Level 1 Science Acids and Bases

Year 11 100 Science4 External Credits

AS90944Ms Gibellini

Aspects of acids and bases will be selected from:

Atomic structure

electron arrangement of atoms and monatomic ions of the first 20 elements (a periodic table will be provided)

isotopes

ionic bonding

names and formulae of ionic compounds using a given table of ions.

Properties

acids release hydrogen ions in water

reactions (of acids with bases) to form salts.

pH and effects on indicators.

Rates of reaction and particle theory.

Uses

neutralisation

carbon dioxide formation

salt formation.

Acids and bases are restricted to HCl, H2SO4, HNO3, metal oxides, hydroxides, carbonates and hydrogen carbonates. Other acids may be included in examination questions. The names and formulae of any such acids will be given in the question.

Recall the structure of atoms in terms of a central nucleus containing protons and neutrons and surrounded by electrons.

Recall that almost all the mass of an atom is concentrated in the nucleus and that the rest of the atom is almost empty space.

All matter is made up of atoms

Chemistry involves the rearrangement of atoms or groups of atoms

Recall the structure of an atom

Atoms are made up of the following sub atomic particles:

Electrons negative charge

outside nucleus, in shells

constant motion

very very small (1/2000 of a proton)

Neutron No charge, neutral

Inside nucleus

Same size as proton

Proton Positively charged

Inside nucleus

Atoms have an overall neutral charge, therefore:

Number of protons = Number of electrons

Build a model of an atom

Complete worksheets provided

Compete questions 1 &2 on page 75 of workbook

Describe the atomic structure of a lithium atom

Explain how the particles within an atom contribute to its overall mass.

Describe the atomic structure of a lithium atom

Explain how the particles within an atom contribute to its overall mass.

Overall mass of an atom is made up of protons and neutrons, as the mass of electrons is negligible

Define the terms atomic number, mass number and isotope.

Relate the atomic number of an element to its position on the periodic table.

Predict the electron arrangement of an atom from its position on the periodic table for any of the first 20 elements.

Draw a diagram illustrating the structure of a given atom from its atomic number and mass number for any of the first 20 elements

What is the difference between Gold and Oxygen?

Elements are made up of one kind of atom only

Elements have been put in order of:

Physical properties

Chemical properties

Atomic number

Mass number

Number of electrons in outer shell

on the Periodic Table of Elements

Atomic Number:

Smaller number Number of protons Number of electrons

Atomic Mass or Mass Number:

Bigger number of the two Total number of sub atomic particles Number of protons + neutrons.

How do we work out the number of:

Protons = Atomic number

Electrons = Atomic number

Neutrons = Mass number – atomic number

Fill in first 5 columns of Elemental information sheet

An isotope is an atom which exists in more than one form

They have the same number of protons but a different number of neutrons

Electrons arrange themselves in regular order around the nucleus depending on their energy.

Each energy level holds a different number of electrons:

◦ Level 1 – 2 electrons

◦ Level 2 – 8 electrons

◦ Level 3 – 8 electrons

Electrons fill from Level 1 shell, or the closet to the nucleus first.

Fill in columns 9, 10, 11 on elemental information sheet.

Draw dot diagrams for the first 5 elements (use dots for electrons, and draw shell lines in pencil, use blue pen for protons and red for neutrons)

Complete workbook page 77 3C1 and 3C2, page 76 3B2

Lithium atoms can exist in different forms called isotopes. Two of these isotopes are Lithium-6 ( Li ) and Lithium-7 ( Li).

Explain why Li and Li are both neutral atoms. In your answer, you should fully describe their atomic structure and state their electron configuration.

Atomic structure:

Li – 3p, 3n, 3e

Li – 3p, 4n. 3e

Electron configuration:

Both – 2.1

Explanation of neutrality

Both Li isotopes have equal numbers of protons and electrons, ie 3p and 3e. An atom is neutral when it has equal numbers of protons and electrons.

