Science, Chem - Rate of Reaction, Material Properties, Energy Flashcards
Isotopes
- atoms of the same elements that have the same number of protons, but different numbers of neutron
- most elements exist as a mixture of isotopes
How to calculate (Isotopes)
nucleon no. (top) - proton no. (bottom) = neutrons no.
Meanings
nucleon no. =
proton no. =
________ = ________
- nucleon no. = mass no.
- proton no. = atomic no.
- protons have the same amount as electrons
Atom Orbit
- proton = positive (nucleus)
- neutron = neutral (nucleus)
- electron = negative (shell)
1st shell = 2 electrons
2nd, 3rd, 4th shell = 8 electrons
Group 1 Elements (6)
- alkali metals
=> lithium (Li)
=> sodium (Na)
=> potassium (K)
=> rubidium (Rb)
=> caesium (Cs)
=> francium (Fr)
Group 2 Elements (6)
- beryllium (Be)
- magnesium (Mg)
- calcium (Ca)
- strontium (Sr)
- barium (Ba)
- radium (Ra)
least vigorous ——-> most vigorous
beryllium => magnesium => calcium => strontium => barium => radium
Word equation for group 2
lithium + water –> lithium hydroxide + hydrogen
Group 7 Elements (5)
- fluorine (F)
- chlorine (Cl)
- bromine (Br)
- iodine (I)
- astatine (At)
Group 7 Facts
- also known as halogens
- the bigger the atom the less reactive it is
Rate of Reaction
- how fast the reaction is (time)
- 2 conditions must be met
=> reactant particles must collide
=> reactant particles must have sufficient energy - formula for rate of reaction
=> changes in the reactant / time taken for the experiment - chemical reactions happen at different times
- high / low rates
Factors affecting rate of reaction
- Temperature
- Concentration (volume)
- Surface Area
- Catalyst
Graph
x axis = independent
y axis = dependent
Collision theory
- rate of reaction
- must collide
- right amount of energy
Concentration
more particles in the same space => more collision => more effective collision
Temperature
- particles turn heat energy into kinetic energy
- hotter => move faster => more collision => more effective collision
Activation Energy
- minimum amount of energy needed to start a reaction
Surface Area
- reactions involving a solid = takes place on the surface
- decreasing the size of a reactant = more surface area is exposed
- smaller the pieces, the larger the surface area
- more area => more collisions => more effective collisions
Experiment:
- powder will produce faster because there is more surface area
Catalyst
- substances that change the rate of reactions, without being used up in the reaction
- produce the same amount more quickly, never produce more product
- catalysts lower the activation energy of a reaction
- presence of catalysts => activation energy is lower => more collisions => more effective collision
Properties of catalysts
- speeds up the rate of reaction
- not used up in a reaction
- can be removed and used in another experiment
- only a small amount is needed in a reaction
Importance of catalysts
- products can be made more quickly, saving time & money
- catalysts reduce the need for high temperature, saving fuel and reducing pollution
Exothermic
- give out energy
- the temperature will increase
- the end is below the activation energy (graph)
- more energy is RELEASED that SUPPLIED
Endothermic
- take in energy
- the temperature will decrease
- the end is above the activation energy (graph)
- more energy SUPPLIED than RELEASED
Chemical energy
- stored in substances
- released through a chemical reaction
e.g. fuel, battery, food, firecracker
Fuel Value
- amount of heat released when 1g of a fuel is burned
- fuel value = heat released/mass of fuel
- higher the fuel value the more energy it has
Fire triangle
- fuel
- oxygen
- heat
Combustion
- chemical reaction
- takes place when substance burns
- reacts with oxygen
- energy is released as heat and light
Oxidation
reaction with combustion and oxygen
Complete Combustion
- carbon reacts with oxygen, completely
- carbon + oxygen –> carbon dioxide
Incomplete Combustion
- carbon reacts with oxygen, incompletely
- carbon + oxygen –> carbon monoxide
