Prelim Chemistry Module 1

What is a Hypothesis?

A testable statement or prediction about the relationship between two or more variables, formulated based on observations.

What are qualitative variables?

Variables that describe qualities or characteristics, often expressed in non-numerical terms.

What are quantitative variables?

Variables that represent measurable quantities, typically expressed in numerical terms.

What makes an experiment valid?

An experiment is valid if it tests the intended hypothesis and addresses its purposes.

What makes an experiment reliable?

The capacity for an experiment to be recreated and produce consistent results.

What makes a result of a measured value accurate?

The degree to which a measured value reflects the true value of the quantity being measured.

What makes the result of a measured value precise?

The degree to which measured values across multiple, identical tests produce the same or very similar results.

What type of error is a mistake?

A human error that occurs as a result of misreading, miscalculating or recording data incorrectly.

What constitutes a systematic error?

A systematic error is an error which occurs or would occur consistently or repeatedly, often as a result of incorrectly calibrated equipment, faulty equipment or flawed procedures.

What is a random error?

A random error is a type of error which occurs as a result of unforeseen or extraneous variables, causing measurements to vary, often minimally.

What is an aqueous (aq) substance?

A solution in which a solute is suspended in water (the solvent). This is because water is an excellent solvent enabling particles of dissolved substances to move freely. This makes reactions with other aqueous substances easier.

Element

A singular type of atom

Compound

A material made out of multiple types of atoms in fixed ratios.

What does an increase in temperature mean for particles?

Particles at higher temperature have more kinetic energy, causing them to move more, causing higher collision rates and rate of diffusion. Depending on the substance, energy increase can be substantial enough for particles to push far enough from each other to change states.

Fluids

Gases and Liquids are both referred to as “Fluids” as they have no fixed shape (fluidity).

When is Filtration used?

Filtration is used to separate mixtures in which one component is a solid and another is a liquid.

When is vaporization (evaporation) used?

Vaporization or evaporation used when separating a liquid from a dissolved solid and the liquid has a lower boiling point. In this, the liquid is evaporated/vaporized and the solid residue remains.

When is distillation used?

Distillation is used to separate mixtures of multiple liquids where the boiling points of the components are substantially different (over 25 degrees Celcius).

When is fractional distillation used?

Fractional distillation is a form of distillation utilising a fractionating column to separate substances with slightly differing boiling points

When is using a solvent to separate mixtures used?

If one substance in a mixture is soluble, a solvent can be added to dissolve it, allowing for the new mixture to be filtered, separating liquid from solid. This new mixture can then be separated.

When is magnetic separation used?

Magnetic separation is used to separate components with magnetic properties from mixtures. e.g. Iron filings from sand.

Solution

A homogeneous mixture of a solvent and solute in which the particles of a solute are dissolved into a solvent but do not form a new substance.

Suspension

A heterogeneous mixture in which large solid particles do not dissolve into a liquid solution and settle.

Colloid

A heterogeneous mixture in which mid-sized particles do not settle. Insoluble particles suspended throughout another substance. Colloids scatter light and are often opaque.

Heterogeneous Mixture

Heterogeneous mixtures are those which do not have uniform composition. (Hetero meaning other/different) These can consist of suspensions and colloids in which particles are large and medium sized respectively.

Homogeneous Mixture

Homogeneous mixtures are those which have uniform composition. (Homo meaning same) Solutions are homogeneous, in which solute particles are small and are uniformly dissolved into a solvent.

Dispersed Phase

The “solute” or particulate in a colloid. These can be any state of matter and can have a medium of any state of matter, they do not have to be the same.

Dispersion Medium

The “solvent” or particulate medium in a colloid.

Immiscible

(of) not forming a homogenous substance when combined.

Emulsion

A type of colloid in which two immiscible substances are forcible mixed, where one breaks into colloidal droplets which dispersed throughout the other. e.g. oil spills.

Emulsifying agent

a substance which prohibits the coalescence of dispersed liquids in an emulsion.

Gravimetric Analysis

Quantitative determination of the components of a mass as part of the whole. (Percentage of total)

Percentage composition of total mass formulau

(Mass of Substance / Total Mass of the sample) * 100

Metals on the Periodic Table

Share common traits including lustre, malleability, ductility, conductivity, high density and high boiling and melting points.

Periodic table organisation

Elements are organised by similarity. For example, metalloids are located together and have similar traits. This is the same for metals. Non-metals possess a wide range of traits but are also grouped together aside for hydrogen.

What is a lone pair?

“Lone pairs” refers to a pair of non-bonding electrons in a molecule. These take up slightly more space than bonded electron pairs, influencing the shape of a molecule.

What is the difference between dispersed force and dipole-dipole force?

Dipole-dipole intermolecular bonding is between polar covalent molecules wherein the positive charge of one molecule is attracted to the negative charge of another. In contrast, dispersed force is the intermolecular bonding of non-polar particles wherein the constant movement of electrons creates “instantaneous dipoles” that cause non-polar particles to be attracted to each other.

What does a double or triple covalent bond refer to?

The number of shared electrons shared in a bond is referred to as “single” if it is only 1, “double” if it is two, and “triple if it is three”.

Metal Bonds

Metal Cations in a regular arrangement are surrounded by a sea of unattached valence electrons.

Metal Properties Cause

Lustre is caused by the electron’s absorption and expulsion of light waves.
Malleability and Ductility are a result of the cation’s ability to shift within the “sea” of electrons.
Electric conduction is a result of electric charges ability to travel easily through the “sea of electrons”

Why do some metals have higher melting points than others?

Certain metals have greater bond strength between the electrons and metal cations as a result of certain ionic charges. E.g. Magnesium is 2+ and thus has a greater attraction to electrons than Sodium which is 1+