The magnetic quality of ancient rocks is called paleomagnetism. It <span>is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form.</span>
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A catalytic converter changes nitrogen dioxide to nitrogen gas and oxygen gas is a chemical change.
Explanation:
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In this case, since physical changes do not modify the molecular composition and structure of the material undergoing it whereas the chemical change does, for catalytic converters we should know they promote chemical reaction in which the composition is changed; for instance, for the given example, the following chemical reaction is the evidence:

As you can see, nitrogen and oxygen are no longer bonded but separated by themselves, therefore, this is a chemical change.
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In an atom, the number of neutrons determines most specifically the isotopes of an element.
<h2>Further Explanation</h2><h3>An atom </h3>
- An atom is defined as the smallest particle of an element that can take part in a chemical reaction.
- Atoms are made of energy shells and the inner nucleus.
- It is also made up of subatomic particles, protons and neutrons.
<h3>Neutrons </h3>
- They are sub-atomic particles in an atom that are found in the nucleus of an atom. They have a zero charge or no charge.
- Neutrons are slightly heavier than protons.
- The number of protons and neutrons in a nucleus of an atom results to the atomic mass number of an atom. Like protons they only take part in nuclear reactions.
<h3>Protons</h3>
- Protons are subatomic particles that are found in the nucleus of an atom. They are positively charged. with a charge of +1.
- The number of protons differ from one element to another and thus used as the atomic number of an individual element.
- The nucleus of an atom is positively charged due to the positive charge of the protons.
- Additionally, protons do not take part in chemical reactions but in nuclear reactions.
<h3>Electrons </h3>
- They are found orbiting the nucleus on energy shells based on Clouds’ theory. Electrons are negatively charged each with a charge of -1.
- The number of electrons and protons in a neutral atom are equal. Additionally they have the least mass of the three sub-atomic particles.
- Electrons are the only sub-atomic particles that take part in chemical reactions.
<h3>Isotopes </h3>
- Isotopes are atoms of the same element that have the same mass number but different atomic number.
<h3>Mass number;</h3>
- Mass number is the sum of the number of protons and neutrons in the nucleus of an atom of an element.
Keywords: Atom, sub-atomic particles, electrons, protons, neutrons, isotopes
<h3>Learn more about:</h3>
Level: High school
Subject: Chemistry
Topic: Atomic structure