Explain why atoms are neutral, define the term ion and explain why ions are charged particles.

Use the electron structure of an atom to predict the charge on the ion it will form (if any).

Explain in simple terms what an ionic bond is.

Name ions and ionic compounds from their formulas.

Atoms require their outer shells to be full in order to be chemically stable

Atoms either lose or gain electrons to get a full outer shell (2,8,8)

When atoms lose or gain electrons they become electrically charged and are then called ions

Gaining electrons results in a ________ ion

Loosing ions results in a __________ ion

The number of protons stays the same

E.g

Na Na+ + e-

Sodium atom sodium ion Free electron2, 8, 1 2, 8,

Cl + e- Cl-

Chlorine atom electron Chlorine ion2, 8, 7 2, 8, 8

The charge on an ion is called its valency.

Valency always has a sign (+ or -) and a numerical value. (although we don’t write 1)

Complete ion information on elemental sheet

Ionic compounds:

Electrons move to create stable ions

Made up of metal and non metal

Named by the ions they contain

If oxygen involve – ate, otherwise end in -ide

NaCl = sodium chloride

How do you know if an atom will gain or lose electrons?

Eg. Na 2,8,1- is it easier to lose one electron or gain 7?- Hence Na looses a negative electron to become: - Na+

Eg. Cl 2,8,7- is it easier to gain one electron or lose 7?- Hence Cl gains a negative electron to become: - Cl-

Complete page 79 3D1,

Magnesium and calcium atoms both form ions with a charge of +2. Magnesium atoms form Mg2+ ions, and calcium atoms form Ca2+ ions.

Explain why magnesium and calcium atoms form ions with the same charge of +2. In your answer, you should: define an ion explain why atoms form ions identify the group on the periodic table where

the two atoms are found explain why both magnesium and calcium ions

have a charge of +2.

Definition of an ion:An ion is an atom or group of atoms that have lost or gained an electron and therefore carry a charge.Explanation of formation of ions:If the outer shell (valence) of an atom is not filled, the atom is unstable. It will react to gain a full outer shell to become more stable, by either losing or gaining electrons and making it into an ion.Identification of Group: Magnesium and calcium are in the same group on the periodic table (Group 2). Explanation of why both form+2 ions:The atoms have the same number of electrons (two) in their outer shell. (Students may give the electron configuration instead.)Both Mg and Ca need to lose two outer electrons to become stable by having a full outer shell. Each ion (Mg2+ and Ca2+) ends up with two less electrons than there are protons in its nucleus, so the ion has a charge of +2.

Explain why ions combine in the ratios they do in ionic formulas.

Write the formula for a given ionic compound given a table of ions.

Count atoms in a given chemical formula.

Ionic compounds have an overall neutral charge.

Therefore there must be equal numbers of positive and negative charges.

◦ Magnesium Nitrate Mg2+NO3-1

Mg+ Mg+ NO3-1

◦ 2 positives and one negativeswhat is needed to balance the charges?

◦ Another negative or (NO3-1)2

Mg2+(NO3-1)2 - we need another whole anion so use brackets

Formulas show how many atoms of each type are in a compound

The bottom right hand number tells us how many of the atom directly before there are.

◦ H20 = 2 hydrogen atoms, one oxygen atom

We don’t write 1 in as we are lazy!

The number directly outside a bracket is a multiplier of everything inside the bracket.

◦ Al(OH)3 = 1 Al, 3 O, 3 H

◦ (NH4)3PO4 = 3N, 12 (3x4) H , 1P, 4 O

To get the total number of atoms we work out how many of each atoms there are and then add them

◦ (NH4)3PO4 = 3N, 12 (3x4) H , 1P, 4 O

◦ 3+12(3x4)+1+4 = 20 atoms

A big number in front means two of the whole compound – so work out how many of each atom there is, add them up and then multiply this by the big number at the front.

