Chemistry - Principles of Chemistry

Principles of Chemistry

Arrangements of solid particles

in neat rows and packed closely

movement of solid particles

vibrate only

energy of solid particles

less kinetic energy

arrangement of liquid particles

mostly touching but random arrangement

movement of liquid particles

nove and slide over each other

energy of liquid particles

more/greater kinetic energy

arrangement of gas particles

far apart and random

movement of gas particles

move randomly at high speeds

energy of gas particles

high kinetic energy

solid to liquid

melting

liquid to gas

evaporation

gas to solid

deposition

solid to gas

sublimation

gas to liquid

condensation

liquid to solid

freezing

diffusion

the net movement of particles from an area of high concentration to an area of low concentration until a mixture is formed; it takes place in gases and liquids where the particles are free to move.

Diffusion experiment 1

potassium permanganate crystal placed in a beaker will over time naturally dissolve and then diffuse to make a uniform purple solution

diffusion experiment 2

bromine is placed in a gas jar and a second gas jar is placed above - once released the bromine diffuses into the top gas jar and a mixture is formed

Gravity stops/affects diffusion. True or False

False

Diffusion experiment 3

concentrated ammonia (NH3) and hydrochloric acid (HCl) are soaking in cotton wool and placed at opposite ends of a long glass tube. NH3 and HCl gas molecules diffuse towards each other reacting to make a white ring of solid ammonium chloride (NH4Cl) [ NH3(g) + HCl(g) → NH4Cl(s) ] The white ring always forms nearer the HCl end because NH3 molecules are lighter tha HCl therefore diffuse faster and travel further than the HCl molecules.

Dilution experiment (diffusion experiment 4)

take a small amount of a coloured solution and add water several times, the solution gets paler and paler as there are less coloured particles in the same volume of liquid.

Why does diffusion take minutes when the gas particles are travelling very fast?

Diffusion takes time because the gas particles are colliding with each other, the walls of the container and air particles.

solute

the solid that dissolves

solvent

the liquids that the solid dissolve in

solution

the mixture formed when a solid dissolves in a liquid

saturated solution

a solution which contains as much dissolved solid as possible at a particular temperature.

element, compound or mixture

element

element, compound or mixture?

mixture

element, compound or mixture?

compound

element, compound or mixture?

compound

element, compound or mixture?

mixture

element, compound or mixture?

Element

element, compound or mixture?

compound

element, compound or mixture?

element

element, compound or mixture?

mixture

elements

elements are made up of just one type of atom

compounds

compounds are made up of two or more types of atom chemically bonded together in fixed proportions

mixture

a mixture is a number of elements and/or compounds mixed but not chemically joined

example of an element

carbon (C), hydrogen (H2), iron (Fe)

example of a compound

carbon dioxide (CO2), water (H20), calcium chloride (CaCl2)

example of mixture

eg air, sea water, crude oil

pure substances

melt or boil at a single fixed temperature

impure substances

tend to melt or boil over a range of temperatures

simple distillation

the separation of water and a soluble salt

simple distillation apparatus name

condenser

simple distillation apparatus process

condenser is heated, the water boils first and water vapour then travels down the cold condenser turning it back into liquid water for collection. The salt (NaCl) remains behind as it never reaches its boiling point. (water goes in the bottom and out of the top of the condenser so that it remains filled with water for better cooling.

fractional distillation

the separation of mixtures of liquids

examples of mixtures that could be fractionally distilled

ethanol, alchohol, water, crude oil

what helps with the separation of substances with similar boiling points?

fractionating column

how does the fractionating column help with the separation of substances with similar boiling points?

one substance is collected first at one temperature, the flask is switched as the temperature rises and the next substance is collected.

filtration

the method to separate an insoluble solid from a liquid

an example where filtration would be needed

removing sand from water

residue

the insoluble solid left in the filter paper eg sand

filtrate

the liquid collected e.g water

crystallisation

the method used o separate a solute (soluble solid) from a solution

an example where crystallisation would be used

sodium chloride crystals from a sodium chloride solution

crystallisation process (4 points)

1. solution is heated in an evaporating dish to remove some water

2. the solution is cooled and crystals form

3. he mixture is filtered to collect the crystals

4. crystals are dried on filter paper

chromatography

the method used to separate inks, dyes and food colourings

In chromatography the more ______ inks travel further up the paper, separating them out.

soluble

chromatography process (5 points)

1. a pencil line is drawn across the chromatography paper 1cm from the bottom

2. spots of the mixture of dyes are put on the pencil line and allowed to dry

3. the paper is lowered into a beaker with a little solvent (usually water), the paper must be touching the solvent but the spots must be above

4. when the solvent nearly reaches the top, the paper is taken out and where the solvent has got to, you mark the ‘solvent front’

5. the paper is left to dry

why must the inks not be in the solvent at the start

they will just dissolve in the solvent and not travel up the paper

why do we use a pencil line

the pencil is insoluble in most solvents (water) and will not move up

Rf value equation

Rf = distance moved by dye / distance moved by solvent

how to find Rf value (chromatography - 3 points)

1. measure the distance from the pencil line to the centre of the spot to nearest mm

2. measure the distance from pencil line to solvent front

3. use equation

atom

the tiny particles that make up all matter

molecules

a group of chemically bonded atoms (can be an element or a compound)

relative mass of a proton

1

relative mass of a neutron

1

relative mass of an electron

1/1836

relative charge of a proton

+1

relative charge of a neutron

0

relative charge of an electron

-1

atomic number

number of protons in an atom

mass number

number of protons and neutrons in an atom

what kind of atoms always have the same number of protons and electrons

neutral

isotopes

atoms of the same element that have the same number of protons but a different number of neutrons

relative atomic mass (Ar)

the average mass of the isotopes of the element relative to the mass of 1/12th of a 12C atom

relative atomic mass equation

((mass number x %) + (mass number x %)) / 100

are the groups vertical or horizontal columns?

vertical columns

True or False? The periods are the horizontal columns of the periodic table.

True

how many electrons can fit into the first shell?

2

True or False? the second, third and fourth shells all fit up to 8 electrons

False, only the second and third fit up to 8

how many electrons can the fourth shell fit?

18

are metals good or bad conductors of electricity?

good

are metal oxides acids, alkalis or bases?

bases

are non-metal oxides acidic, alkaline or bases?

acidic

what does the group number represent

the number of electrons in the outer shell of the atom

what does the period number represent?

the number of shells

why do elements in the same group all react in a similar way?

because they have the same number of outer shell electrons

what is the name for the group 0 elements

noble gases

what does inert mean? which group is inert?

inert means undergoing almost no chemical reactions. Group 0 (the noble gases) is inert

why are the noble gases (group 0) inert

because their atoms have full outer shells of electrons which is a very stable electronic configuration

why is argon used in light bulbs

to stop the metal filament reacting with oxygen that would be present in the air

what must be kept the same in balancing equations

there must be the same number and types of atoms on both sides of a chemical equation as atoms are not created or destroyed in chemical reactions

relative formula mass (Mr)

the mass of a compound or molecule compared to Carbon-12

a mole

a unit of the amount of a substance

what is the equation to find Moles

Moles = mass/mr

actual yield

the amount of product you actually get

theoretical yield

the amount of product that your calculations say you should get if the reaction was perfect

yield equation

% yield = (actual yield / theoretical yield) x 100