Reactivity of Metals and Non-metals by Lizelle Swanepoel

PRIOR KNOWLEDGE:

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1. Element:
A substance which cannot be broken down into simpler substances by
chemical means.

2. Compound:
A substance containing 2 or more different elements chemically
bonded together.

3. Molecule:
Two or more atoms chemically bonded together in a fixed ratio

4. CO₂ test:
CO₂turns clear lime water milky.

5. Acid / base indicators:
Litmus - goes red in an acid and blue in base.

6. Endothermic reactions:
More energy absorbed for the reaction than released.

7. Exothermic reactions:
More energy released than absorbed.

8. Particle diagrams

CHEMICAL REACTIONS TO ILLUSTRATE REACTIVITY OF ELEMENTS:

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A chemical reaction is:
A process that involves the rearrangement of the structure of a substance, where existing bonds in the compound break and new bonds form.

Let's look at some reactions:

a) Reacting carbon with oxygen.

In this experiment you will receive a boiling tube which has been filled with oxygen.
Heat a small amount of carbon powder on the Bunsen using the deflagrating spoon.
When the carbon glows red hot place it into the boiling tube containing oxygen.

Observation: ______________________________________________________

b) Reacting magnesium ribbon with carbon dioxide:

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• Combust C-powder with O₂, remove the deflagrating spoon and stopper the gas jar.
• Connect a small piece (3cm) of Mg onto deflagrating spoon and ignite it in the Bunsen.
• Insert the burning magnesium into the carbon dioxide. (Avoid touching gas jar with burning Mg.

Observation: _______________

Word equation:

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carbon + oxygen→ carbon dioxide

Chemical equation:

_________ + ___________ → ___________

An investigation of the reaction between magnesium and copper oxide

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Thoroughly mix small amounts of magnesium powder and copper oxide powder.
Place the mixture on a bottle top.
Place the bottle top on a pipe-clay triangle resting on a tri-pod.
Place a medium Bunsen flame below the bottle top and stand back.

Post-burning procedure - BURNING MAGNESIUM IN COPPER OXIDE:

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Place the products of the reaction in a small beaker.
Add dilute hydrochloric acid to the beaker and heat gently to dissolve magnesium oxide and any unused magnesium.
Filter or decant the contents of the beaker.

Observations:
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

Conclusion:
_________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

Word Equation:
_________________________________________________________________________ _________________________________________________________________________

Chemical Equation:
_________________________________________________________________________ _________________________________________________________________________

Particle Diagrams of reactants and products:

THE REACTIVITY SERIES:

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Metals (and non-metals) can be arranged in a reactivity series based on the reactions of the metals and their compounds.
The reactivity series lists elements (mostly metals) in order of decreasing reactivity.
Understanding the reactivity series is fundamental to chemistry.

This is the order of METALS in decreasing reactivity, below:

Reactivity Song

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Reactivity series in Order

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You need to MEMORIZE THIS

Why are H and C on the Reactivity Series of Metals??

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The only non-metals in the reactivity series are Carbon (C) and Hydrogen (H).

The reason for these two elements being included is? _________________________________________________________________________ _________________________________________________________________________

REACTIVITY OF METALS

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A COMPARISON - using Group 1 metals (alkali metals).

REACTIVITY - What is it?

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Reactivity is a molecule or compound's relative capacity to undergo a chemical reaction with another molecule or compound.

Reactivity of metal groups decrease from left to right on Periodic stable.
Reactivity of non-metals decrease from right to left on Periodic Table.
Group 8 Nobel Gases don't react. They are UNREACTIVE (INERT).

CONCLUSION:

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FOR METALS - REACTIVITY INCREASES DOWN A GROUP.

Cs is the most reactive alkali metal.
Rb is the 2nd most reactive metal in Group 1.
K is the 3rd most reactive.
Na is the 4th most reactive in the group.
Li is the least reactive in the group (Gr 1).

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REACTIVITY OF THE NON-METALS

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A COMPARISON - using Group 7 non-metals (Halogens)

CONCLUSION:

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FOR NONMETALS - REACTIVITY DECREASES DOWN A GROUP.

F is the most reactive in Group 7.
Cl is the 2nd most reactive non-metal in Group 7.
Br is the 3rd most reactive.
I is the least reactive halogen.

Displacement Reactions

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A displacement reaction, is a reaction in which one element is substituted for another element in a compound.

For single displacement reactions the starting materials are always pure elements, such as a pure zinc metal or hydrogen gas, plus an aqueous compound.
When a replacement reaction occurs, a new aqueous compound and a different pure element will be generated as products.
The general pattern of a single replacement reaction is shown below.

AB(aq) + C → A + CB(aq) Where A and C are pure elements.

We can see that A is replaced by C, in compound AB to make a new compound CB.
Another thing you might notice is that A starts out as an ion in solution but appears in its elemental form on the product side.
The reactant C does the opposite: it starts out in its elemental form on the reactant side, but it ends up as an ion in aqueous solution as part of the compound CD.

Predicting if a single replacement reaction will occur

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Once we know which elements might get swapped in our single displacement reaction, we can predict whether the reaction will occur based on knowledge of the relative reactivities of the two elements.

