Chemistry: Principles of Chemistry

kinetic theory of matter

states that matter is made up of particles moving in constant, random, motion.

Kinetic theory is proved by

osmosis, diffusion, brownian motion

Diffusion

The movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached

Osmosis

The movement of water particles from a higher concentration to a lower concentration through a selectively permeable membrane

brownian’s motion

Created by robert brown, studied the movement of pollen grains on water, noticed they collided with air and water molecules and moved in constant random motions

States of matter

Solid, liquid, gas

Properties of solods

fixed shape, fixed volume, cannot be compressed, great intermolecular force between particles, thus causing limited movement of particles (they just vibrate in place)

Properties of liquids

• take the shape of the container

• Fixed volume

• Slightly compressable

• Moderate intermolecular forces of attraction

• Particles slide over each other

Properties of gases

• take the shape of the container

• Take the volume of the container

• Easily compressable

• Weak intermolecular forces

• Particles move freely in straight lines

The change of state is dependent on

The temperature of the substance, the intermolecular forces between substances

Sublimation

Solid → gas

Deposition

Gas → solid

2 changes of state between solid and liquid

Melting (solid to liquid) and freezing (liquid to solid)

2 changes of state between liquid and gas

Evaporation/boiling: liquid to gas

Condensation: gas to liquid

Heating/cooling curves

The heating/cooling of a substance, with the temperature taken at intervals and plotted as a curve

Melting point

The point at which a substance is transformed from solid to liquid or vice versa

Boiling point

The point at which a substance turns from a liquid to a gas or vice versa

The temperature of a state change remains constant when

The substance is pure

types of substances

Pure and impure

Elements

Pure substances containing only one group of atoms

compounds

pure substance made up of two or more atoms chemically bonded together

2 types of elements

Metals and non-metals

Properties of metals

• shiny

• Malleable/ductile

• Conducts electricity

• High boiling/melting point

• Solid at room temperature

Properties of non-metals

• liquids solids and gases at room temperature

• Cant conduct electricity

• Brittle

• Dull

How to name ionic compounds

Name of metal + name of non metal ending in -ide

How to name polyatomic ionic compounds

Metal + Polyatomic ion (unchanged name)

Mixtures

Two or more compounds/elements that have been physically combined

Compounds vs Mixtures

• compounds are chemically put together, mixtures are physical

• Compounds are hard to separate, mixtures are easy

• Compounds don’t usually have the same properties as the elements that make them up, mixtures do

• Compounds release or take in energy when they’re formed, mixtures don’t

Types of mixtures

Homogenous, heterogenous, solutions

Homogenous mixtures

Mixtures that look the same physically throughout the mixture. No change in colour, texture, or size of particle (e.g. salt and water, water itself)

Heterogenous mixtures

Mixtures characterised by a physical difference between two layers, in terms of colour, particle size, etc. (e.g. oil and water)

Types of heterogenous mixtures

Suspensions, colloids

Suspensions

Formed when an insoluble solute is added to a solvent. The solute forms a layer either above or below the solvent, creating two distinct layers (e.g. oil and water, ethanol and water)

Colloids

heterogenous mixtures characterized by particles smaller than those of suspensions but larger than solute particles, creates a thick opaque mixture that DOES NOT ALLOW LIGHT THROUGH

Emulsion

A type of colloid in which one liquid is dispersed in another

Types of homogenous mixtures

Solutions

Solution

A homogenous mixture formed from dissolving a solute into a solvent

Solubility

The mass of solute that can be dissolved in 100g of solvent at a specific temperature to produce a saturated solution

3 types of solutions, explain them

Unsaturated: more solute particles can be added to the solvent

Saturated: just enough solute particles have been added to the solvent

Super saturated: obtained when heating, more than enough solute particles have been added to the solvent

Solubility of a substance depends on

The structure of the substance, the temperature of the substance, size of particle

As temperature increases, the solubility of solids

Increases

As temperature increases, the solubility of liquids

Decreases

Manual separatiom

Manual, hand separation of solid heterogenous mixtures based on colour shape and size

Magnetism

The use of a magnet on a mixture containing a magnetically susceptible compoinf

Filtration

The separation of a suspension, an insoluble solute from its solvent, to produce a filtrate

Evaporation

The separation of a soluble solute from a solvent, using differences in boiling point

Crystallisation

The formation of pure crystals through the gentle heating of the solvent, until pure crystals are saturated out of the solution

Sublimation

Separating a mixture that has a compound which sublimes (e.g. Dry ice, ammonium salts)

Simple distillation

The separation of a mixture based on the wide differences in boiling point

Fractional distillation

The separation of a mixture based on similar boiling points

Separating funnel

Separates a suspension through differences in density, one layer forms on top pf another

Centrifugation

Separates mixtures due to density, rotates really fast

Chromatography

Separates ink pigment into different colours based on water solubility. The mobile phase (water) runs up the stationary phase (a chromatogram, paper) and the more soluble the substance is the further it travels up the paper

Decantatiom

Separates an insoluble solid from a solvent. The mixture sits out until layers form and the solvent is allowed to “run off” Or decant

Solvent extraction

Used to separate a mixture in which one compound is soluble in water, ads the other isn’t. The insoluble one can be filtered out using filtration

Steps for extraction of sucrose (explain them)

1. Crushing - sugarcane is cut, crushed and lime juice is extracted from the mills. The rest of the sugarcane (bagasse) is used in the furnaces

2. Precipitation (clarifying station) calcium hydroxide, or lime juice, is added to the slightly acidic juice to neutralize it. the juice is heated so the impurities inside it can filter out.

