Chapter 1 : Chemical Reactions of Metals

Introduction to Chemical Reactions of Metals

In your everyday life, you use metals; for example, in jewelery, spoons, sauce pans, or cars. They have many uses due to their properties which include strength, malleability, conduction of electricity and conduction of heat. Metals can react with water, acid and oxygen. The reactivity of the metal determines which reactions the metal participates in.
In this chapter, you will learn that the reaction of metals can be presented as word equations and understand their application in your daily life.

1.1: Word equations
Chemists after studying chemical reactions, most often make a report. In their report they use equations to summarise the reactions. There are 3 types of equations: word equation, molecular equation and ionic equation. All these equations have the same basic structure. In Activity 1.1, you will discover how to formulate word equations.

Activity 1.1: Formulating word equations
What you need: notebooks, stylus, slate,figure this serkins brailler and braille papers, magnesium ribbon, source of heat, test tube holder.

What to do:

1. Watch a video showing the burning of magnesium ribbon as your teacher interprets the sound in the video using sign language.
2. Hold 4 cm of magnesium ribbon with a test tube holder.
3. Light the magnesium ribbon on a Bunsen flame. Note your observations.
4. Wash your hands with clean water and soap.
   In small groups, discuss:
5. What is meant by the term word equation?
6. Formulate a word equation to represent your observation in (3).
7. What is meant by:
   (a) Additional Sign on the left hand side of an equation.
   (b) . Additional Sign on the right hand side of an equation.
   (c) Arrow between the product and the reactants.
8. Explain the importance of word equation in Chemistry?
9. Write the word equation for the following processes which occur in our Daily life.

(a) photosynthesis (b) respiration (c) burning of charcoal

6. Identify the reactants and products in the above processes.
   A word equation is an expression of a chemical reaction or mathematical equation using words rather than letters, numbers, and operators. In chemistry,
   a word equation indicates the order of events of a chemical reaction.

The number of moles and types of reactants yield the number of moles and types of products. Word equations will help in learning chemistry because they reinforce the thought process involved in writing a chemical reaction or equation.

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For example:
When metals react with water, metal hydroxides and hydrogen gas are formed.
This can be represented in different ways as shown below:
When metals react with acids, a salt of the metal and hydrogen gas are formed.

The salt of the metal is named following the rules.
Calcium + Water Calcium and hydroxide + Hydrogen
When metals react with oxygen, metal oxides are formed.
Magnesium + Oxygen = Magnesium oxide
When metals react with oxygen, metal oxides are formed.
Zinc + Oxygen = Zinc oxide

1.2: Reactivity Series of Metals
Metals are a reactive group of elements. This means they have a high tendency to form compounds with other elements. They react with air , water, and acids under certain conditions.

Activity 1.2: Discovering the reactivity series
What you need: notebooks, stylus, slate,perkins brailler and braille papers.
What to do:
Read/ listen to the poem below and answer the questions that follow:
First comes potassium
At the top
Next comes sodium
Which goes pop Calcium is third

And good for bones, Magnesium is fourth,
There’s more! You moan.
Aluminium is fifth And used is cans,
Zinc comes sixth Used to coat cars and vans.
Iron is seventh And found in steel.
Eighth is lead Which can make you ill.
Next is copper Used in chimes Tenth is silver I
Which makes nothing that rhymes
Lastly there’s gold
Which makes bracelets and rings
Metals are useful and do lots of things!

Questions:

1. List the metals in the poem.
2. Outline the uses of each metal in our daily life.
3. Arrange the elements you have listed in ascending order according to their order of reactivity.
   Using the Internet / textbooks, research on how each metal reacts with air.
   Arrange the metals according to their reactivity, starting with the most
   competitive metal for oxygen.
   Present your findings to the rest of the class.

1.3: Comparing Reactivity of Metals
The reactivity of different metals can be compared by experimentation. This involves selecting and reacting metals with common reagents under the same conditions.
Then determine which one reacts faster than the other. From observations like rate of gas bubbling and other changes, metals can be ranked to form a reactivity series.

Reactions of metals with air
Activity 1.3: Discovering how metals compete for oxygen
What you need: Piece of magnesium, calcium, Iron, notebooks, stylus, slate, Perkins brailler and braille papers.
What to do:
Your teacher will perform a demonstration in which magnesium, calcium and iron burn in air. Watch and listen attentively during the demonstration.
Questions: Form small groups and discuss how metals compete for oxygen. Use the following guiding questions:

a) When a substance burns in air, the reaction is called a combustion reaction.
When a substance combusts in air, is it really reacting with oxygen?
b) Describe the observations when the following metals are burned in oxygen or air: magnesium, calcium and iron.
c) Arrange the metals in (b) in ascending order according to their reactivity.

