IGCSE Chemistry Study Note
1. Define the term "atom" and explain how the idea of the atom has
evolved over time.
🧬 An alom is the smallest particle of an element that con exist and still show the properties
of that element. The idea of the atom has changed over time, os scientific evidence increased.
At first, atoms were though to be tiny, solid, particles that could not be divided. Later
discoveries showed that atoms were more complex than originally believed, which led to the
improved moldels that better explained how aloms behave in chemical reactions. Today's idea
of the atoms is based evidence gathered over on many years, replacing the simple early
models.
2. Describe the structure of an atom according to the modern atomic
model, including the roles of protons, neutrons, and electrons.
🔬 An atom has a tiny, dense nucleus at its centre, which contains protons and neutrons.
Protons have a positive charge, while neutrons have no charge, and together they provide
almost all the mass of the alom. Surrounding the nucleus are electrons, which have a negative
charge and move around the nucleus, in energy level (shell). These electrons occupy most of the
space in the atom, even though they have almost no mass. The arrangement of electrons in
these shells determines how the atom reacts chemically.
3. Differentiate between an element and a compound. Provide
examples of each.
, 🫧 An element is a substance made of only one type of atom and cannot be broken down into
simpler substances. Examples include oxygen (a) and iron (Fe).
🫧 A compound is a substance made of two or more different elements chemically bonded
together. Compounds can be broken down into their elements by chemical reactions. Example
include water (H₂O) and carbon dioxide (co₂).
4. Explain the concept of a mixture. How does it differ from a pure
substance?
🧫 A mixture is made of two or more substances that are not chemicaly joined, and each
substance keeps its own properties, Mixtures can usually be seperated by physical methods,
such as filtration and evaporation. This is different from a pure substance, which contains only
one type of element or compound and has fixed properties throughout. Examples of mixtures,
include air, salt and sand, or sugar in water.
5. Discuss the law of conservation of mass and its relevance to
chemical reactions.
🧪 Understanding atoms, elements, compounds, and mixtures is essential in chemistry because
it explains how substances behave and react with each other. knowing the difference between
elements and compounds helps chemists predict chemical reactions, while underestanding
mixtures allows for seperation, and purification of substances. This knowledge is also
1. Define the term "atom" and explain how the idea of the atom has
evolved over time.
🧬 An alom is the smallest particle of an element that con exist and still show the properties
of that element. The idea of the atom has changed over time, os scientific evidence increased.
At first, atoms were though to be tiny, solid, particles that could not be divided. Later
discoveries showed that atoms were more complex than originally believed, which led to the
improved moldels that better explained how aloms behave in chemical reactions. Today's idea
of the atoms is based evidence gathered over on many years, replacing the simple early
models.
2. Describe the structure of an atom according to the modern atomic
model, including the roles of protons, neutrons, and electrons.
🔬 An atom has a tiny, dense nucleus at its centre, which contains protons and neutrons.
Protons have a positive charge, while neutrons have no charge, and together they provide
almost all the mass of the alom. Surrounding the nucleus are electrons, which have a negative
charge and move around the nucleus, in energy level (shell). These electrons occupy most of the
space in the atom, even though they have almost no mass. The arrangement of electrons in
these shells determines how the atom reacts chemically.
3. Differentiate between an element and a compound. Provide
examples of each.
, 🫧 An element is a substance made of only one type of atom and cannot be broken down into
simpler substances. Examples include oxygen (a) and iron (Fe).
🫧 A compound is a substance made of two or more different elements chemically bonded
together. Compounds can be broken down into their elements by chemical reactions. Example
include water (H₂O) and carbon dioxide (co₂).
4. Explain the concept of a mixture. How does it differ from a pure
substance?
🧫 A mixture is made of two or more substances that are not chemicaly joined, and each
substance keeps its own properties, Mixtures can usually be seperated by physical methods,
such as filtration and evaporation. This is different from a pure substance, which contains only
one type of element or compound and has fixed properties throughout. Examples of mixtures,
include air, salt and sand, or sugar in water.
5. Discuss the law of conservation of mass and its relevance to
chemical reactions.
🧪 Understanding atoms, elements, compounds, and mixtures is essential in chemistry because
it explains how substances behave and react with each other. knowing the difference between
elements and compounds helps chemists predict chemical reactions, while underestanding
mixtures allows for seperation, and purification of substances. This knowledge is also