3. Filtration - the impurities are filtered out, and used as fertilizer

4. Vacuum distillation - the juice is gently heated, so that majority of the water inside the juice is evaporated

5. Crystallisation: the formation of pure sugar crystals as well as molasses with the gentle heating of the substance

6. Centrifugation: separation of the sugar crystals snd the molasses, which is used in alcohol

Matter is made up of:

Atoms, ions and molecules

Ions

atoms with a positive or negative charge

Molecule

Group of atoms

People who contributed to discovering the atom

JJ Thomspon, Ernest Rutherford, Niels Bohr, James Chadwick

Subatomic particles

Protons, neutrons, electrons

Properties of protons

• relative mass of 1

• Located inside nucleus

• Charge of +1

Properties of neutrons

• relative mass of one

• Located inside the nucleus

• Charge of 0

Properties of electrons

• relative mass of 1/1840

• Located outside the nucleus, orbit the nucleus on paths called electron shells

• Charge of -1

Mass number

Number of protons and neutrons of an atom, the number on top to the left of the atom (A)

Atomic number

The number of protons in an element (which is equal to the number of electrons). The number at the bottom left

Number of neutrons formula

Mass number - atomic number

Structure of on atom

Dense nucleus, filled with closely packed neutrons and protons, being orbittef by electrons on valence shells

Electron shells and the max electrons they can hold

First shell:2

Second shell: 8

Third shell: 18

Fourth shell: 32

What happens to shell three after it receives electrons

It acts as if its full, then the electrons go to the fourth dhell, but this only happens for 2 valence electrons

Relative atomic mass

The mass of an element (snd its isotopes) compared to the mass of a carbon 12 atom, which as a mass of 12.00 atomic mass units. Takes into consideration the mass numbers of the isotopes and the percentages that they occupy in a natural sample

relative atomic mass vs mass number

Relative atomic mass takes the mass of ALL the isotopes of an element into consideration, mass number just the mass of the element specifically

Isotopes

Atoms of the same element with the same number of protons (and therefore the same atomic number) and a different number of neutrons (different mass number). They have the same chemical properties as each other

Radioisotopes

Isotopes characterised by their unstable nuclei that spontaneously break up, emitting radiation

3 types of radiation that are emitted

Alpha (helium) particles

Beta (electron) particles

Gamma (high speed) particles

Uses of isotopes

1. Medicine

   • cobalt-60: cancer cells

   • iodine-131: detects diseases in thyroid gland

   • plutonium-238: pacemaker battery

2. Research

   • radioactive phosphorus: measures plant growth

   • carbon-13: monitors plant photosynthesis

3. Carbon 14 dating

   • tells the age of an organism by observing how much carbon 14 is left in the body after radiation

How to tell the period of an element

Number of electron shells

How to tell the group of an element

Number of valence electrons

Types of bonding

Ionic, covalent, metallic

Structure

How atoms of a substance are arranged, responsible for the substance’s physical properties

Lattice

A regular, repeating structure in a bond

A regular, repeating lattice forms a

Crystal

Ionic bonds

The electrostatic force of attraction between negatively charged atoms (anions) and positively charged atoms (cations) created by the transfer of electrons

How are ionic bonds created

The metal atoms transfer their electrons to the nonmetal atoms, making the metals positively charged (as they have more protons than electrons) and the metals negatively charged (as they have more electrons than protons). Positive and negative attract to form ionic compounds

Properties of ionic compounds

• high melting/boiling points

• Dense

• Conduct electricity when molten/aqeuous

• Dissolve in water and polar sinstamved

• Brittle

Why do atoms bond

To become stable like the nearest group 8 element in the periodic table

Metallic bonds

Bonds between metals characterised by a group of positive cations arranged in a lattice structure surrounded by a sea of negative cations moving freely about them

Describe the process of metallic bonding

The metallic atoms give up their electrons, form cations. The group of negative electrons that have been delocalized are attracted to the cations, forming a sea of cations in a regular lattice surrounded by a sea freely moving negative electrons

Metal properties

• high melting/boiling point

• Shiny

• Good conductors of heat

• Malleable/ductile

• Solids at room temperature

• Dense

• Don’t dissolve in water

Alloys

Metallic bond containing two or more different metals lf different types and sizes

Purpose of alloys

Creates stronger metals

Intramolecular bonds

Bonds between atoms of a molecule

Intermolecular bonds

Bonds between molecules

Dipoles

Bonds created between covalent molecules, in which one molecule is bigger than the other, causing the electrons to be attracted to one side more than another. This causes positive and negative dipoles. Temporary

Polar molecules

Molecules that have positive and negative dipoles

Van der waals

formed between covalent bonds of the same molecule. Electrons randomly shift causing temporary areas of positivity and negativity

Ionic lattice

Formed by positive cations and negative anions arranging themselves in a regular repeating pattern which extends in all directions through the solid

Simple covalent crystals

Crystals formed from single covalent bonds joined together by weak intermolecular (dipole or van der waals) forces.

Properties of simple covalent crystals

• lower melting/boiling point

• Soluble in non polar substances

• Don’t conduct electricity

• Exist as a gas at room temperature

Giant covalent compounds

Characterized by large, macromolecules of covalent bonds extending all throughout the structure in a regular, repeating pattern