GCSE Combined Science (AQA)
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Atomic structure and the periodic table
A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes
Chemical Reactions
1:48
Chemical Reactions and Equations
Spec
4.1.1.1
4.3.1.1
- In chemical reactions, atoms and molecules react to form new substances.
- Example: Hydrogen (H2) and oxygen (O2) react to form water (H2O).
- Chemical reactions often involve a detectable energy change.
- Energy change can be measured with a thermometer, showing a change in temperature.
- Large temperature changes can be felt as warm or cool.
- Compounds are formed from elements through chemical reactions.
- Example: Magnesium (Mg) and sulfur (S) react to form magnesium sulfide (MgS).
- Compounds are different from the original elements.
- Compounds can only be separated back into elements by chemical reactions.
- Magnesium and sulfur in magnesium sulfide cannot be separated without a reaction.
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