◦ 2(NH4)3PO4 = 3N, 12 (3x4) H , 1P, 4 O

◦ 3+12+1+4 = 20 atoms

◦ 20 x 2 = 40 atoms

Complete pages 80-84 3E1, 3E2, 3E3, 3E4, 3E5

Explain why the ions in sodium hydroxide combine to give the formula NaOH but the ions in beryllium hydroxide combine to give the formula Be(OH)2.

In your answer, you should:

compare the charges on the individual ions found in the compounds sodium hydroxide and beryllium hydroxide

explain why the ions combine in the ratios the way they do to form the compounds NaOH and Be(OH)2.

Comparison of charges on ions:

When these elements react, Na loses one electron and forms a +1 ion, while Be loses two electrons and forms a +2 ion in order to adopt the stable electron configuration. The hydroxide carries a charge of -1.

Explanation of formation of compounds:

An ionic compound is electrically neutral therefore all the positive charges must balance the negative charges.

Therefore it requires one OH-1 for each Na+ ion but two OH-1 ions for each Be2+ ion to form a neutral compound/ balance the charges.

Explain why the ions formed by sodium and oxygen both have the same electron arrangement. In your answer you should:• describe an ion• describe the atomic structures of a sodium ion and an oxide ion • state the charge on the sodium ion and the oxide ion• explain the charges on both ions in terms of electron arrangement and number of protons

Element X is between numbers 11 and 18 on the Periodic Table. An atom of element X forms an ion. This ion combines with the hydroxide ion to form a neutral compound, X(OH)3.

Determine what element X is and justify your answer.

In your answer you should:• consider the ratio of X ions to hydroxide ions • use the formula X(OH)3 to determine the charge of the X ion • explain how you would use the Periodic Table in your Resource Booklet to find out which group element X is in • name element X.

Recall the characteristic properties of acids and bases including concentration of H+ and/or OH–.

Recall the names and formulas for hydrochloric acid, nitric acid and sulfuric acid.

Recall the colour changes of litmus or universal indicator in acidic, basic and neutral solutions.

Recall the acid-base character of common household substances such as vinegar and baking soda.

Substance Acid (red/orange)

Base (purple/blue)

Neutral(green)

Taste sour pH less than 7

Turn litmus red Contain hydrogen ion H+

Conduct electricity

Acid rain (oxides of sulphur and nitrogen from factories dissolve in water to form acid rain)

citric juice, stomach acid (HCl), vinegar, battery acid

Acid reactions:◦ Acid + base salt + water◦ Acid + metal salt + hydrogen gas◦ Acid + carbonate salt + water + carbon dioxide

Taste bitter, Feel slippery pH greater than 7 Turn litmus blue Alkali is a base that is soluble in water Metal oxides and metal hydroxides Most contain OH- ion, hydroxide ion Conduct electricity Soaps, oven cleaners (NaOH) Antacids (Mg(OH)2) – neutralise stomach acids Floor cleaners, bleach (ammonium hydroxide) Calcium hydroxide is limewater Calcium hydrogen carbonate – limestone caves Used to neutralise acids:◦ Neutralisation ◦ HCl + NaOH NaCl + H2O = pH 7

Common Name Chemical Name

Formula Acid Base

Vinegar

Lemon juice

Grape juice

Soda Water

Antacids

Floor Cleaner

Battery Acid

Stomach Acid

Nitric Acid

Hydrochloric Acid

Magnesium oxide

Common Name Chemical Name Formula Acid Base

Vinegar Acetic Acid C2H4O2

Lemon juice Citric Acid C6H8O7

Grape juice Tartaric Acid C4H6O6

Soda Water Carbonic Acid H2CO3

Antacids Magnesium Hydroxide MgOH

Floor Cleaner Ammonium Hydroxide NH4OH

Battery Acid Sulphuric Acid H2SO4

Stomach Acid Sulphuric Acid H2SO4

Nitric Acid Nitric Acid HNO3

Hydrochloric Acid Hydrochloric Acid HCl

Magnesium oxide Magnesium oxide MgO

Complete page 85 3F1

List three common household acids and their formulas

List three common household bases and their formulas

Use the pH scale to indicate degree of acidity or basicity.

