Take This Ultimate Year 8 Chemistry Test

Silicon and Carbon are non-metallic solids, and Neon is a non-metallic gas.

It is a chemical formula that represents a molecule of water, which is a fundamental and essential substance for life. Water contains 2 hydrogen atoms and one oxygen atom.

Magnesium ---- Mg
Potassium --- K (Kalium)
Sodium --- Na (Natrium)
Silicon ---- Si

 An atom has 3 different subatomic particles known as protons, neutrons, and electrons. The protons and neutrons are found in the middle of the atom in the nucleus, and the nucleus is surrounded by electrons orbiting the nucleus.

The reactants (starting or raw materials) are Magnesium and Oxygen in the air.
The products are Magnesium oxide - white ash, and the bright white light and heat energy.

Non-metals have properties very different from Metals - many are the opposite.
They are brittle, not shiny, and poor conductors of heat and electricity.

The element exhibits metallic properties as it is shiny, indicating a reflective surface, bendable, signifying malleability, and functions as a good conductor of electricity, showcasing typical traits of metals. These characteristics align with the general properties observed in metallic elements within the periodic table.

Sodium is a very reactive metal that is normally combined with other elements to form compounds in nature - e.g., NaCl (salt). Copper, gold, and silver are less reactive than sodium and are typically found in nature as pure substances embedded into rocks.

An element is a pure substance that consists of only one kind of atom. An atom can't be broken down into smaller particles (substances). There are 118 elements found in the periodic table.

An atom is the smallest particle of a substance.
An element consists of only one kind of atom that can't be broken into other substances.
A compound is a substance made of two or more elements chemically combined.
A mixture is a substance made of two or more elements and/or compounds that can be separated by physical means.

Most atoms are made up of three fundamental subatomic particles Electrons, protons and neutrons.

A molecule is the smallest existing form of a chemical - it consists of 2 or more atoms of the same or different atoms bonded together. Oxygen exists as O2, nitrogen as N2, and carbon dioxide as CO2. Neon belongs to the last group of elements in the periodic table. It exists as a single atom instead of a molecule, and so do helium and argon.

 Sublimation is a process of changing the state in which a solid changes directly into gas on heating. Element iodine is a black crystal (but non-metal) that changes to a purple vapor on heating; there is no liquid iodine as such. Carbon dioxide (in the form of Dry Ice) also changes (sublimes) to a gas (carbon dioxide) directly at room temperature and pressure.

A physical change normally involves a change in state and shape. It is usually reversible, and no new substances are formed. A chemical change (reaction) produces new substances and is normally irreversible.

 A precipitate is a solid that may be formed from mixing 2 solutions. A precipitate will often settle to the bottom of a reaction vessel after some time.

The larger number is the mass number = protons + neutrons. The smaller number is the atomic number of an element = protons = electrons. So, the neutron number can be found by subtracting the protons from the mass number 27-23 = 14 neutrons