Rusting and Other Forms of Iron Corrosion

Reactions of Metals

Metals have three common corrosion reactions:

1. metal + oxygen --> metal oxide
2. metal + water --> metal hydroxide + hydrogen gas
3. metal + acid --> metal salt + hydrogen gas

We will then use the results of our investigation (of the reactions of Pb, Mg, Ca and Al) to create an Activity Series.

Collision Theory

Why do some reactions happen quickly? Why do some chemicals not react at all when mixed together?

Here is a site that has some good practice for balancing equations


http://education.jlab.org/elementbalancing/

Balancing Equations

STEP ONE

Identify the type of reaction, so identify the products.

e.g. acid + base --> water + salt
e.g. acid + metal --> hydrogen + salt

STEP TWO

Work out the formula of the salt. Use "drop-and-swap",  but remember that this is just a method for finding the electrically-neutral ratio of ions.

STEP THREE

Balance the atoms using large numbers to change the quantity of each compound/molecule/atom.

Acids and Bases

Acids and Bases

an acid is a chemical compound that has extra hydrogen ions that it can loose. We found that when an acid is mixed with a base, a salt and water is produced. on the P.H. scale which is the standard way of measuring acids and bases the acids are between 0 and 6.9 and bases are from 7.1 to 14. so that means that 7 is neutral.

salts are a neutral compound which is not table salt excluding the first experiment.
these are the results we have for the tests we did:

• hydrochloric acid + sodium hydroxide = sodium chloride + water 

HCl + NaOH = NaCl +H2O

• hydrochloric acid + magnesium oxide = magnesium chloride + water

2HCl + MgO = MgCl2 + H2O

• nitric acid + sodium hydroxide = sodium nitrate + water

HNO3 + NaOH = NaNO3 + H2O

• nitric acid + magnesium oxide = magnesium nitrate + water

2HNO3 + MgO = Mg(NO3)2 + H2O

• sulfuric acid + sodium hydroxide = sodium sulfate + water

H2SO4 + NaOH = Na2SO4 +H2O this is not balanced

• sulfuric acid + magnesium oxide = magnesium sulfate + water

H2SO4 + MgO = MgSO4 + H2O

• ethanoic acid + sodium hydroxide = sodium ethanoate  + water

CH3COOH + NaOH = NaCH3COO + H2O

• ethanoic acid + magnesium oxide = magnesium ethanoate + water

2CH3COOH  + MgO = Mg(CH3COO)2 + H2O

• therefore
• acid + base = salt(not table salt) + water 

Acids and Bases

an acid is a chemical compound that has extra hydrogen ions that it can loose. We found that when an acid is mixed with a base, a salt and water is produced. on the P.H. scale which is the standard way of measuring acids and bases the acids are between 0 and 6.9 and bases are from 7.1 to 14. so that means that 7 is neutral.

salts are a neutral compound which is not table salt excluding the first experiment.
these are the results we have for the tests we did:

• hydrochloric acid + sodium hydroxide = sodium chloride + water 

HCl + NaOH = NaCl +H2O

• hydrochloric acid + magnesium oxide = magnesium chloride + water

2HCl + MgO = MgCl2 + H2O

• nitric acid + sodium hydroxide = sodium nitrate + water

HNO3 + NaOH = NaNO3 + H2O

• nitric acid + magnesium oxide = magnesium nitrate + water

2HNO3 + MgO = Mg(NO3)2 + H2O

• sulfuric acid + sodium hydroxide = sodium sulfate + water

H2SO4 + NaOH = Na2SO4 +H2O this is not balanced

• sulfuric acid + magnesium oxide = magnesium sulfate + water

H2SO4 + MgO = MgSO4 + H2O

• ethanoic acid + sodium hydroxide = sodium ethanoate  + water

CH3COOH + NaOH = NaCH3COO + H2O

• ethanoic acid + magnesium oxide = magnesium ethanoate + water

2CH3COOH  + MgO = Mg(CH3COO)2 + H2O

• therefore
• acid + base = salt(not table salt) + water 

GROUP SKUX: Repost of the indicator experiment

Sorry, the one that i uploaded was their fail one. This is the proper one.

Credit: Liam C-Grove, Ray MC

Acids & Carbonates

Acids and carbonates when they are mixed release carbon dioxide, water and salt.

Acid + Carbonate à Salt + Carbon Dioxide + Water 

Mixtures	Equations	Observations
Hydrochloric Acid + Copper Carbonate	2HCl + CuCO3 ---> CO2 + H2O + CuCl2	When the acid and carbonate mix together there is an immediate reaction as the mixture fizzes up it rises right to the top of the test tube and then suddenly starts to drop back down and goes back to a liquid, then about 20 seconds later it has started to change from an originally green cloudy colour to a clear light blue
Hydrochloric Acid + Magnesium Carbonate	2HCl + MgCO3 ---> CO2 + H2O + MgCl2	When the acid and carbonate mix together there is an immediate reaction as the mixture fizzes up it rises to about half way up the test tube and then suddenly starts to drop back down and goes back to a cloudy milky coloured liquid, unlike the copper carbonate solution this mixture doesn’t go back to a see-through clear liquid it remains cloudy with the milky colour.

Metal carbonates normally react with acid to form different types of salts, carbon dioxide and water. A metal carbonate is a type of metal that is made as a result of a mixture between carbon and oxygen. Hence the equation.

Acid + Carbonate ----> Salt + Water + Carbon Dioxide

GROUP SKUX (Ray MC, Liam C-Grove, Mady, J-Chan, T-Roar)

pH Scale & Indicators

pH Scale:

The pH scale is used to determine whether a substance is either acidic or basic. We want to find this information because it is important in determining if the substance can be applied to something. To find this out, you must add drops of Universal Indicator to the substance.
The pH scale has different colours and numbers to indicate this; the scale runs from 1 - 14.
However, the acids are from 1.0 - 6.9 (Pink - Yellow).


