Topic Test Flashcards
J.J. Thompson
Devised the plum pudding model. Shows negatively charged electrons embedded in a positively charged sphere.
Democritus
First suggested matter was made up of atoms, 2500 years ago
Current atom model
Nucleus is tiny and is made up of protons and neutrons, surrounded by electrons.
John Dalton
His theory proposed that all matter consisted of tiny particles called atoms. Atoms cant be divided into smaller particles, atoms of the same element are alike, atoms combined in one are called compounds
Lord Rutherford
His model was same as today except it proposed orbiting electrons would lose energy and would collide back into the nucleus.
Niels Bohr
Studied with Rutherford. Proposed different energy levels in electrons around nucleus. To go to different levels electron energy is gained or lost.
Sir James Chadwick
Discovered nucleus contained neutrons and proton. Neutrons have no charge.
Nucleus
Small, very dense. Contains neutrons and protons. Nucleus makes up almost all atom’s mass. Neutrons and protons held together by very strong nuclear force.
Protons
Found in nucleus. Has positive charge
Neutrons
Found in nucleus. Has no charge
Electrons
Orbit around nucleus. Path followed referred to as electron cloud. Have negative charge, number of electrons in atom is equal to number of protons in nucleus.
Atom
Makes up matter. Electrically neutral. Consists of protons, neutrons and electrons
Chemical reaction
Chemical reactions take place when bonds between atoms break down and new bonds are formed. Changes that can take place; temperature, colour, formation of gas or solid, odour.
Sometimes energy is required to start reaction (eg. Light, heat, electric current).
Product
New substance produced due to chemical reaction
Reactant
Original substance that makes a chemical reaction
Antoine-Laurent Lavoisier
His ideas led to the law of conservation of mass and law of constant proportions
Law of conservation of mass
States that matter can neither be created nor destroyed during a chemical reaction.
Law of constant proportions
States a compound always contains the same relative amounts of each elements
Isotopes
Atoms of the same element but that have a different mass.
See notes for isotope representation
stable atom
Proton and neutron in nucleus held together very strongly
Unstable atom
Neutrons and protons in nucleus aren’t held together strongly
Radiosotope
Isotope that is unstable
Natural radioactivity
Emitted from matter without energy being supplied to atom
Artificial radioactivity
Made by bombarding the atoms with sub-atomic particles like protons and neutrons
Nuclear radiation
Energy emitted by radioactive substance
3 types of nuclear radiation
Alpha particles
Beta particles
Gamma rays
Alpha particles
Most charged
Heaviest
Bends in magnetic field
Stopped by paper
Beta particles
More penetrating Stopped by aluminium Bend to left in magnetic field Lighter Negative charge
Gamma radiation
Stopped by lead Goes furthest Most penetrating Not particle Pure energy No charge
Half life
Time taken for half of radioactivity to decay
Nuclear reactor
Creates electricity by using radioactivity
Exothermic reaction
Reaction which gives out energy
Endothermic reaction
Reaction which absorbs energy
Acid
Anything with a pH level under 7
Corrosive
Has sour taste
Prevents growth of microorganisms
Corrosive
Eats away at solid substances
Bases
Have a bitter taste
Slippery or soapy to touch
Some a very corrosive
Bases that can be dissolved are called alkalis
Acid-base indicator
Substance used to tell wether a substance is an acid or base
Litmus
Is an acid-base indicator
Turns red in acid
Turns blue in base
Bromothymol
Is an acid-base indicator
Turns yellow in acid
Turns bluish-purple in a base.
pH scale
Used to describe how acidic or basic a substance is. Numbers range from 0-14 0 is most acidic 14 is most basic 7 is neutral
Universal indicator
Mixture of indicators
Colours change as strength of acid and bases change.
Used to measure the pH
Neutralisation
When acid and base mix it creates salt and water
Acid rain
Rain that has a pH of 4.2-4.4
Consists of:
NO -> nitric acid
SO2 -> Sulfur is acid
Artificial source of SO2 and NO
Fossil fuels
Electric power generation
Oil refineries
Natural source of SO2 and NO
Volcano
Negative acid rain effects on Marine life
Acid goes in soil then into lakes, rivers and oceans. At pH 5 eggs cant hatch. At pH 4 kills off adult fish and plants.
Negative acid rain effects on land
Removes nutrients in soils affecting trees. Damages cells on leaves and affects the flow of water.
Neutralise
To stop something from having an effect
Indigestion
Caused when you eat too quickly or too much of the wrong food and contents of stomach increase in acidity.
Hydrochloric acid in stomach is under 1.5
Result of mixing an acid and metal
Creates a salt and hydrogen
Combustion reaction
Reaction which a substance reacts with oxygen to produce heat.
Fuel
Substance reacting with oxygen in a combustion reaction
Fossil fuels
Fuel made of remains of living things.
Are compounds of hydrogen and carbon called hydrocarbon
Uses for combustion reactions
Cooking (methane) Powering car (octane) Planes (kerosene) Oxidation Making electricity (coal) Respiration (glucose) Powering a rocket (hydrogen)
Respiration
Takes place in every cell of your body
Slow combustion reaction
Happens when glucose from digested food reacts with oxygen that you breathe in. Produces carbon dioxide.
Radiometric dating
Can be used to determine age of rocks and fossils.
Usually uses Isotope carbon-14 as it has a half-life of 5700 years. Radiometric dating using carbon called radiocarbon dating.
All living things contain radiocarbon. When living things die the decaying radiocarbon is being replaced isn’t being replaced therefore age of fossil or rock can be measured.
Radiocarbon
A small amount of carbon
How nuclear reactors work
Uranium is converted into uranium dioxide and sealed into rods called fuel rods.
Fuel rods undergo fission reaction when neutrons are fired at radioactive uranium.
Causes uranium nuclei to split and form two new elements, releasing neutrons, radiation and heat.
Heat is used to heat water producing steam which spins turbines.
Radiotherapy
Use of radioisotopes to kill cancer cells or prevent them from multiplying. Can be targeted to small area so surrounding tissue not damaged.
Negative uses for radioactivity
Nuclear weapons
Malfunctioning nuclear reactors
Causes cancers
Damaging cells in living things.
