Indigestion

Your stomach produces hydrochloric acid to:
-Kill Bacteria
-Digest food


If there is bacteria on your food it is broken down by digestive enzymes which need acidic conditions in order to work properly.

If there is too much hydrochloric acid in the stomach it can cause indigestion pain.

Sometimes the acid can escape from the top of the stomach causing pain in the tube leading to the mouth. This is known as heartburn though it has nothing to do with the heart.

Medicines called antacids are able to get rid of excess stomach acids. They contain bases - substances that react with acids.

The neutralisation reaction between an acids and a base produces water and salt. Some bases are soluble and a base dissolved in water is called an alkali.

Acid + Base -----> Salt + Water

Acids and alkalis can be described using the PH scale.

A  neutral liquid (e.g. water) has a PH of 7.

You can find out whether a liquid is an acid or alkali using a indicator.

Litmus paper is an indicator

Blue litmus paper turns red under acid conditions and red litmus paper turns blue under alkaline conditions but the paper must be damp to work.

Key Words:

Digested

Antacids

Bases

Salt

Acid

Alkali

PH Scale

Indicator

Litmus Paper

Questions:

1) What causes indigestion?

2) What is an antacid?

3) Stomach acid would turn universal indicator orange, what is its PH? (hint: use the PH scale)

What you should know:

• 3.1 Know that hydrochloric acid is produced in the stomach to:
  • a) help digestion
  • b) kill bacteria
• 3.2 Be able to describe indigestion remedies as containing substances that neutralise excess stomach acid.

Reactions of Calcium Compounds

Making Limewater-

Limestone is a raw material used in manufacture of concrete, which, when heated, calcium carbonate it contains forms calcium oxide.

Calcium Carbonate ----> Calcium Oxide + Carbon Dioxide

CaCO³(s) ------> CaO(s) + CO²(g)

When water is added to calcium oxide a lot of heat is released and calcium hydroxide, a crumbly white solid, forms in the reaction.

Calcium Oxide + Water -----> Calcium Hydroxide

CaO(s) + H²O(l) ------> Ca(OH)²(s)

Calcium Hydroxide dissolves when more water is added forming a solution, commonly known as limewater.

A Test For Carbon Dioxide-

Limewater turns milky in the presence of Carbon Dioxide because white insoluble calcium carbonate forms:

Calcium Hydroxide + Carbon Dioxide -----> Calcium Carbonate + Water

Ca(OH)²(aq) + CO²(g) ------> CaCO³(s) + H²O(l)

Neautralising Acids With Limestone-

*Acids are neutralised by alkalis, called a neutralisation reaction. 

*Calcium Carbonate, Calcium Oxide and Calcium Hydroxide can neutralise acids.

*If, for example, farmers need to reduce the acidity of their soil, they could spray any of the powdered chemicals mentioned over their fields.

*Coal naturally contains sulfur and compounds.

*When coal burns the sulfur forms sulfur dioxide.

Sulfur + Oxygen -----> Sulfur Dioxide

S(s) + O²(g) ------> SO²(g)

Key Words:

Limewater

Neutralisation Reactions

Questions:

1) What is the test for carbon dioxide?

2) Which calcium compounds can be used to reduce soil acidity?

3) How do they reduce acidity?

What you should know:

• 2.14 Be able to describe the effect of water on calcium oxide to form calcium hydroxide ('slaked lime')
• 2.15 Be able to describe how calcium hydroxide dissolves in water to form a solution, known as limewater.
• 2.17 Be able to explain how calcium oxide, calcium hydroxide and calcium carbonate can be used to neutralise soil acidity.
• 2.18 Be able to explain how calcium carbonate can be used to remove acidic gases from coal-fired power station chimneys, reducing harmful emissions and helping to reduce acid rain.

Chemical Reactions

In general:

Reactants ---------> Products

For example:

For the thermal decomposition of zinc carbonate, the reactant is zinc carbonate and the products are zinc oxide and carbon dioxide.

The word equation is:

Zinc Carbonate -----> Zinc Oxide + Carbon Dioxide

*Substances are made up of atoms which are the smallest part of an element that can take part in chemical reactions. 

* A compound consists of atoms of two or more different elements chemically joined.

The chemical formula of a compound shows symbols of the element it contains and ratios in which the atoms *are present

Balanced equations shows what happens to atoms in a chemical reaction:

Zinc Carbonate -----> Zinc Oxide + Carbon Dioxide

ZnCO³(s) --------> ZnO(s) + CO²(g)

*There are the same numbers of atoms of each element on both sides, so it's a balanced equation.

*(s) and (g) are state symbols showing what is a solid and a gas. 