State that food acids release fewer hydrogen ions in solution than laboratory acids, and relate this to the pH of the solutions formed when different acids dissolve in water.

We use a pH scale to tell us how acidic, basic or neutral a substance is.

Acids have a pH range from 1-6

Alkalis or bases have a pH range from 8-14

Neutral substances have a pH of 7

Strong acids contain more free H+ ions

Strong bases contain more free OH- ions

Most naturally occurring substances are weak eg. Citric acid in citrus fruit

State that when hydroxides dissolve in water they release hydroxide ions which make the solution basic.

State that some hydroxides are more soluble in water than others and relate this to the pH formed when different hydroxides dissolve in water.

Identify metal oxides, carbonates and hydrogen carbonates as substances that react with water to form basic solutions.

Explain why some metal oxides form solutions of high pH and others form solutions of only moderate pH.

Discuss changes in pH or indicator colour during neutralisation reactions.

Name the salts formed by hydrochloric, sulfuric and nitric acids.

Complete word or formula equations for making specific salts.

Apply an understanding of pH and neutralisation reactions to situations in everyday life.

When we add base to an acid, a chemical reaction takes place.

The acid and base are used up in the reaction.

We say they are neutralised. They make a salt and water.

When a substance has been neutralised or is neutral it has a pH of around 7.

Acid + Base Salt + Water

Aim: To neutralise an acid using a base.

Method:

Step 1: Add four drops of sodium hydroxide to a test tube.

Step 2: Add one drop of universal indicator to the test tube and shake.

Step 3: Stop when the solution is green, if the solution turns red or orange add a very small drop of NaOHuntil the liquid turns green.

What causes indigestion?

-to much acid in the oesophagus

What do we need to add to neutralize that acid?

- Base! – Antacid, quieeze, mylanta etc

Complete Experiment on page 255 of Science World 10. ◦ Record Aim and Table for results.

◦ Copy and complete questions and conclusions

Iron Magnesium Zinc Copper Lead

HydrochloricAcid

SulphuricAcid

Zinc SulphateZnSO4

H2 Formed

NoReaction

NitricAcid

Salts are named after the acids from which they are formed.• Hydrochloric acid forms chloride salts• Sulphuric acid forms sulphate salts• Nitric acid forms nitrate salts

Complete pages 88 3G1 and 3G2, page 95

A student puts 5 mL of dilute hydrochloric acid into a boiling tube and adds five drops of universal indicator to the solution. The student then takes a solution of sodium hydroxide of the same concentration as the acid and adds it one drop at a time to the acid until the colour stops changing.

Describe the colour of the universal indicator solution:

◦ in the hydrochloric acid before any sodium hydroxide was added.

◦ when the sodium hydroxide was added and the colour of the solution stopped changing.

As the sodium hydroxide is added several colour changes occur.

Explain how the colour changes relate to pH AND what ions are present in the solution colour changes.

Description of colour changes:

red / pink to start with

blue / purple / violet at end.Explanation of colour changes:

At the beginning the red indicated a low pH due to excess H+ ions in the solution.

As the NaOH was added, a yellow / green colour indicates a pH of around 7, due to the OH- ions combining with the H+ ions to form a neutral solution.

As more NaOH is added the blue / purple indicated a pH of 11 plus, due to excess OH- ions in the solution.Identification of reaction type:

Acid-base (or acid-carbonate) neutralisation (the carbonate ions react with the H+

ions of the acidic solution and neutralise the solution).

Description of observations:

Bubbling in the solution / fizzing / effervescence / frothing / foaming Ca2CO3

disappears.

Linking observations to products:

The products are CO2, H2O and a salt. The CO2 gas causes the bubbles / fizzing / etc.

