|
Erstellt von emilydee43
vor mehr als 11 Jahre
|
|
Some materials gain an electrostatic charge when rubbed together. opposite charges attract, like repel
Electric current is the flow of charge arouond the circuit
The potential difference between 2 points in an electronic circuit is the work done (energy transferred) per coulomb of charge that passes through the points
Circuit symbols represent electrical components
Resistance is a measure of how difficult it is for electrons to pass through a component
Current must pass through all components in a series circuit one after the other. Current in parallel can take more than one route
the resistance of a filament lamp increases as its temperature increases
An LED (light emitting diode) produces light when a current flows through it, and is efficient and long-lasting.
The resistance of an LDR (light-dependant resistor) varies with intensity of light. LDR's are used in switches
The resistance of a thermistor varies as its temperature changes. thermistors are often used in temperature sensors
Electric current has two forms; direct current (d.c) usually produced by batteries or cells alternating current (a.c) such as UK mains electricity (230 V a.c with frequency 50 Hz)
UK three-pin plugs contain a live wire (brown), a neutral wire (blue), an earth wire (green and yellow), and a fuse. Fuses, earth wires, and circuit breakers are safety devices
When an electric charge flows through a resistor, energy is transferre. Larger appliences need larger power cables. the power of an appliance is its rate of energy transfer.
Atoms have small central nucleus of protons (positively charged) and neutrons (no charge) surrounded by negatively charged elesctrons in orbit. Positively or negatively charged ions are created when atoms gain or lose electrons
Isotopes are atoms with the same number of protons/atomic number but a different number of neutrons
Radioactive decay is the breakdown of the nucleus of an atom to formionising radiation. Half-life is the average time taken for activity (decays per second) to halve
Nucleur fission is used in nuclear reactors to produce electricity
Nucleur fusion produces energy in stars
Rate of reaction is the change in amount of product (or reactant) per second
Reactions are faster at higher temperatures, at high concentration and high pressure, and with powdered solids.
Activation energy is the minimum amount of energy particles need to react
Catalyst increase the rate of a reaction but are unchanged at the end. they reduce the cost of industrial reaction
some reactions (e.g. combustion) are exothermic (transfer energy to the surroundings)
Some reactions (e.g. thermal decomposition) are endothermic (takes in energy from surroundings)
Reversable reactions are endothermic in one direction and exothermic in the other
Acids have a pH of less than 7 and are neutralised by bases
Metal oxides or hydroxides are bases, ammonia is also a base
Alkalis are bases dissolved in water. they have a pH of greater than 7
Acids contain H+ ions, alkalis contain OH- ions. these react to form water
Salt form when acids react with bases, alkalis or reactive metals
Soluble salts are prepared by neutralisation followed by crystallisation
Insoluble salts are made by precipitation reactions
Precipitation is used in water treatment
in electrolysis an electric current is passed through an ionic compound (molten or in soluation) . the compound breaks down into elements
Reduction happens at the negative electrode. Positive ions gain electrons. (RED CAT)
Oxidation happens at the positive electrode. Negative ions lose electrons
Metal objects are electroplated by making them a negative electrode and placing them in a solution of suitable ions
Aluminium is extracted by electrolysis of molten bauxite dissolved in cryolite
Electrolysis of brine produces chlorine, sodium hydroxide, and hydrogen
New Page
Chemisrty
Möchten Sie kostenlos Ihre eigenen Notizen mit GoConqr erstellen? Mehr erfahren.