AQA GCSE Chemistry Unit 1 Higher Verified Guide

AQA GCSE Chemistry Unit 1 Higher Verified Guide 1. What is the smallest unit of an element that can exist, composed of protons, neutrons, and electrons? Answer: The atom is the smallest unit of an element that can exist. 2. How do elements differ from compounds and mixtures? Answer: Elements are made up of one kind of atom, whereas compounds are formed by combining two or more elements chemically, and mixtures are a combination of two or more substances that are not chemically combined. 3. What is the process of separating a solid from a liquid? Answer: Filtration is the process of separating a solid from a liquid. 4. What is the reaction between Group 1 metals and water? Answer: Group 1 metals react with water to form metal hydroxides and hydrogen gas. 5. What is the process of forming crystals as a solvent evaporates from a solution? Answer: Crystallization is the process of forming crystals as a solvent evaporates from a solution. 6. What is the process of separating substances in a solution based on their boiling points? Answer: Distillation is a process that separates substances in a solution based on their boiling points. 7. What is the technique used to separate substances using solvent and chromatography paper? Answer: Chromatography is a technique used to separate substances using solvent and chromatography paper. 8. Who proposed the Plum Pudding Model of an atom? Answer: J.J. Thomson proposed the Plum Pudding Model of an atom, which suggested that electrons were randomly distributed within a positively charged cloud. 9. What was Rutherford's Gold Foil Experiment? Answer: Rutherford's Gold Foil Experiment involved directing alpha-particles at a thin sheet of gold foil and observing how they interacted with it, leading to the discovery of the atomic nucleus. 10. What are the charges and masses of protons, neutrons, and electrons? Answer: Protons have a charge of +1 and a mass of 1, neutrons have no charge and a mass of 1, and electrons have a charge of -1 and almost zero mass. Size of an atom ️1 x 10^-10 m Size of nucleus ️1 x 10^-14 m Mass number ️Sum of protons and neutrons in an atom (top number in the periodic table) Atomic number ️Number of protons in an element (bottom number in the periodic table) Relative atomic mass ️Average mass of an element given the percentage abundance of its isotopes Isotopes ️Atoms of the same element that have different numbers of neutrons Electronic Structure ️Electrons in an atom occupying the lowest energy shells e.g. 2,8,8,2 Periodic Table ️A table that shows the elements, their atomic number, symbol, and average atomic mass; elements with similar chemical properties are grouped together. Groups of the periodic table ️vertical columns Mendeleev ️Russian chemist who developed a periodic table placing elements in order of atomic weight and based on their properties, leaving gaps when necessary Metals ️Elements that react to form positive ions (found to the left of the periodic table) Non-metals ️Elements that do not form positive ions (found to the right of the periodic table) Group 0 ️Noble Gases, Unreactive as their atoms have stable arrangements of electrons. Boiling points decrease down the group. Group 1 ️Alkali metals, Contain 1 electron in their outer shell Reactivity of group 1 ️Increases down the group as their are more electron shells so the electron that is removed is further from the positive nucleus, so the attraction between the nucleus and electron is weaker, so easier to lose. Group 1 + Oxygen ️Group 1 metals react with the air to form metal oxides. E.g. Li2O Group 1 + Chlorine ️Reaction forms metal chloride e.g. LiCl Group 7 ️Halogens, All have 7 electrons in their outside shell, Halogens exist by themselves as a pair of atoms bonded Reactivity of group 7 ️Decreases down the group as their are more electron shells so the electron that is added is further from the positive nucleus, so the attraction between the nucleus and electron is weaker, so harder for the electron to be added Fluorine ️Pale yellow gas Chlorine ️Pale green gas Bromine ️Brown liquid Iodine ️Grey solid Proton ️Mass of 1 Charge of +1, found in the nucleus of an atom Neutron ️Mass of 1 Charge of 0, found in the nucleus of an atom Electron ️Mass is very small Charge of -1, found in shells of an atom Nucleus ️Centre of an atom, contains protons and neutrons