If element C is more reactive than element A, then C will replace A in a compound.
If element C is less reactive than element A, then there will be no reaction.

Displacement of Metals from Solutions

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Displacement reactions are easily seen when a salt of the less reactive metal is in the solution. During the reaction:
• the more reactive metal gradually disappears as it forms a solution
• the less reactive metal coats the surface of the more reactive metal

Magnesium is more reactive than copper

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When a piece of magnesium is dipped into blue copper sulfate solution:
• the blue colour fades as colourless magnesium sulfate solution forms
• brown copper coats the surface of the magnesium

EXPERIMENT

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You can investigate the reactivity of metals using displacement reactions. Complete the table showing the results from a series of experiments involving four metals and solutions of their salts. Please indicate a tick showing where there is a visible reaction and a cross showing where there is no visible reaction. If you place a tick, the please provide an observation.

Observations:______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Displacement of Metals from Metal Oxides.

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Remember the reaction you did with Magnesium and copper oxide?
Does this reaction make more sense now knowing the reactivity series?

A metal will reduce (take oxygen) from the oxide of any metal below in the reactivity series. When the magnesium was heated with the copper oxide, there was a very vigorous reaction with a lot of heat and light given off (highly exothermic).

Mg (s) + CuO(s) MgO (s) + Cu

The magnesium readily gives up it electrons to the copper (II) ions in the copper oxide, as it gives up its electrons more easily than the copper.

This type of reaction is known as THERMITE REACTION.

THERMITE DEMO:

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The thermite reaction of aluminium (Al) powder with powdered iron oxide (Fe2O3) is used to produce molten iron to weld railway lines together. Your teacher should do this demo with you in a controlled environment.

HOMEWORK QUESTIONS:

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1) Why would molten iron be produced?
2) Write a word equation for the reaction above?
3) Draw a particle diagram for the reaction.
4) Write a balanced chemical equation for the reaction.

Reactions of Metal Oxides and Hydrogen

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Hydrogen can remove oxygen from metallic oxides, producing the metal and water.

E.g. Hydrogen is passed over hot lead (II) oxide to produce lead metal and water.

NOTE:

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Hydrogen can reduce many other metallic oxides.
However, this reaction becomes more difficult the more reactive the metal is.
Hydrogen cannot remove oxygen from oxides of very reactive metals such as sodium and calcium.

Revision Questions

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1. When magnesium powder is heated with copper oxide (CuO) powder, on a spatula, a reaction is observed, and a white powder is formed;
a. Draw a labelled diagram to show the apparatus used to perform this experiment.
b. Describe a suitable CONTROL to ensure that the results of this experiment are reliable.
c. Draw particle diagrams for this reaction.

2. A solution of copper sulphate is reacted with a piece of aluminium metal.
a. Describe the observations that you would expect for this reaction.
b. Write a word equation for the reaction which occurs.
c. Suggest a solution with which you would NOT expect any reaction with a piece of aluminium.

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3. A small piece of potassium metal is dropped into a basin of water.
a. What would you observe?
b. Name the gas given off and describe a test to identify the gas
c. Write down TWO word equations (including phases) :
one for the reaction between potassium and water, and
one for the reaction which takes place when testing for the gas.

4. Complete the following word equations: [ state ‘NO REACTION’ where applicable]
a. Magnesium + steam
b. Carbon + magnesium oxide
c. Iron + zinc oxide
d. Lead + copper oxide
e. Magnesium + silver sulphate f. Lead + zinc nitrate

5. Zinc powder is added to a solution of copper sulphate
a. write the word equation for the reaction which takes place
b. List 3 observations that can be made during this reaction

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6. The reaction between aluminium and iron oxide is used to join lengths of railway track.
It is called the THERMIT REACTION:
Fe₂O₃(s) + 2 Al(s) --> Al₂O₃(s) + 2 Fe(l)
a. Why does aluminium react with iron oxide?
b. What does (l) after the Fe in the equation mean?
c. Suggest why the thermit reaction can be used to join lengths of railway track.

7. Metal X displaces metal Y AND Z from solutions of their compounds. Metal Z displaces metal Y from solutions of its compounds, but not metal X from solutions of its compounds. Place X, Y and Z in order of reactivity.

8. Carbon will reduce lead (II) oxide to lead and zinc oxide to zinc. a. Write the chemical equations for the two reactions. b. Which of the two oxides is reduced more easily? Give a reason.

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Oxidation Reduction (Redox) Reactions
An oxidation reduction (redox) reaction happens when electrons are transferred between atoms.
A loss of electrons is called oxidation, and we say that atom has become oxidized.
A gain of electrons is called reduction, and we say that the atoms has become reduced.
The two separate parts (oxidation and reduction) of an oxidation reduction (redox) reaction are called half reactions. Two half reactions can be put together to make the whole reaction.
Oxidation numbers are numbers that can be written above atoms to show whether they are gaining or losing electrons.

lizellexs — 2020-07-26 18:57:57 UTC

lizellexs — 2020-07-26 18:59:00 UTC

NOBLE GASES DON’T REACT

lizellexs — 2026-04-11 21:03:53 UTC