the IB utilising the Cambridge grade 8 textbook.

Mixture

blend of two or more substances when each of them has its own identification and properties.

Mixture states of matter

soild, liquid or gas

Two types of mixtures

Homogeneous and Heterogeneous

Homogeneous

uniform composition of atoms or molecules

heterogeneous

non-uniform composition throughout the mixture.

Homogeneous naked eye

individual liquids cannot be seen by the naked eye.

Heterogeneous naked eye

individual liquids can be seen through the naked eye

Homogeneous atom distribution

evenly distributed throughout the solution

Heterogeneous atom organisation

non-uniform in the solution

Homogeneous phases

They have single phases.

Heterogeneous phases

They have two or more phases.

Homogeneous separation

mixture isn’t physically separable.

Heterogeneous separation

can be easily separated.

Phase

Alternative method of mentioning the states of matter.

Homogeneous constitution

smaller particles constitute the mixture

Heterogeneous constitution

Larger particles constitute the mixture

Homogeneous physical properties

individual components have same physical properties

Heterogeneous physical properties

Individual components have different physical properties

Homogeneous stability

They are more stable

Heterogeneous stability

They are less stable

Stability

Reactive, ability to cause chemical reactions with other substances

Homogeneous solvation

More solvation capacity

Heterogeneous solvation

less solvation capacity

Solvation

Where Solvent molecules surround and interact with solute ions or molecules.

Solvent

Liquid in which something is dissolved

Solute

what is dissolved in a solution

Homogeneous mixture example

Solution is an example for this mixture.

Heterogeneous mixture example

Suspension is an example for this mixture.

Suspension

Solid particles spread throughout the liquid without dissolving it

Homos

Greek word for ‘same’.

Hetero

Greek wrod for ‘different’.

Homogeneous mixture separation

separated through the processes of evaporation, chromatography, and distillation.

Mixtures and Compounds

They can also contain compounds. For example, air’s a mixture of various elements and compounds (excretion from energy sources, etc.)

Mixture similarities to addends

each element or compound has its usual properties.

Purity

only containing a single substance.

Example of Purity

Pure water’s just water, with no substances mixed with it.

impurity

Mixtures are made of different particles mixed together, and is the antithesis to purity.

Alloys

Metal mixtures made through mixing different metals together and melting them.

Bronze

alloy between copper and tin

Steel

mixture between iron and carbon, sometimes mixed with chromium and nickel.

Bronze hardness

Bronze is harder than either copper or tin.

Solution example

Mineral waters are one kind of this type of mixture.

Separating food dye and water

separated utilising a piece of apparatus designated as the condenser.

Condenser

apparatus utilised for separating mixtures of two liquids.

Separating mixtures utilising properties

properties of different substances inside a mixture can be utilised for the separation of them.

Function of Chromatography

technique that separates colour mixtures (such as black ink)

Chromatography paper

Special paper, like filter paper or blotting paper is used.

Chromatography

technique where an interaction with water physically with special paper properties containing ink can split the ink into many different colours.

Chromatogram

The resultant of the interaction with water utilising chromatography.

Difference in ink dissolution

some inks don’t dissolve in water.

Difference in ink dissolution example

inks in permanent marker pens can’t be dissolved in water.

Different liquids resulting in different results for Chromatography

alcohol can be utilised to dissolve inks of permanent marker pens.

Chromatography study

utilised to study the dyes used in food.

variability in food dye mixtures

Some are pure, while others are mixtures.

Uses of Chromatography

it has a wide range of uses

Common properties of solutions

they’re all transparent, which means that you can see through them.

Conservation of Mass

concept where the mixture of the solute and solvent doesn’t result in the loss of mass between them.

Solute appearance

it does not disappear when a solution is formed. The particles are so small that it can’t be observed with the naked eye.

Concentration

when a mixture has more particles of the solute dissolved in it

Dilute

When a mixture has less particles of the solute dissolved in it

insoluble

solid that won’t dissolve in water

insoluble substance example

iron fillings

saturated solution

The end point where no more solid will dissolve beyond that point.

Variability in solubility

sodium chloride has a better solubility than lead chloride

comparing solubility

measuring how much of each solutes will dissolve in 100g of the solvent.

temperature and solubility

most solutes will dissolve more quickly and easily in the vicinity of a hot water than a cold water, which means that a greater amount of mass can be dissolved than in cold water.

Different solvents

water isn’t the only solvent

Difference between solvents

some substances that are insoluble utilising water will dissolve when utilising other solvents

Variables

Different things that could affect the results.

Independent variable axis

horizontal (x) axis

dependent variable axis

vertical (y) axis

pigment

dye

ionic substance

made up of a metal and a nonmetal with opposite net charges for each respective substances.

Supersaturation

A solution (with more solute than the saturated solution) that contains more undissolved solute than the saturated solution because of its tendency to crystallize and precipitate.

Emulsion

a form of colloid that forms when you mix two liquids that normally don’t mix, through an emulsifying agent.

colloid

any substance consisting of particles substantially larger than atoms or ordinary molecules but too small to be visible in the unaided eye.

Stationary Phase

Phase in which paper chromatography is very uniform, absorbent paper

Mobile Phase

Solvent that moves through the paper, carrying different substances with it

Variability in attraction of substances

The different dissolved substances in a mixture are attracted to the two phases in different proportions. This causes them to move at different rates through the paper.

Chromatogram distinguishing

it is used to distinguish between pure and impure substances

Pure substance in Chromatogram

Produces only one spot on the Chromatogram

Impure substance in Chromatogram

Produces two or more spots on the chromatogram

Finding substances with chromatogram

This paper result can also be used to identify substances by comparing them with known substances.

Chromatogram same substance signifier

They produce the same number of spots, and these match in colour

Chromatogram same substance signifier

the spots travel the same distance up the paper (have the same R, value)

Rf

Used to identify unknown chemicals if they can be compared to a range of reference substances.

Rf value similarity

it is always the same for a particular substance out of the many reference substances.

Rf value calculation

Distance travelled by substance, and the distance travelled by solvent

Rf values variation

It varies from 0 to 1

Rf value 0

The substance is not attracted at all to the mobile phase

Rf value 1

The substance is not attracted at all to the stationary phase

Solvent front

line indicating the furthest distance a developing solvent travelled

Baseline

The portion of the chromatogram recording the detector response when only the mobile phase emerges from the column. Starting point for ink

Supersaturation and temperature

These levels of concentration requires a heating of the solvent and a bulk of the solute dissolved within it.

suspension particles

they are larger than their homogeneous counterparts (solute)

Solubility Curves

utilised to visualise the temperature dependency of the solubility of a substance.

Pressure effect on solubility

it has little effect on solids and liquids, but significant effects on gases.

Chemical Change

a change in a substance that alters the chemical composition of the substance. (the change in bonds, etc.)

Physical Change

a change in a substance that doesn’t alter the chemical composition of the substance.

Precipitation

rapid formation of a solid phase (crystals) under high supersaturation conditions, generally without nucleation.