Writing a word equation:

Nitric acid + sodium carbonate sodium nitrate + water + carbon dioxide

Writing a symbol equation:

2HNO3 + Na2CO3 2NaNO3 + H2O + CO2

A student put 10 ml of dilute nitric acid in a boiling tube with five drops of universal indicator. Sodium hydroxide of the same concentration was then added. The following observations were recorded.

Discuss the reaction occurring as sodium hydroxide is added to the nitric acid.

In your answer you should:

• explain the relationship between the colours observed and the pH of the solution

• explain which ions cause the different colours of the solution

• write a word equation for the reaction AND a balanced symbol equation for the reaction.

Identify metal oxides, carbonates and hydrogen carbonates as substances that react with water to form basic solutions.

Explain why some metal oxides form solutions of high pH and others form solutions of only moderate pH.

Write word and balanced formula equations for reactions between acids and metal hydroxides, oxides, carbonates or hydrogen carbonates.

Describe the visible effect of adding acid to a carbonate or hydrogen carbonate.

Describe the limewater test for carbon dioxide and write balanced equations for the two reactions that occur during this test.

Reactant Product

There has to be the same number and type of each atom on both sides of the arrow –this is how you check you have balanced the equation correctly!

There are three types of equations

◦ Word equations (don’t need atoms balanced)◦ Symbol equations◦ Ionic equations (not need for level 1)

Step 1: Write out word equation

Magnesium + oxygen Magnesium oxide

Step 2: Write out symbol formula

Mg + O2 MgO

Step 3: Count atoms of each kind on each side

1 Mg 2 O 1 Mg 1O

Step 4: Identify the atoms with different numbers

2 oxygen atoms on left one on right

Step 5: Increase atoms by putting number:

in front of compound (2H2O) – makes 4 H & 2 O

after an ion (Mg2) – makes 2 Mg

brackets and a subscript around polyatomic ions (SO4)2 –makes 4 S & 8 O

Do hydrogen then oxygen atoms first

Mg + O2 2MgO

Step 6: Count atoms of each kind on each side –

they will have changed as a result of step 5!!!!

1 Mg 2 O 2 Mg 2O

Step 7: Identify the atoms with different numbers

1 Mg on left & 2 on right

Step 8: Increase atoms numbers

2Mg + O2 2MgO

Step 9: Count atoms of each kind on each side

1 Na 4H 2 O 2 Na 2 O 4H

Step 10: Identify the atoms with different numbers

1 Na on left and 2 on right

Step 11: Increase atoms numbers

2Na + 2H2O 2NaOH + H2

Step 12: Count atoms of each kind on each side

2 Na 4H 2 O 2 Na 2 O 4H

Same type of atoms and same number of atoms on both sides – DONE!

Nobody said it’d be easy but it does get easier, and remember practice makes perfect!

Acid + Base Salt + Water

Hydrochloric acid + sodium hydroxide

sodium chloride + water

Test to see if reaction is complete by using indicator – solution should turn

Green

Acid + Carbonate

Salt + Water + Carbon dioxide

Sulphuric Acid + Copper Carbonate

Copper sulphate + water + Carbon dioxide

We test for Carbon dioxide by bubbling the gas into lime water which turns

milky

Acid + Metal Salt + Hydrogen Gas

Nitric Acid + magnesium

magnesium nitrate + hydrogen gas

We test for hydrogen gas by doing the

POP test

Acid + Base Salt + Water

Acid + Carbonate

Salt + Water + Carbon dioxide

Acid + Metal Salt + Hydrogen Gas

Acid + Metal Oxide Metal Salt + Water

Acid + Metal Hydroxide Metal Salt + Water

Acid + Metal Carbonate Metal Salt + Water + Carbon Dioxide

Acid + Metal Hydrogen Carbonate Metal Salt + Water + Carbon Dioxide

Acid + Ammonia Solution Ammonium Salt + Water

A student wanted to make the salt, magnesium chloride.

