Chemistry

Manufacture of Ammonia and Fertilisers

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Worldwide food production depends on the use of chemical fertilisers. Almost all of these contain nitrogen compounds, because although there is a huge amount of nitrogen in the air, it is not in a form that is suitable for most plants to use. At the beginning of the twentieth century, Fritz Haber and Carl Bosch perfected the Haber-Bosch process for the conversion of nitrogen and hydrogen into ammonia. This ammonia could be used to make nitric acid, and therefore chemical fertiliser. The Haber-Bosch process is based on a reversible reaction, so in this title we will learn about reversible reactions in general, and the principles of equilibria. Although chemical fertilisers have many advantages, there are some problems associated with them. In particular, excessive use of fertilisers can lead to eutrophication, which is where rivers become starved of oxygen.

The Earth and its Atmosphere

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

The Earth is believed to be about 4,500 million years old. Since its formation, there have been great changes both to the land the atmosphere. The early cooling caused the oceans to form and then, as life developed, the atmosphere of ammonia, carbon dioxide and methane became polluted by oxygen. The ozone layer developed and life became more complex. Eventually the atmosphere gained its current composition of around 78% nitrogen, 21% oxygen, 1% argon and small amounts of other gases such as carbon dioxide. On the land, the continents spread out from the original Pangaea super-continent. The three main rock types that exist on Earth are sedimentary, metamorphic and igneous. As life developed, carbon-chain compounds were created. Although originally associated with living things, 'organic' chemistry is now concerned with the whole range of compounds that contain chains of carbon atoms.

Extraction and Uses of Metals

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Metals are an important part of the history of humankind. The first stage in using a metal is to remove it from its ore, a metal-bearing mineral or rock. Most ores are oxides, so we need to find ways to remove oxygen from the metal oxide. This is called reduction. The most reactive metals are the hardest to extract, so sometimes a metal might be expensive, even though it is not particularly rare. Aluminium and iron are two important metals. We will learn about how they are extracted from their ores. Almost all iron is converted into steel. We will consider how various metals, metal alloys and metal compounds are useful to us. The title will also look at how metal extraction can cause environmental problems and how the recycling of metals can help to reduce this.

Foods, Medicines and Emulsions

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Chemistry can help us to understand some of the issues concerning food and medicine. For example, fermentation is a chemical process that uses the enzymes from yeast. Sugars are converted to alcohol and carbon dioxide. This reaction is used to make alcoholic drinks and bread rise. Through history, humankind has found remedies for illnesses. Willow is useful for relieving pain. Originally, this was used in the form of a soup. Later, other painkilling drugs were discovered. Science has also helped us to understand traditional methods of making foods such as cheese and yoghurt. There is a huge industry associated with making food attractive to eat, and this title will consider this. We will also learn that preservatives can give food a longer shelf-life. The special food needs of babies and slimmers can also be addressed by chemistry.

Products from Crude Oil

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

The substances in crude oil are called 'fossil fuels', but they can also lead to a range of chemicals based on the ability of carbon to form long chains. Crude oil is mostly a mixture of alkanes, which we will learn more about in this title. These are all hydrocarbons, which only have single bonds. Hydrocarbon molecules have only carbon and hydrogen atoms in them. Chapter two will outline how crude oil is sorted out by fractional distillation into components, according to their boiling point range. A process called 'Cracking' converts alkane hydrocarbons into smaller alkanes and alkenes. Alkenes are also hydrocarbons, but they have a carbon-to-carbon double bond. Alkenes can undergo polymerisation to form polymers. We will consider that combustion of fossil fuels can cause pollution problems, but that we can try to minimise the damage it causes.

Rocks and Building Materials

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Limestone is a raw material used for many chemical processes in industry, and it turns up in some surprising places. Limestone formed from the build up of sediment from the remains of sea creatures, which became stuck together to form this sedimentary rock. Chemically, limestone is almost entirely calcium carbonate. Knowing the chemical nature of limestone can help us to understand some of its reactions, especially the lime cycle. Limestone is widely used in the building trade, not just as the raw stone but also to make cement and concrete. Although limestone is very useful as a raw material, it must be noted that limestone quarries cause environmental problems. A balance is needed between exploiting this valuable resource and damage to the countryside and people's lives. As we will consider, it is sometimes difficult to achieve this.

Atomic Structure

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

This title will start by considering the small pieces which all matter is made from. These are called 'particles'. We will identify everyday events that can only be explained by matter being made up of particles. Secondly, the title will move on to look at atoms and what they are made of. It considers protons, neutrons and electrons as the building blocks of atoms. The terms 'atomic number' and 'mass number' are then explained. We will use these concepts to understand what isotopes are. After this, we will introduce the term 'relative atomic mass', before going on to consider the arrangement of the electrons in shells around the nucleus and how this can affect the chemical properties of the elements. Finally, the title looks at the terms 'element', 'mixture' and 'compound' and what they mean to scientists.

