Access to HE Diploma Pharmacy and Biomedical Science Introduction to Matter Lesson 5

Hand in homework Moles, Formulae and Equations workbook.

Assessment Criteria 1.1 Define an element giving examples. 1.2 Write the names and symbols of the first 20 elements. 1.3 Describe and explain what some of the general physical properties of metals and non-metals are 1.4 Describe the relative position of metals, non-metals, groups and periods within the periodic table with examples. 2.1 Classify substances as elements or compounds from their names giving examples 2.2 Describe two differences between a compound and a mixture 3.1 Describe protons, neutrons and electrons in terms of their relative charges and relative masses. 3.2 Describe the distribution of mass and charge within an atom. 3.3 Describe the contribution of protons and neutrons to atomic nuclei in terms of atomic number and mass number. 3.4 Deduce the electronic configurations of atoms up to z = 36 and ions, given the atomic number and charge, limited to s and p blocks up to Z= Describe ionic bonding as the electrostatic attraction between two oppositely charged ions including dot and cross diagrams. 4.2 Describe a covalent bond as a pair of electrons shared between two atoms 4.3 Write the formulae for some simple and some complex compounds 4.4 Describe and interpret and/or predict physical properties in terms of the types motion and arrangement of particles (atoms, molecules and ions) and the forces between them, and the different types of bonding. 5.1 Describe an acid as a species that can donate a proton. 5.2 Describe a base as a species that can accept a proton 5.3 Describe the reaction of an acid typified by hydrochloric acid with metals, carbonates bases and alkalis and interpret them using ionic equations to emphasise the role of H + (aq) 5.4 Write a balanced equation for the reaction between two elements and between an acid and a base 6.1 Construct balanced chemical equations, full and ionic

Review Activity Draw a diagram (using dots or crosses) to show the bonding in magnesium chloride. Include ALL the electrons in each species and the charges present.

Review Activity (b) Carbon forms an oxide called Carbon Dioxide, CO 2. The bonding in Carbon Dioxide can be represented as: O=C=O Complete the diagram below for the CO 2 molecule using dots or crosses to represent electrons. Just show all of the outer shell electrons. O CO

Review Activity Define an ionic bond Define a covalent bond

Today’s Aim Appreciate that some compounds, e.g. oxides, can be acidic or basic

Week Describe an acid as a species that can donate a proton. 5.2 Describe a base as a species that can accept a proton 5.3 Describe the reaction of an acid typified by hydrochloric acid with metals, carbonates bases and alkalis and interpret them using ionic equations to emphasise the role of H + (aq) 5.4 Write a balanced equation for the reaction between two elements and between an acid and a base

Week 5 Reading Access to Chemistry Alan Jones, Mike Clement, Avril Higton Elaine Goulding ISBN Inside the atom Pages

5.1 Describe an acid as a species that can donate a proton. Acid Definition Any of a class of substances whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to react with bases and certain metals to form salts. A substance that yields hydrogen ions when dissolved in water. A substance that can act as a proton donor. A substance that can accept a pair of electrons to form a covalent bond

5.2 Describe a base as a species that can accept a proton Definition of a base Any of a class of compounds whose aqueous solutions are characterized by a bitter taste, a slippery feel, the ability to turn litmus blue, and the ability to react with acids to form salts. A substance that yields hydroxyl ions when dissolved in water. A substance that can act as a proton acceptor. A substance that can donate a pair of electrons to form a covalent bond.

Acids and Bases Acids have a pH of less than 7. Bases have a pH of more than 7. When bases are dissolved in water, they are known as alkalis. Salts are made when an acid reacts with a base, carbonate or metal. The name of the salt formed depends on the metal in the base and the acid used. For example, salts made using hydrochloric acid are called chlorides.

Acids Substances with a pH of less than 7 are acids. The stronger the acid, the lower the pH number. Acids turn blue litmus paper red. They turn universal indicator red if they are strong, and orange or yellow if they are weak.

Bases Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides. For example, copper oxide and sodium hydroxide are bases.

Alkalis Bases that dissolve in water are called alkalis. Copper oxide is not an alkali because it does not dissolve in water. Sodium hydroxide is an alkali because it does dissolve in water. Alkaline solutions have a pH of more than 7. The stronger the alkali, the higher the pH number. Alkalis turn red litmus paper blue. They turn universal indicator dark blue or purple if they are strong, and blue-green if they are weak

Neutral solutions Neutral solutions have a pH of 7. They do not change the colour of litmus paper, but they turn universal indicator green. Water is neutral.