*Liquids are shown by (l) and aqueous solutions shown by (aq).

Atoms aren't made or destroyed in a chemical reaction but rearranged meaning the total mass stays the same before and after the reaction.

Precipitation reactions happen when soluble substances react together to form a insoluble product, namely the precipitate. 

Silver Nitrate and Potassium Bromide react together to form insoluble silver bromide.

Silver Nitrate + Potassium Bromide ------> Potassium Nitrate + Silver Bromide

AgNO³(aq) + KBr(aq) ------> KNO³(aq) + AgBr(s)

Key Words:

Reactant

Products

Atom

Element

Compound

Chemical Formula

State Symbols

Precipitation Reactions

Soluble

Insoluble

Precipitate

Questions:

1) What is an atom?

2) What does the ³ in a formula tell you?

3) How do precipitation reactions occur?

What you should know:

• 2.12 Be able to describe the ease of thermal decomposition of different metal carbonates.
• 2.13 You should understand that:
  • a) atoms are the smallest particles of an element that can take part in chemical reactions
  • b) during chemical reactions, atoms are neither created nor destroyed
  • c) during chemical reactions, atoms are rearranged to make new products with different properties from the reactants 
  • 2.16 You should know and understand that the total mass before and after a reaction in a sealed container is unchanged, as shown practically by a precipitation reaction (known as the 'Law of Conservation of Mass').

Thermal Decomposition of Carbonates PCA (Experiment)

Calcium Carbonate decomposes when it is heated, producing calcium oxide and carbon dioxide. Carbon dioxide can be detected using limewater. When carbon dioxide is passed through it the limewater turns milky.

Experiment:
Do all metal carbonates break down in the same way?

Hypothesis;
Some metal carbonates decompose more easily then other when they are heated.

Apparatus:

Eye Protection
Test tubes (2 per carbonate)
Right angled delivery tube
Spatula
Bunsen burner
Clamp stand

Chemicals:
Limewater
Copper Carbonate
Lead Carbonate
Zinc Carbonate
Calcium Carbonate
Magnesium Carbonate


Health and Safety:
-Eye protection must be worn
-It's important not to inhale any substances
-Wash hands after use of chemicals
-Essential for delivery tube to be removed from limewater before removal of bunsen burner


Method:

1. Set up all equipment
2. Measure out 1g of chosen carbonate to be tested
3. Fix delivery tube onto test tube containing carbonate
4. Measure out limewater and clamp boiling tube onto stand
5. 5. Clamp test tube containing carbonate above the bunsen burner
6. Heat metal carbonate (time this) being cautious not to let the carbonate rise. Once limewater is milky record observations
7. Remove limewater and take the bung off the metal carbonate BEFORE you turn off the bunsen burner

Observations can be recorded in a table similar to the one below:

What you should know:

• 2.11 Revise the investigation on the ease of thermal decomposition of carbonates, including calcium carbonate, zinc carbonate and copper carbonate.

Limestone and its Uses

Limestone is a sedimentary rock made up of mainly calcium carbonate. 
It’s cheap and easy to obtain.
Some uses:
1) Building materials – limestone can be quarried and cut into blocks to be used in building.However, it is badly affected by acid rain.
2) Glass making – glass is made by mixing limestone with sand and sodium carbonate: 
Limestone + sand + sodium carbonate ----> glass
3) Cement making – limestone can be “roasted” in a rotary kiln to produce dry cement. It’s then mixed with sand and gravel to make concrete

If soil is too acidic crops will fail. Limestone can also be used as a neutralising agent. 
There are two reactions to know:
1) Firstly, a THERMAL decomposition reaction is used to break the calcium carbonate down into calcium oxide (quicklime) and carbon dioxide: 
Calcium Carbonate ----heat> calcium oxide + carbon dioxide
2) This is then “slaked” with water to produce calcium hydroxide (“slaked lime”): 
Calcium Oxide ----water> calcium hydroxide 
Calcium hydroxide is alkaline and is used to neutralise acidic soil.

Key Words:

Quarry

Thermal Decomposition

Cement

Concrete

Questions:

1) What's the word equation for the thermal decomposition of calcium carbonate?

2) How is cement made?

What you should know:

• 2.8 Have an understanding of the balance between the demand for limestone and the economic, environmental and social effects of quarrying it.
• 2.9 Have an understanding of the commercial need for quarrying calcium carbonate on a large scale, as a raw material, for the formation of glass, cement and concrete.
• 2.10 Be able to describe the thermal decomposition of calcium carbonate into calcium oxide and carbon dioxide.

