Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chemistry Revision (Acids and Alkalis (Keywords (pH: Scale of acidity and…
Chemistry Revision
Acids and Alkalis
The pH of a solution depends on the strength of the acid: strong
acids have lower pH values than weak acids.
Mixing an acid and alkali produces a chemical reaction,
neutralisation, forming a chemical called a salt and water.
Fact: Acids have a pH below 7, neutral solutions have a pH of 7,
alkalis have a pH above 7.
Fact: Acids and alkalis can be corrosive or irritant and require
safe handling.
Fact: Hydrochloric, sulfuric and nitric acid are strong acids.
Fact: Acetic and citric acid are weak acids.
Keywords
pH: Scale of acidity and alkalinity from 0 to 14.
Indicators: Substances used to identify whether unknown solutions are acidic or alkaline.
Base: A substance that neutralises an acid �those that dissolve in water are called alkalis.
Concentration: A measure of the number of particles in a given volume.
Periodic Table + Elements
The elements in a group all react in a similar way and sometimes show a pattern in reactivity.
As you go down a group and across a period the elements show patterns in physical properties.
Fact:
Metals are generally found on the left side of the table, non-metals on the right.
Group 1 contains reactive metals called alkali metals.
Group 7 contains non-metals called halogens.
Group 0 contains unreactive gases called noble gases.
Keywords
Periodic table: Shows all the elements arranged in rows and columns.
Physical properties: Features of a substance that can be observed without changing the substance itself.
Chemical properties: Features of the way a substance reacts with other substances.
Groups: Columns of the periodic table.
Periods: Rows of the periodic table.
Most substances are not pure elements, but compounds or mixtures containing atoms of different elements. They have different properties to the elements they contain.
Skill: Use particle diagrams to classify a substance as an element, mixture or compound and as molecules or atoms.
Skill: Name simple compounds using rules: change non-metal to �ide; mono, di, tri prefixes; and symbols of hydroxide, nitrate, sulfate and carbonate.
Fact: The symbols of hydrogen, oxygen, nitrogen, carbon, hydrogen, iron, zinc, copper, sulfur, aluminium, iodine, bromine, chlorine, sodium, potassium and magnesium.
Keywords
Elements: What all substances are made up of, and which contain only one type of atom.
Atom: The smallest particle of an element that can exist.
Molecules: Two to thousands of atoms joined together. Most non-metals exist either as small or giant molecules.
Compound: Pure substances made up of two or more elements strongly joined together.
Chemical formula: Shows the elements present in a compound and their relative proportions.
Polymer: A molecule made of thousands of smaller molecules in a repeating pattern. Plastics are man-made polymers, starch is a natural polymer.
Separating Mixtures
A pure substance consists of only one type of element or compound and has a
fixed melting and boiling point. Mixtures may be separated due to differences in
their physical properties.
The method chosen to separate a mixture depends on which physical
properties of the individual substances are different.
Skill: Use techniques to separate mixtures.
Fact: Air, fruit juice, sea water and milk are mixtures.
Fact: Liquids have different boiling points.
Keywords
Solvent: A substance, normally a liquid, that dissolves another substance.
Solute: A substance that can dissolve in a liquid.
Dissolve: When a solute mixes completely with a solvent.
Solution: Mixture formed when a solvent dissolves a solute.
Soluble (insoluble): Property of a substance that will (will not) dissolve in a liquid.
Solubility: Maximum mass of solute that dissolves in a certain volume of solvent.
Pure substance: Single type of material with nothing mixed in.
Mixture: Two or more pure substances mixed together, whose properties are different to the individual substances.
Filtration: Separating substances using a filter to produce a filtrate (solution) and residue.
Distillation: Separating substances by boiling and condensing liquids.
Evaporation: A way to separate a solid dissolved in a liquid by the liquid turning into a gas.
Chromatography: Used to separate different coloured substances.
Metals and non Metals
Metals and non-metals react with oxygen to form oxides which
are either bases or acids.
Metals can be arranged as a reactivity series in order of how
readily they react with other substances.
Some metals react with acids to produce salts and hydrogen.
Fact: Iron, nickel and cobalt are magnetic elements.
Fact: Mercury is a metal that is liquid at room temperature.
Fact: Bromine is a non-metal that is liquid at room temperature.
Keywords
Metals: Shiny, good conductors of electricity and heat, malleable and ductile, and usually solid at room temperature.
Non-metals: Dull, poor conductors of electricity and heat, brittle and usually solid or gaseous at room temperature.
Displacement: Reaction where a more reactive metal takes the place of a less reactive metal in a compound.
Oxidation: Reaction in which a substance combines with oxygen.
Reactivity: The tendency of a substance to undergo a chemical reaction.
Reactions
During a chemical reaction bonds are broken (requiring energy) and new bonds formed (releasing energy). If the energy released is greater than the energy required, the reaction is exothermic. If the reverse, it is endothermic.
Keywords
Catalysts: Substances that speed up chemical reactions but are unchanged at the end.
Exothermic reaction: One in which energy is given out, usually as heat or light.
Endothermic reaction: One in which energy is taken in, usually as heat.
Chemical bond: Force that holds atoms together in molecules.
Combustion is a reaction with oxygen in which energy is transferred to the surroundings as heat and light.
Thermal decomposition is a reaction where a single reactant is broken down into simpler products by heating.
Chemical changes can be described by a model where atoms and molecules in reactants rearrange to make the products and the total number of atoms is conserved.
Skill: Write word equations from information about chemical reactions.
Keywords
Fuel: Stores energy in a chemical store which it can release as heat.
Chemical reaction: A change in which a new substance is formed.
Physical change: One that changes the physical properties of a substance, but no new substance is formed.
Reactants: Substances that react together, shown before the arrow in an equation.
Products: Substances formed in a chemical reaction, shown after the reaction arrow in an equation.
Conserved: When the quantity of something does not change after a process takes place.
Particle Models
Properties of solids, liquids and gases can be described in terms of particles in motion but with differences in the arrangement and movement of these same particles: closely spaced and vibrating (solid), in random motion but in contact (liquid), or in random motion and widely spaced (gas).
Observations where substances change temperature or state can be described in terms of particles gaining or losing energy.
Fact
A substance is a solid below its melting point, a liquid above it, and a gas above its boiling point.
Keywords
Particle: A very tiny object such as an atom or molecule, too small to be seen with a microscope.
Particle model: A way to think about how substances behave in terms of small, moving particles.
Diffusion: The process by which particles in liquids or gases spread out through random movement from a region where there are many particles to one where there are fewer.
Gas pressure: Caused by collisions of particles with the walls of a container.
Density: How much matter there is in a particular volume, or how close the particles are.
Evaporate: Change from liquid to gas at the surface of a liquid, at any temperature.
Boil: Change from liquid to a gas of all the liquid when the temperature reaches boiling point.
Condense: Change of state from gas to liquid when the temperature drops to the boiling point.
Melt: Change from solid to liquid when the temperature rises to the melting point.
Freeze: Change from liquid to a solid when the temperature drops to the melting point.
Sublime: Change from a solid directly into a gas.