5.3 Describe the reaction of an acid typified by hydrochloric acid with metals, carbonates bases and alkalis and interpret them using ionic equations to emphasise the role of H + (aq) When acids react with bases, a salt and water are made. This reaction is called neutralisation. In general: acid + metal oxide → salt + water acid + metal hydroxide → salt + water Remember that most bases do not dissolve in water. But if a base can dissolve in water, it is also called an alkali.

Carbonates When acids react with carbonates, such as calcium carbonate (found in chalk, limestone and marble), a salt, water and carbon dioxide are made. In general: acid + metal carbonate → salt + water + carbon dioxide Notice that an extra product - carbon dioxide - is made. It causes bubbling during the reaction, and can be detected using limewater. You usually see this reaction if you study the effects of acid rain on rocks and building materials

Reactive metals Acids will react with reactive metals, such as magnesium and zinc, to make a salt and hydrogen. In general: acid + metal → salt + hydrogen The hydrogen causes bubbling during the reaction, and can be detected using a lighted splint. You usually see this reaction if you study the reactivity series of metals.

Acids, alkalis and neutralisation When atoms or groups of atoms lose or gain electrons, charged particles called ions are formed. Ions can be either positively or negatively charged. For the Higher grades, you need to know which ions are produced by acids, and which are produced by alkalis. You will also need to know the ionic equation for neutralisation.

Acids When acids dissolve in water they produce hydrogen ions, H +. For example, looking at hydrochloric acid: HCl(aq) → H + (aq) + Cl - (aq) Remember that (aq) means the substance is in solution

Alkalis When alkalis dissolve in water they produce hydroxide ions, OH -. For example, looking at sodium hydroxide: NaOH(aq) → Na + (aq) + OH - (aq) Ammonia is slightly different. This is the equation for ammonia in solution: NH 3 (aq) + H 2 O(l) → (aq) + OH - (aq) Be careful to write OH - and not Oh -.

Neutralisation reaction When the H + ions from an acid react with the OH - ions from an alkali, a neutralisation reaction occurs to form water. This is the equation for the reaction: H + (aq) + OH - (aq) → H 2 O(l) If you look at the equations above for sodium hydroxide and hydrochloric acid, you will see that there are Na + ions and Cl - ions left over. These form sodium chloride, NaCl.

Naming salts You need to be able to work out which particular salt is made in a reaction. You may be asked to describe how to make a salt. The name of a salt has two parts. The first part comes from the metal in the base or carbonate, or the metal itself if a reactive metal like magnesium or zinc is used. The second part of the name comes from the acid used to make it. The names of salts made from hydrochloric acid end in -chloride, while the names of salts made from sulfuric acid end in -sulfate.

5.4 Write a balanced equation for the reaction between two elements and between an acid and a base MetalAcidSalt sodium hydroxide reacts withhydrochloric acidto makesodium chloride copper oxide reacts withhydrochloric acidto makecopper chloride sodium hydroxide reacts withsulfuric acidto makesodium sulfate zinc oxidereacts withsulfuric acidto makezinc sulfate

1. A solution has a pH of 4 - what does this mean? It is acidic. It is neutral. It is alkaline. 2. Which of the statements below is correct? Bases are acids that dissolve in water. Bases are alkalis that dissolve in water. Alkalis are bases that dissolve in water. 3. A liquid has a pH of 7. What does this tell you about the liquid? It is water. It is sodium chloride solution. It is neutral.

4. Which salt is made when calcium carbonate reacts with hydrochloric acid? sodium chloride calcium chloride calcium sulphate 5. Which pair of substances will react together to make copper sulfate? copper and sulfuric acid copper oxide and sulfuric acid copper oxide and hydrochloric acid 6. Which is the correct order of methods for making a salt from an acid and an insoluble base? filtration ==> evaporation ==> neutralisation neutralisation ==> evaporation ==> filtration neutralisation ==> filtration ==> evaporation

Review Week Describe an acid as a species that can donate a proton. 5.2 Describe a base as a species that can accept a proton 5.3 Describe the reaction of an acid typified by hydrochloric acid with metals, carbonates bases and alkalis and interpret them using ionic equations to emphasise the role of H + (aq) 5.4 Write a balanced equation for the reaction between two elements and between an acid and a base

Workbook Complete section 6c pages

Next Week Access to Chemistry pages Describe ionic bonding as the electrostatic attraction between two oppositely charged ions including dot and cross diagrams. 4.2 Describe a covalent bond as a pair of electrons shared between two atoms 4.3 Write the formulae for some simple and some complex compounds 4.4 Describe and interpret and/or predict physical properties in terms of the types motion and arrangement of particles (atoms, molecules and ions) and the forces between them, and the different types of bonding.