Rocks and their Formation

Rocks and their Formation:

Igneous Rocks

Rocks deep inside the Earth may become hot enough to partially melt. Molten rock is called magma. It may stay inside the Earth, or it may erupt onto the surface as lava. When molten rock cools down it solidifies and becomes solid rock. Rocks formed this way are called IGNEOUS ROCKS

There crystals interlock.

The size of the crystals depends on the rate at which the magma or lava cools. E.g.Granite

Sedimentary Rocks

Rock that has formed through the deposition and solidification of sediment.
Examples: sediment transported by water (rivers, lakes, and oceans), ice ( glaciers), and wind.
Sedimentary rocks are often deposited in layers, and contain fossils

Metamorphic Rocks

The action of heat and/or pressure can change rocks, causing new crystals to form. These changed rocks are called Metamorphic Rocks.

Example: Marble is a metamorphic rock formed from chalk or limestone. The grains in chalk and limestone are weakly joined together with small gaps between them. When marble forms, the grains become new crystals of Calcium Carbonate that interlock tightly.

Erosion

Sedimentary rocks are more likely to erode than igneous and metamorphic rocks. This is because metamorphic and igneous rocks have interlocking crystals

Key words:

Magma
Lava
Solidifies
Igneous Rocks
Crystals
Granite
Erosion
Sediment
Fossil
Metamorphic
Marble


Questions:

1. Name an example of a igneous rock.
2. Why are fossils often found in sedimentary rocks not igneous?
3. What is erosion?


What you should know:

• 2.1 Be able to Be able to describe that igneous rocks, such as granite, are:
  • a) formed by the solidification of magma or lava
  • b) made of crystals whose size depends on the rate of cooling
• 2.2 Be able to describe chalk and limestone as examples of sedimentary rocks.
• 2.3 Be able to describe how sedimentary rocks are formed by the compaction of layers of sediment over a very long time period.
• 2.4 Know and understand that sedimentary rocks:
  • a) may contain fossils
  • b) are susceptible to erosion
• 2.5 Be able to describe marble as an example of a metamorphic rock.
• 2.6 Be able to describe the formation of metamorphic rocks by the action of heat and/or pressure, including the formation of marble from chalk or limestone.
• 2.7 Know and understand that limestone, chalk and marble exist in the Earth’s crust and that they are all natural forms of calcium carbonate.

The Atmosphere Today

The Atmosphere Today:

Gases in the Earth's atmosphere today :

Nitrogen - 78%
Oxygen - 21%
Argon - 0.9%
Carbon Dioxide - 0.04%
other gases - traces
[there is also water vapour but that changes too much from day to day so it is not included]

Some of the other 1% gases are unreactive noble gases, mainly argon. A small amount of CO2 is found aswell (0.04%). There are also trace amounts of other gases such as Carbon Monoxide, Methane, Nitrogen Oxides, Sulfur Dioxide.

The amounts of gases in the atmosphere may vary. For example -natural causes: volcanoes can release alot of sulfur dioxide and lightning can produce nitrogen oxides.

Human activity can also change the amount of certain gases in the atmosphere. 

• Deforestation means fewer trees to remove carbon dioxide from the atmosphere by photosynthesis
• Burning fossil fuels increases the amount of carbon dioxide, carbon monoxide and sulfur dioxide in the atmosphere
• Engines and furnaces can release nitrogen oxide
• Cattle and rice fields release large quantities of methane

Nitrogen is the main gas in the atmosphere today. There are different theories to where it came from

1) Volcanoes released nitrogen when the earth was young which means the atmosphere has always contained a lot of nitrogen

2) Nitrogen was added to the atmosphere gradually due to the reactions of nitrogen-containing compounds released from volcanoes.

Key Words:

Noble Gases

Trace

Deforestation

Questions:

1.Give two examples of human activity that could increase the amount of carbon dioxide in the atmosphere

2. List the thee main gases in the air, order of abundance

3. How does deforestation increase the amount of carbon dioxide in the air?

What you should know:

• 1.8 Be able to describe the current composition of the atmosphere and interpret data sources showing this information.
• 1.9 Be able to demonstrate an understanding of how small changes in the atmosphere occur through:
  • a) volcanic activity
  • b) human activity, including the burning of fossil fuels, farming and deforestation

Oxygen in the Atmosphere PCA

Oxygen in the Atmosphere PCA:

Oxygen is essential for humans.

Many substances , including metals, react with the oxygen in the air. Some react quickly and some slowly.

E.g / When Iron rusts it uses up oxygen in the air. Reactions like these can be used to find out the percentage of oxygen in the air.

Experiment:

How much air is used when metal reacts with it?