Litmus paper also helps to indicate acids and bases. The special paper turns either blue or red depending if it is an acid or a base. Blue for a base, red for an acid.

Credit: J-Chan

The reaction between acids and metals

when metals reacts with an acid they produce hydrogen and a salt e.g. sulfate, nitrate, chloride and ethanoate. in our experiments we used the same metal (magnesium) and reacted it with four different acids.
Facts:

• ·        Metal + acid = salt + hydrogen
• ·        Metals like copper and salt do not react with dilute acids
• ·        Reactive metals like lithium, sodium, potassium and calcium react violently with dilute acids
• ·        (H2) hydrogen is colourless and odourless. You may be able to hear a squeaky pop sound when a burning splint is held over a test tube which has hydrogen gas present.
• ·        Nitrate, chloride, ethanoate and sulfate are all types of salts

Reactions:

• ·        Ethanoic acid + magnesium strip = magnesium ethanoate + hydrogen

You know that a reaction has occurred due to violent fizzing, a release of heat, the substance becomes cloudy, the magnesium strip begins to corrode before disappearing, changes to an orange colour.

• ·        Sulphuric acid + magnesium strip = magnesium sulphate + hydrogen  

Reaction has occurred when magnesium is floating at the top of the substance, it begins to bubble and become cloudy, changes colour to a pink rather than red, magnesium strip may disappear

• ·        Hydrochloric acid + magnesium strip = magnesium chloride + hydrogen

Reaction has occurred when the substance begins to bubble and turn cloudy, magnesium floats to the surface before gradually disappearing, less violent than ethanoic reaction, the substance heats up as the hydrogen gas levels increase, changes colour to red

• ·        Nitric acid + magnesium strip = magnesium nitrate + hydrogen

Reaction has occurred when the substance begins to fizz and bubble, turns a red colour before going yellow, goes cloudy, mixture begins to warm, magnesium sinks to the bottom before disappearing

  Equations:

Mg_(s) + 2CH₃COOH_(aq) --> Mg(CH₃COO)_2(aq) + H_{2 (g)}
H2SO4 + Mg = MgSO4 + H2

2HCl + Mg = MgCl2 + H2

2HNO3 + Mg = Mg(NO3)2  + H2

       

Magnesium fizzing in hydrochloric acid

The final results of the reactions listed above

   

Acids used in the experiments above

Isotopes

Some elements have isotopes - atoms with different mass numbers, so different numbers of neutrons. For example, chlorine has a relative atomic mass of 35.45. This means that the average mass of all chlorine atoms is 35.45. From this we can infer that the most common isotope of chlorine has a mass of 35, but there must also be isotopes with a higher mass, such as 36 or 37.

Sodium Reaction Wed 3/6

If this doesn't work try the link here

http://www.youtube.com/watch?v=2T3Ll__C09w

Power and Friction Summary

Pressure

Pressure = Force/Area

Force must be measured in newtons (N).
Area must be measure in m².

Therefore, the unit for pressure is the N m^-2, or pascal (Pa).

In this lesson, we have to discuss how hydraulic brakes work in cars etc.

All of the scientists working hard

The tanker doesn't explode or crumple because the outside air pressure is balanced with the inside air pressure. The tanker crumples as the air is released out the it into another tanker because the air pressure inside the tanker has decreased this means that the pressure on the outside of the tanker is greater than the inside so the forces are no longer equal, this causes the outside pressure to push down on the tanker without a resisting force. As the pressure inside the tanker decreases the force being exerted per square meter on the outside of the tanker increases thus causing the tanker to crumple.

Power

Investigation Information

Sorry about ze late upload.

Work and Energy Transformation

In our investigation, we need to know about energy transformations happening in the swinging masses ("wrecking ball") and the work done (by friction) when the swinging mass hits the block ("building").

Gravitational Potential Energy

In our investigation, we found that we needed to know how to calculate the Gravitational Potential Energy of the swinging mass. Mr Nicoll gave a quick overview of how to do this, using a diver on a board as a context:

The key thing to note is that all units need to be converted to SI Units (kg for mass, m for height).

From this information, we could actually calculate the speed the diver hits the water at (assuming no energy was "lost" due to friction during the dive). This will be covered in tomorrow's lesson.

Wrecking Ball Inquiry

This week, we are investigating Energy, Energy Transformations and Work. We are investigating the collision between a swinging mass and a block. This should give us an idea about the forces involved when we change a variable about the swinging mass ("wrecking ball").

We have been given some guidelines for what needs to be achieved and when these should be achieved by:

Acceleration

Acceleration is derived from Δvelocity (in m s^-1) and Δtime (in s). This means we need to convert other units (km hr^-1 and min, for example) into SI units.

This is the same as:

a = Δv ÷ Δt

Δv = a × Δt

Δt = Δv ÷ a

On Graphs

On a d-t graph, acceleration looks like this:

Deceleration (negative acceleration) looks like this:

On a v-t graph, acceleration looks like B and D in the following graph. B is a higher rate of acceleration than D. Deceleration is represented by A (negative gradient). C is uniform motion (constant speed).

Calculating Acceleration from a Graph

To do this, you need a v-t graph. Acceleration is the gradient of the line on a v-t graph. This is the skill you are expected to be able to do to access Merit in NCEA. A v-t graph can also be used to calculate the distance covered (area under the line of the graph).

Alternatively, you use the tangent of the curved line for two points in a d-t graph (but this is very inaccurate). You then use this to find the initial and final velocity, and calculate acceleration from this. See Mr N if you really want to know how to do this!