Discuss how the student would make magnesium chloride salt from hydrochloric acid and magnesium oxide.

In your answer you should:• state what type of reaction occurs• write a word equation AND a balanced symbol equation for the reaction between hydrochloric acid and magnesium oxide• explain how you would make magnesium chloride in a school lab from hydrochloric acid and solid magnesium oxide (this can be done by drawing labelled diagrams).

Type of reactionAcid-Base reaction or neutralisation.

Word Equationhydrochloric acid + magnesium oxide → magnesium chloride + water.

Balanced Equation2HCl + MgO → MgCl2 + H2O

How to make itAdd magnesium oxide to hydrochloric acid in a beaker. Heat slightly and pour this into an evaporating dish and leave somewhere warm (e.g. window sill) for a few days or heat over Bunsen to speed up the reaction, so that the water can evaporate, leaving magnesium chloride salt. Safe lab procedure would include dealing appropriately with chemicals such as HCl or the wearing of safety glasses

Design and carry out controlled experiments into the factors that affect the rate of a reaction.

Summarise the principles of particle theory. State that as the size of the pieces decreases, the total

surface area increases. Describe what would be observed when a controlled

investigation into how the size of the pieces affects reaction rate is carried out.

Apply particle theory to explain the effect of the size of the pieces on reaction rate.

Explain the meaning of the terms concentrated and dilute in terms of particles in a solution.

Describe what would be observed when a controlled investigation into how concentration affects reaction rate is carried out.

In order for a reaction to occur particles need to collide

Particles need to collide with enough force to break bonds and form new ones

The more successful collisions the faster a reaction occurs

Complete Rates of Reaction Experiments

More successful collisions can be caused by:

◦ Increasing the temperature (particles move faster so collide more)

◦ Increasing the concentration (more particles to collide)

◦ Increasing surface area (small particles have greater surfaces for collisions to occur)

◦ Use a catalyst (holds chemicals so collisions can occur, lowers activation energy needed to break bonds)

◦ Increase pressure (particles are closer together therefore collide more often)

Increasing collisions increases rate of reaction!

Complete Rates of Reactions Experiments

Complete worksheets

Complete pages 98-103 (all the equipment you need is up the front)

Calcium carbonate (marble chips) and hydrochloric acid react together in a conical flask.The word equation for this reaction is:

calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide gas

(a) Describe an observation you would make when this reaction occurs.

(b) Explain why the mass decreases with time.

When more concentrated hydrochloric acid is used, the reaction is faster. Explain the difference in the rate of reaction. In your answer you should refer to: • particles • collisions • reaction rate.

Fizzing / bubbling occurs, marble chips decrease in size, heat is produced.

Why mass decreasesThe marble chips decreases as one of the products is CO2 gas. This gas escapes and so the mass of the flask and contents is reduced.

What’s happeningAs the reactant particles collide, they form product particles. As the reaction proceeds, there are fewer and fewer reactant particles left to collide and so the rate of reaction becomes slower.

At the start (section X) of the reaction, more product particles are being formed, then more gas is being formed, therefore more gas escapes at first and so the mass of the flask and contents decreases more rapidly. At X, the rate of reaction is fast but decreasing with time.

In section Y there are now fewer (less) reactants and so there are fewer collisions per second (unit time) and so less product is formed, ie less gas being released, so the mass does not decrease as rapidly. At Y, the rate of reaction is slow and slowing.

In section Z the reaction has stopped, as one of the reactants (marble chips or HCl) has run out, so there are no particles left to react.

When more concentrated acid is used, there are more acid particles in the same volume of the acid. Because of this, there are more particles to collide with the calcium carbonate. Because there are more to collide, the rate of reaction is faster.

Explains why the reaction is faster, by linking the idea that there are more acid particles in the same unit volume available for collisions, and hence there will be more collisions, causing the faster reaction rate