Demonstrate Understanding of Acids

and BasesScience 1.5 (AS90944)

Specific Learning Outcomes

Name some common acids and basesUse litmus to identify an acid and describe the

colour changeDefine the terms

◦Element◦Atomic number◦Atomic mass /mass number◦ Isotope

Know names & symbols for first 20 elementsDescribe, draw and label diagrams of atomic

structureUse atomic number and mass number to calculate

the protons, neutrons and electronsDescribe the structure of the periodic table

Specific Learning Outcomes

Write electron configs. in diagrammatic and shorthand form

Use electron config. to identify its periodic groupName and write formulae for common compoundsDescribe how positive and negative ions are formedWrite ion formulae and identify protons, neutrons

and electrons in ionsName and write formula of a range of positive and

negative ionsName and write formulae for a range of ionic

compoundsWrite word and balanced symbol equations for a

range of chemical reactions

Specific Learning Outcomes

Use collision theory to describe how chemical reactions occur

Understand what things affect the reaction rate and how

Name and write the formula for hydrochloric, sulfuric and nitric acids, metal oxides, metal hydroxides, metal carbonates and hydrogen carbonates

Use universal indicator to identify acids and basesUse the pH scale to identify acids and basesDescribe and write balanced equations for a

range of reactions including neutralisation, carbon dioxide formation and salt formation

Common acids and bases

Acids:◦ Taste sour◦ Corrode metals◦ Turn litmus red◦ Universal indicator is red to

green

Bases:◦ Taste bitter◦ Feel slippery◦ Turn litmus blue◦ Are: hydroxides, oxides,

carbonates, hydrogen carbonates◦ Universal indicator is green to

blue

Substance Formula Colour in litmus

Acid or Base

Vinegar CH3COOH

Baking soda NaHCO3

Hydrochloric acid HCl

Sodium hydroxide NaOH

Sulfuric acid H2SO4

Nitric acid HNO3

Washing soda Na2CO3

Red

Red

Red

Red

Blue

Blue

Blue

Acid

Acid

Acid

Acid

Base

Base

Base

Atomic Structure

Atoms are the smallest part of an element that can take part in a chemical reaction

They are made up of:◦Protons (+ve charge)◦Electrons (-ve charge)◦Neutrons (no charge)

Protons and neutrons are found in a central nucleus and contribute most of the mass

Electrons spins rapidly around the outside

Atomic number and mass number

Atoms have two properties:◦ Atomic number – The number of protons (smaller)◦ Mass number – The number of protons plus the number of

neutrons (larger)

Using the above for an example we can find the number of protons, neutrons and electrons in chlorine.◦ 17 protons – the atomic number of the atom◦ 18 neutrons – the mass number minus the atomic number◦ 17 electrons – because the atom is neutral, the number of

protons = number of electrons

Electron Config.

The electrons (same as the protons and atomic number) can be represented diagrammatically or in shorthand form

Using the example from the slide before they would be as follows

or Cl 2, 8, 7

Atomic structure Practice

Complete the table below

Element Symbol

Atomic #

Atomic mass

# proto

n

# neutro

n

# electro

n

Electron

configHydroge

nH 1 1 1 0 1 1

    8       8 2, 6

    15          

      32        

        5      

            20  

Element Symbol

Atomic #

Atomic mass

# proto

n

# neutro

n

# electron

Electron

configHydrogen H 1 1 1 0 1 1

 Oxygen O  8  16 8  8  8 2, 6

 Phosphorus

 P 15  31  15  16 15 2, 8, 5 

 Sulfur  S 16  32  16  16  16  2, 8, 6

 Boron  B  5  11 5  6  5  2, 3

 Calcium  Ca  20  40  20  20 20  2, 8, 8, 2

Isotopes

An isotope is different forms of the same element

They are atoms with the SAME number of protons but DIFFERENT numbers of neutrons they therefore have:◦Different mass numbers◦Same atomic number◦Same number of electrons◦Same chemical reactions

Periodic Table

The periodic table shows similarities, differences and relationships between elements

Arranged in rows according to their atomic numberVertical columns = groups

◦ all elements in the same group have the same number of electrons in their outer shell Have similar properties

Horizontal rows = periods◦ Elements in the same period have the same number of

electron shells◦ As you go across a period 1 extra electron is added until the

far noble gases on the right which have 8 (a full outer shell)Metals are on the left and non-metals on the right

Periodic Table

Ions and Ionic bonding

Atoms that have lost or gained electron in a chemical reactions are called IONS

Atoms will gain or lose electrons to fill their outer shell and become more stable

A positive ion (cation) will lose electrons leaving it with an overall positive charge

A negative ion (anion) will gain electrons leaving it with an overall negative charge

Eg Sodium (Na), atomic number 11, electron arrangement 2, 8, 1 will lose the one electron to have a full outer shell (the 2nd)

Chlorine (Cl) atomic number 17, electron arrangement 2, 8, 7 will gain 1 electron to have a full outer shell (the 3rd)

