Chemistry Basics for Grade 8

What is a chemical reaction?

• A chemical reaction is a physical change in matter.

• A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.

• A chemical reaction is a mathematical equation.

• A chemical reaction is a biological process.

What are atoms made of?

• Quarks, leptons, and bosons

• Molecules, compounds, and mixtures

• Photons, gravitons, and gluons

• Protons, neutrons, and electrons

What are the three subatomic particles and their charges?

• Protons have a positive charge, neutrons have a positive charge, and electrons have a negative charge.

• Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.

• Protons have a negative charge, neutrons have no charge, and electrons have a positive charge.

• Protons have a negative charge, neutrons have a positive charge, and electrons have no charge.

Explain electron configuration in an atom.

• Electron configuration is determined by the number of neutrons in an atom

• Electron configuration is represented by a single letter in the periodic table

• Electron configuration refers to the arrangement of protons in an atom

• Electron configuration is the arrangement of electrons in an atom, typically represented by a series of numbers and letters that denote the energy levels and sublevels occupied by electrons.

What is the basic unit of life that involves chemistry?

• molecule

• cell

• atom

• organism

How is the periodic table organized?

• By grouping elements randomly

• By organizing elements alphabetically

• By increasing atomic number and grouping elements with similar properties together.

• By arranging elements based on their melting points

What do periods and groups represent in the periodic table?

• Periods represent the number of valence electrons, and groups represent the number of electron shells.

• Periods represent the number of electron shells, and groups represent the number of valence electrons.

• Periods represent the number of electrons in the nucleus, and groups represent the number of electrons in the outermost shell.

• Periods represent the number of protons, and groups represent the number of neutrons.

Define relative atomic mass.

• The total mass of an element's atoms

• The average mass of an element's atoms compared to the mass of a carbon-12 atom.

• The mass of an element's most common isotope

• The mass of an element's electrons

What are isotopes?

• Different elements with the same number of neutrons.

• Molecules with the same atomic number.

• Atoms of different elements with different numbers of protons.

• Atoms of the same element with different numbers of neutrons.

Explain the concept of ions.

• Ions are always positively charged.

• Ions are charged particles formed by gaining or losing electrons.

• Ions are neutral particles formed by gaining or losing electrons.

• Ions are only formed by gaining electrons.