Energy Changes Exothermic and endothermic reactions Chemical reactions can take in or give out energy when bonds are broken and formed. Exothermic reactions Energy is released to the surroundings shown by an increase in temperature. e.g. combustion, neutralisation, respiration. Bond making is an exothermic process. The energy change (∆H) in an exothermic reaction is negative […]

Chemical Changes The reactivity series The reactivity series is a list of metals in order of reactivity. Observations of the metals with substances such as oxygen, water have been used to place the metals. The most reactive metals are at the top and the least reactive at the bottom     Hydrogen and carbon are […]

Quantitative Chemistry Relative Atomic Mass (Ar) The relative atomic mass (Ar) of an element is its relative average mass of an atom compared to the mass of an atom of carbon-12. Image: Pixabay   Relative Formula Mass (Mr) The relative formula mass of a compound is the sum of all the relative atomic masses of the […]

The modern periodic table   Image: Pixabay   Elements are arranged in order of atomic number. The columns show the groups. The group number shows the number of electrons in the outer shell. The rows are called periods – the period shows how many shells of electrons there are e.g. Hydrogen and Helium are in […]

Structure, bonding and properties of matter Exam boards: Chemical bonds Atoms need a full outer shell to be stable. They will form chemical bonds in order to become more stable. There are three types of chemical bond:   Ionic   Covalent Metallic Between Metals and non-metals Non-metals and non-metals Metallic elements and alloys Particles Oppositely […]

Elements Elements are made up of only one type of atom. Each atom in an element must have the same atomic number. All the elements on earth can be found in the periodic table. C = Carbon             F= Fluorine               Na = Sodium                K = Potassium   Isotopes An Isotope is an element that has the […]

Using resources   Using the Earth’s resources Humans have always used the earth’s resources to provide themselves with food, water, transport and shelter.  Many of the resources that humans have used in the past are finite and are now running out.   Humans now need to look for sustainable resources that can be used for […]

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Elements Elements are made up of only one type of atom. Each atom in an element must have the same atomic number. All the elements on earth can be found in the periodic table. Each element is given a symbol.   C = Carbon             F= Fluorine               Na = Sodium                K = Potassium   Isotopes An […]

The structure of the atom   Fig 1 – Source: Pixabay What is an atom made up of? An atom is made up of a nucleus containing protons and neutrons. Protons have a positive charge and neutrons have no charge. Electrons are found moving around the nucleus in orbitals or shells. They have a negative […]