Bonding

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

The electrons in the outside shells of atoms are responsible for bonding. Therefore, it is important to know how many electrons there are in the outside shell of each atom. There are three types of chemical bond: metal atoms join to non-metal atoms by ionic bonding, non-metal atoms join to other non-metal atoms by covalent bonding, and metal atoms join by metallic bonding. By understanding how atoms join together on an individual basis, we can build up a picture of how millions of atoms join together, and relate this to the physical properties of the material.

Mixtures

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Solid, liquid and gas are the three states of matter, and mixtures of them can be formed in a variety of ways. The simplest kind of mixture is a solution. The solid disappears because it is broken up into particles that are too small to be seen. We can measure how much solid dissolves in a certain mass of liquid. This is called the solubility. In a suspension, the particles are small enough so that they don't settle out as sediment but are just large enough to be seen. A suspension is one kind of colloid. Colloids are substances that have mixtures of states. A jelly has some properties like a solid and some like a liquid. Some very useful materials are mixtures. These include emulsions, solutions and alloys. We will consider the various types of mixtures in this title.

Representing Reactions

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

We start this title by looking at how we can make a word equation describe a chemical change. Next we'll look at how to get the chemical formula correct for the substances in the word equation, as we make it into a balanced chemical equation. We will consider the mystery of large numbers and subscripts. Another problem to learn about is 'diatomic gases', and why sometimes an element needs a small two in the equation. Once we can write chemical equations, we can start to use them. We can predict how much material is made by a reaction using the concept of the mole' and relative formula masses. Then we will look at two more complicated ideas - percentage yield and percentage atom economy. Finally, we will look at the periodic table and the patterns within its groups and periods.

Alkali Metals and Transition Metals

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

This title covers the two groups of metals you need to know about in detail for your GCSEs. These are the alkali metals and the transition metals. We will first describe the general properties of the alkali metals, then discuss in more detail how these metals react with water, before moving on to discuss the properties of the transition metals. This leads on to looking at the wide-ranging uses of these metals. To finish, we will compare the two groups to highlight the similarities and differences between them.

Chemicals from Calcium Carbonate

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

This title is all about the chemistry of calcium carbonate. This is a naturally occurring mineral that can take many different forms. Most often, it is quarried as the sedimentary rock limestone. Calcium carbonate is a very versatile compound that can be used for many different things, as we will learn. We will also examine in detail some of the chemical reactions that calcium carbonate is involved in.

Chemicals From Salt

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Sodium chloride, the chemical name for salt, is a highly valuable compound. In fact, it has been such a valuable product throughout history that it has been used in place of money! In this title, we will look at the different chemicals produced from the electrolysis of sodium chloride in different forms, the processes of electron transfer involved in electrolysis and the uses of the products that are formed.

Non-Metals, Noble Gases and Halogens

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

This title is concerned with the non-metallic elements, found on the right-hand side of the periodic table. Throughout this title, we will explore the diverse range of properties of these elements and describe some of the variety of applications they can be used for. In the later chapters, we will focus on two specific groups of non-metals, the halogens and the noble gases. For each group, we will consider the properties that the elements within the group share, and describe any changes in properties you may see between the elements of the group.

The Periodic Table, Elements and Compounds

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

The world of chemistry can seem very confusing, with so many different types of substance, all reacting in so many different ways. A few rules can help remove this confusion, and the periodic table is a very useful resource to help us do this. In this title, we will explore the nature of different elements and explain why there is so much variety in the compounds that can be made. We will also discuss the history and organisation of the periodic table, as well as exploring the trends and patterns that can be found within it.

Energy Transfer with Reactions

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Everyone knows that a ball runs downhill until it reaches a big enough obstacle to stop it, or a pencil can rest on a tabletop but could lose energy by falling to the floor. These observations are obvious in everyday life, but harder to explain in terms of chemistry. First, we need to understand about endothermic and exothermic changes. Endothermic changes have heat supplied to the chemicals in a reaction, whereas exothermic ones have heat released from the chemicals. Calorimetry is the science of measuring the heat transfer in a chemical reaction. We will look at combustion as a source of heat energy, and find out why some burning reactions cause explosions and why some just glow gently. Flammability can be useful but also dangerous, so we will conclude this title with a consideration of hazard symbols.

Rates of Reaction

feeds@gcsepod.co.uk (GCSEPod Feeds) — Thu, 01 Jan 1970 01:00:00 +0100

Chemical reactions are occurring inside us and around us all the time, but the rate or speed at which they occur varies massively. It can take a tenth of a second for a firework to explode in the sky, take hours for an apple to turn brown or for your body to digest a piece of meat, but take years for a piece of iron to rust completely. In the chemical industry it is crucial for scientists to understand reaction rates when useful chemicals are being produced on a large scale. The company needs reactions to happen quickly to make the process economical, but also at a rate that is safe: explosions are exceptionally fast chemical reactions! This title looks at why reaction rates vary so much and the conditions needed to control reaction rates.