Hypothesis - 

About one fifth of the volume of air is oxygen

Apparatus and Chemicals - 

• Test Tube
• Beaker (100cm3)
• Ruler
• Iron Wool

Method - 

1 Put about 3 cm depth of iron wool into the test tube and wet it with water. Tip away excess water.

2 Put about 20 cm³ water into the beaker. Invert the test tube and place it in the beaker of water (see diagram). Measure the length of the column of air with the ruler.

3 Leave for at least a week.

4 Measure the new length of the column of air, taking care not to lift the test tube out of the water.

Rusting is an oxidation reaction of iron with oxygen.

iron + oxygen → iron oxide

What you should know:

1.7. Investigate the proportion of oxygen in the atmosphere

A Changing Atmosphere

A Changing Atmosphere:


As the earth cooled down, water vapour in the air condensed to form the oceans. Carbon Dioxide in the atmosphere then dissolved into the oceans. Scientists believe half of the world's carbon dioxide was lost through this way

Some marine organisms use dissolved carbon dioxide to make shells of calcium carbonate and as the creatures die their shells fall and become sediment. Over millions of years the layers of sediment compact to form sedimentary rock. 

Limestone is mostly calcium carbonate.

Scientists believe life started 4 billion years ago. About 1 billion years ago, some organisms developed the ability to photosynthesise.

Photosynthesis is taking in carbon dioxide, releasing oxygen.

Over time, more photosynthesising organisms evolved. Increasing levels of photosynthesis sped up the rate at which Carbon Dioxide was removed from the atmosphere and the rate oxygen was added to th atmosphere.

Key Words:

Sedimentary Rock

Limestone

Photosynthesise

Questions:

1. What is the main substance in limestone?

2. What are two ways carbon dioxide was removed from the early atmosphere?

3. Explain how the amount of oxygen in the atmosphere gradually increased?

What you should know:

• 1.5 Be able to describe how the amount of carbon dioxide in the atmosphere was reduced by:
  • a) the dissolution (dissolving) of carbon dioxide into the oceans
  • b) the later incorporation of this dissolved carbon dioxide into marine organisms which eventually formed carbonate rocks
• 1.6 Be able to explain how the growth of primitive plants used carbon dioxide and released oxygen by photosynthesis and consequently the amount of oxygen in the atmosphere gradually increased

The Early Atmosphere

The Early Atmosphere:

By studying other planets and moons scientists hope to find out more about the Earth's early atmosphere. They think evolution of life on Earth caused its atmosphere to change

Scientists are particularly interested in volcanoes because they release large amount of gases. Volcanoes, nowadays, mainly release Carbon Dioxide and Water Vapour.

So scientists believe these gases were in the earth's early atmosphere.

The atmosphere of Titan is 98% nitrogen , which some think were released by volcanoes. They think that this could have been similar to the world's early atmosphere.

 There are also volcanoes on Mars and Venus ( their atmosphere is mainly carbon dioxide). This make's some scientists believe the earths early atmosphere was that of Carbon Dioxide

However , Titan has a icy interior. Whilst Earth , Mars and Venus have a rocky interior; This makes it more likely the earth's early atmosphere was similar to that of Mars and Venus.

There was little or no oxygen in the early atmosphere. (volcanoes do not produce oxygen and the earth's oldest rocks would only form in the absence of oxygen)

As the earth became older , it cooled down. The water vapour in the hot atmosphere also cooled down and condensed into liquid water which formed the oceans.

Key Words:

Atmosphere

Questions:

1. Name the gases thought to have been in the Earth's early atmosphere and the evidence to support this

2. How is Titan's atmosphere different to that of Mars and Venus today?

3. Why haven't the atmosphere on Mars and Venus changed for billions of years, but Earth's atmosphere has?

What you should know:

• 1.1 Know that the gases produced by volcanic activity formed the Earth’s early atmosphere.
• 1.2 Know that the early atmosphere contained:
  • a) little or no oxygen
  • b) a large amount of carbon dioxide
  • c) water vapour and small amounts of other gases.
• 1.3 Know why there are different sources of information about the development of the atmosphere which makes it difficult to be precise about the evolution of the atmosphere.
• 1.4 Be able to describe how condensation of water vapour formed oceans.

Welcome

Hi,
This is a blog for all of you that need help revising for Edexcel Chemistry GCSE.

This particular blog is just for C1- Chemistry in Our World but in future I will try and create both a blog for C2 and C3. 

There are pages on the right, for each topic, where I'll link each completed post to. This will make it easier to find whatever you need help on.

Hope this helps all of you and you're all able to do well in any upcoming exams. 

Shakira