Ions 2

Atoms that do not lose or gain electrons are said to be unreactive (the noble gases)

Some ions are made up of more than 1 element eg:◦Hydroxide OH-

◦Ammonium NH4+

◦Nitrate NO3-

◦Hydrogen carbonate HCO3-

◦Carbonate CO32-

◦Phosphate PO43-

Ions 3

Complete the table

Element Electron Config

Lose or gain ele

How many

Ion formed

Config of ion

Lithium 2, 1 Lose 1 Li+ 2

Hydrogen

Fluorine

Aluminium

Sulfur

Potassium

Element Electron Config

Lose or gain ele

How many

Ion formed

Config of ion

Lithium 2, 1 Lose 1 Li+ 2

Hydrogen 1 Lose 1 H+

Fluorine 2, 7 Gain 1 F- 2, 8

Aluminium 2, 8, 3 Lose 3 Al3+ 2, 8

Sulfur 2, 8, 6 Gain 2 S2- 2, 8, 8

Potassium 2, 8, 8, 1 Lose 1 K+ 2, 8, 8

Ionic Bonding

Ions react together in chemical reactions to form compounds

The positive and negative charges need to balance each other out in order to make a stable compound

Eg:

Ionic Table

 +1 

 +2

 +3

 -1

 -2

 -3

 H+

hydrogen

 Mg²+

magnesium

 A13+

aluminium

 C1-

Chloride

 O²-

oxide

 N3-

nitride

 Na+

sodium 

 Ca²+

calcium

 Fe3+

iron (III)

 OH-

hydroxide

 CO3²-

carbonate

 PO4

-3

phosphate

 K+

potassium 

 Fe²+

iron (II)

   NO3

-

nitrate

 SO4²-

Sulfate

  

  NH4

+

Ammonium  

 Cu²+

copper (II)

   HCO3

-

bicarbonate

 S²-

Sulfide

 

    

 Zn²+

zinc

       

    

 Pb²+

lead

       

Rules for writing and naming ionic compounds

1. Write the positive ion first2. Overall charges must be ‘0’3. Use a subscript number to show the ration

of ions in the compound to remove charges4. Generally ‘ide’ indicates only 1 type of

atom while ‘ate’ indicates an atom combined with oxygen – exception ??

5. When writing formulae with ions involving more than one atom, you must use brackets around the ion

Chemical Reactions

You can tell if a chemical reaction has occurred by…◦Observing changes in

Colour Smell Appearance Temperature Electrical conductivity

◦Noting differences in the physical properties of the reactants and products

◦Testing the chemical appearance of the reactants and products

◦A new product is made

Chemical Reactions

Chemical reactions can occur using different types of reactant. Eg.◦Two different elements

Hydrogen gas and chlorine gas make hydrogen chloride◦A compound and an element

Hydrochloric acid and magnesium makes magnesium chloride and hydrogen gas

◦Two different compounds Copper sulfate and sodium hydroxide make copper hydroxide

and sodium sulfate◦A compound splits into 2 elements

Aluminium oxide turn into aluminium and oxygen ◦A compound splits into 2 compounds

Calcium carbonate makes calcium oxide and carbon dioxide◦A compound splits into an element and a compound

Hydrogen peroxide makes water and oxygen

Chemical equations

A chemical equation is used to summarise what is happening in a chemical reaction

It has reactants on the left and products on the right

These can be written as word equations:

◦Sodium + sulfuric sodium sulfate + Hydroxide acid water

Or Formula equations (these should be balanced)◦2NaOH + H2SO4 Na2SO4 + H2O

Chemical Equations 2

Steps to follow to write a balanced equation

1. Write down the names of the reactants and products

Hydrogen + oxygen water2. Write down the correct formula for the reactants

and products H2 + O2 H2O

3. Balance the equation by putting numbers in front of each reactant and product

2H2 + O2 2H2O

Collision Theory

The particle theory state that all substances are made or particles – atoms, ions or molecules.

Chemical reactions take place when the particles of the reactant collide with one another with sufficient energy to react and form product particles

As the reactants turn into product, the rate of the reaction slows.

Eventually one or both of the reactants are all converted to product and the reaction stops

Rate

of

reacti

on

Factors affecting Reaction rate

Reactions of Acids and bases

When ever an acid reacts it forms a salt plus other products

The name of the salt depends on the acid reacting◦Hydrochloric acid ______ Chloride◦Nitric acid ______ Nitrate◦Sulfuric acid ______ Sulfate

Neutralisation

This is the reaction of an acid and a baseIt produces a product with a pH of 7 (neutral)The general reaction is:

Acid + Base Salt + Water

Oxides and Hydroxides is also a neutralisation with the reaction being Acid + Oxide Salt + Water Acid + Hydroxide salt + water

Carbonates or hydrogen carbonates react with acids also but in these reactions Carbon dioxide is also produced Acid + carbonate Salt + Water + Carbon dioxide Acid + hydrogen carbonate salt + water +carbon dioxide