Year 11 Chem - Module 1 questions and answers latest update

Year 11 Chem - Module 1 questions and answers latest updateMixture A combination of two or more pure substances in which each pure substance retains its individual chemical properties. Heterogeneous Mixtures Two or more substances intermingle but remain physically separate. Possible to separate the original ingredients by simple physical means, such as filtering, centrifuge, decanting or sedimentation. Examples: dirt + sand, oil + water, salt + baking soda 01:10 01:33 Homogeneous Mixtures Two or more substances have merged into a uniform phase. No borders between the substances, not chemically bonded, physical properties of each ingredient can be exploited to separate them. Examples: saltwater, copper sulfate solution Examples of Physical Properties Magnetism, solubility, density, boiling point, melting point, particle size. Filtration A process that separates materials based on the size of their particles. Example: Solid Impurities in a solution separated and left as residue. Liquid collected called filtrate. Decantation Separates liquid from solid precipitate by pouring off liquid without disturbing solid. Example: Grains of sand in water can be separated using this method. Distillation A process that separates the substances in a solution based on their boiling points. Gas is cooled and turned back into liquid. Example: Boiling saltwater to get salt and water. Fractional Distillation Separation of a liquid mixture into fractions differing in boiling point, typically using a fractionating column. Example: Crude oil. Evaporation Changing the state of a liquid to a gas while leaving a solid. Example: Boiling saltwater without keeping the water. Centrifuging Technique used to separate light from heavy particles by rapidly spinning the mixture. Example: Separating the red blood cells in blood. Sieving Separating particles of different sizes by allowing the smaller particles to fall through holes in a container. Example: Pebbles and sand. Magnetic Separation A method of separating magnetic materials from nonmagnetic ones. Example: Separating iron filings out of dirt. 00:02 01:33 Chromatography A technique that is used to separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material. Example: Separating colours in ink with paper. Separating Funnel A pear-shaped glass container, with a tap at its base, used to separate two liquids that do not mix. Opening the tap removes the bottom liquid and the liquid floating on top is left in the funnel. Example: Separating water and oil. Percentage Composition Equation % composition = (grams of element / grams of compound) x 100 Elements are... Pure substances that cannot be chemically or physically decomposed. Compounds are... Pure substances that are chemical combinations of two or more different elements and can be decomposed. Periods are... Horizontal rows on the periodic table. Each corresponds to the number of electron shells the element has. Groups are... Vertical columns on the periodic table. Elements share similar chemical properties, same number of valence electrons. Metals are... Good conductors of heat and electricity, malleable and ductile, usually have a silvery shine, solid at room temperature (except mercury). Non-metals are... Usually good insulators of heat and electricity, brittle, usually dull, many are gases at room temperature, some liquids, some solids. Metalloids are... Combinations (have properties) of both metals and non-metals, can be made to conduct electricity in some circumstances. Alkali Metals Group 1, all elements have one valence electron. Alkali Metals Physical properties: soft, lustrous metallic solids, low densities, high thermal and electrical conductivity, relatively low melting point Alkali Metals Chemical properties: highly reactive, vigorous exothermic reaction with water and oxygen, present naturally as salts Alkaline Earth Metals Group 2, all elements have two valence electrons. Alkaline Earth Metals Physical properties: lustrous metallic solids, high thermal and electrical conductivity, more dense, higher melting points and harder than alkali metals Alkaline Earth Metals Chemical properties: reactive, oxidise easily, exothermic reaction with water Transition Metals Groups 3-12, elements having varying valencies. Transition Metals Physical properties: white, hard, lustrous, dense metallic solids, high thermal and electrical conductivity, high melting points Transition Metals Chemical properties: less reactive than alkali metals, but chemical properties otherwise vary Halogens Group 17, all elements have 7 valence electrons Halogens Physical properties: non-metals, melting and boiling points increase going down the column, halogens change state going down the column, poor thermal and electrical conductivity, unpleasant odours, very toxic Halogens Chemical properties: highly reactive, form ions with -1 charge, form diatomic molecules Noble Gases Group 18, all elements have full valencies (8 valence electrons) Noble Gases Physical properties: gases, low boiling points, low densities Noble Gases Chemical properties: highly unreactive, mostly present as monatomic gases, very rarely form compounds Atomic Radius Half the distance between the centres of two atoms of an element that are touching. Affects all the other properties, easier for atom with greater atomic radius to lose electron, because valence shell is further away from nucleus. Ionisation Energy The energy required to remove one valence electron from a gaseous atom. Low first ionisation energy - element is metal High first ionisation energy - nonmetal Ionisation Equations 1st ionisation energy: X → X^(+) + e− 2nd ionisation energy: X^(+) → X^(2+) + e− Electronegativity The measure of the ability of an atom to attract electrons for chemical bonding. As atomic radius decreases, it increases. High ___ difference between atoms - more ionic bond Low ___ difference - more covalent bond. Moving Across Periods • Ionisation Energy Increases • Electronegativity Increases • Atomic Radius Decreases Moving Down Groups • Ionisation Energy Decreases • Electronegativity Decreases • Atomic Radius Increases Isotopes Different versions of an element indicated by number of neutrons Example: Hydrogen atom can have 0, 1 or 2 neutrons, but still hydrogen as has 1 proton. Stable Isotopes Sufficient binding energy to keep the nucleus together, do not undergo radioactive decay. Unstable Isotopes Imbalance of neutrons so binding energy can't hold nucleus together properly, undergo radioactive decay to become stable, also known as radioisotopes. Unstable Isotope Atomic Number Atomic number greater than 82. Stable Isotope Atomic Number Less than 20 and a 1:1 proton-neutron ratio are more likely to be stable. All elements with atomic numbers 82 have one or more stable isotopes (except technetium and promethium) Isotope Notation (Name) Name of the element is given, a hyphen and number indicating mass number. Example: helium-3 or carbon-14. Isotope Notation (Symbol) Chemical symbol given, superscript (mass number) on upper left, subscript (atomic number) on bottom left. Example: ^(3);(2)He, or ^(14);(6)C Relative Atomic Mass Relative atomic masses (given in periodic table) are an average of all isotopes of element. Mass Spectrometer Device that uses electromagnetic fields to sort isotopes present in a substance by atomic mass, allows to see how abundant each isotope is. Calculate Relative Atomic Mass In isotopes A-a and A-b: [%A-a (in decimal form)] x (a) + [%A-b (in decimal form)] x (b) = x amu (amu = atomic mass units) Radioactive Decay Atoms decay because forces holding nucleus together aren't strong enough to hold together large nuclei.