Reactions of metals with water
Activity 1.4: Investigating how cold water reacts with metals
What you need: Glass trough, small pieces of sodium and calcium metal, notebooks, stylus, slate, perkins brailler and braille papers. Animation or simulation showing how sodium and calcium react with metals.
Caution : Sodium is a very reactive metal, therefore, handle with care.

2.Reaction of sodium with cold water
3.Record what you have observed or heard.
4.Describe the effect of resultant solution on blue and red litmus paper.
5.Write the word equation for the reaction.
6.Repeat steps (1 )-(4) using Calcium.

Magnesium reacts with water slower compared to the reaction between Calcium with water. In activity 1.4, you shall investigate the reaction of some weak metals with steam.

Activity 1.5: Investigating reaction of steam with Magnesium and Zinc metal
What you need: Wet sand, magnesium ribbon, zinc powder, source of heat, delivery tube, water trough, wooden splint, and water. A video clip showing how
magnesium and zinc react with cold water, notebooks, stylus, slate, perkins brailler and braille papers.
What to do

1. Watch an animation showing how magnesium and zinc react with cold water.
   As the teacher interprets in sign language.

2. What have you observed or heard?
3. What is the effect of the gas produced on burning splint?.
4. Write the word equation for the reaction that took place.
5. Which other metal can be used in this activity a part from zinc and magnesium.

Generally, metals react with water according to their position in the reactivity series.
Very reactive metals like sodium and potassium react vigorously with cold water to produce metal hydroxide and hydrogen gas. Less reactive metals like iron and zinc do not react with cold water. They react with steam to produce a metal oxide and hydrogen.

Reactions of metals with dilute acids

Activity 1.6: Comparing reactivity of some metals with dilute hydrochloric acid
What you need: metals (calcium, copper, iron, magnesium, zinc), dilute hydrochloric acid and zinc, notebooks,stylus, slate, serkins brailler and braille papers.
What to do
1.Plan and design an investigation to compare the reactivity of the metals when they react with dilute hydrochloric acid.
2.Discuss and measure level of reactivity of these metals with dilute hydrochloric acid.
3.Arrange the metals in order of reactivity, beginning with the most reactive metal.
4. Carryout the investigation according to your plan design.
5. Write a report showing the following steps clearly:
a) Aim of the investigation.
b) Steps followed in their correct orders
c) Cautions or precautionary measures
d) How does reactivity of the metal determine its position in the reactivity series
6. Identify the metals that reacted with dilute hydrochloric acid.
7. State what was observed and write word equations for the reactions.
8. Identify the metals that did not react with the acid.
9. Share your report with the rest of the class.

1.4: Alloys
A mixture of metals has better properties than single metals. An alloy is a mixture of two or more metals or a metal and a non-metal. Perform task in Activity 1.7 to discover the composition of an alloy.

Composition of Alloys
Activity 1.7: Discovering the composition of alloys
What you need: notebooks, stylus, slate, perkins brailler and braille papers.
One stick and a bundle of sticks.
What to do

1. Try breaking one stick with your hands. What happens?
2. Tie a bundle of sticks together and try to break them with your hands. What have you observed?

Properties of Alloys
Pure metals have desirable properties like electrical conductance, hardness among others. These properties of metals can be improved by forming alloys. In activity 1.8, you will discover the properties of alloys.
Activity 1.8: Investigating properties of alloys
What you need: Sheet of steel, iron, brass, solder, hammer, metallic ruler’ notebooks, stylus, slate, and perkins brailler and braille papers.
What to do
Tabulate all your results in an appropriate table.
1). Take the steel and iron. Observe/feel their surfaces. Note it as shiny or non-shiny, smooth or rough.
2). Hammer the iron sheet on a hard surface. Do the same to steel. What is observed? What does this tell you about alloys and metals?
3). Repeat procedure (1) and (2) using other alloys.
4). Write or braille your answer.

Uses of Alloys
Alloys have different properties depending on their composition. The use of metals depends on the properties of metals contained in the alloys. Figure 1.5 Show some uses of alloys. How are the items in Figure 1.5 important to you?