rates of reactions + atoms Flashcards
Define variables
Something that can be changed in a chemical reaction
Examples of variables?
Temprano
Particle size
Concentration
Volume
Mass
What is a fair test?
In order to determine what factor is affecting a chemical reaction you must only change one variable at a time.
How do you carry out a fair test?
If you only change one variable at a time then you are carrying out a fair test
What do large particles result in
A slow reaction
What do small particles result in
a fast reaction
What does low concentration result in
a slow reaction
What does high concentration result in
a fast reaction
What does low temperature result in
A slow reaction
What does high temperature result in
A fast reaction
What is the effect of particle size on a reaction
As particle size decreases - surface area increases - area available for collision increases.
What is the effect of concentration on a reaction
Increasing the concentration of reactants- increases the number of collisions
What is the effect of temperature on a reaction
As the temperature increases-amount of energy a particle has increases-the faster a particle moves around-more likely particles are to collide-rate of reaction increases
What is the effect of a catalyst on a reaction
A substance that speeds up the rate but can be recovered chemically once reaction has given to completion
Explain collision theory?
For a chemical reaction to occur the reactant particles must collide this provides the energy to break the bonds in the reactants and from new ones in the product
Explain Successful collisions
Not all collisions result in chemical reactions those that do are successful in order for this to happen the must collide with the sufficient energy and correct geometry.
What do all chemical reactions produce
New substances
How can the speed of reaction be found?
By measuring how fast the new substance is formed
What happens at the A part of the graph(longer sorta straighter bit )
Reaction is at its fastest/concentration of reactants is highest
What happens at point B of the graph (still going higher but becoming steeper in middle of graph small)
Reaction is decreasing/reactants being used up
What happens at pint C on graph(part of line is now horizontal)
Reaction is finished (gone to completion) all reactants have been used up+converted to products
Reading Particle size on graph
If particle size is increasing the slope is less steep and plataeu has no change if it is decreasing slope is steeper and plateau also no change
Reading concentration on Graph
If it is increasing the slope is steeper and plateau is higher, if it is decreasing the slope is also steeper but plateau is lower
Reading temperature of graph
If it is increasing the slope is steeper and plateau no change, if it is decreasing slope is less steep but plateau also no change
Reading the use of catalyst/enzyme on graph
Slope is steeper but plateau no change
Reading an increase in mass/volume of graph
The slope is unchanged but plateau is higher
What do you need to calculate average rate?
The initial + final quantities and the time interval
What is the formula for finding average rate
🔺quantity / 🔺 t
What is delta 🔺
Change in
What units are used in average rate calculations
Cm s-1 or cm3/s NOT cm3/s-1
Describe periodic table
Everything in the world is made up of 118 elements that scientists have classified in to the periodic table and into groups of similar chemical properties
Describe the properties of group 1 - Alkali metals
Very reactive
Stored under oil
Soft (can be cut with a knife)
React with water to form an alkaline solution
React with oxygen to form metal oxides
Describe the properties of groups 2&3 the transition metals
Hard and dense
Less reactive than the alkali metals
Used in catalysts
Form coloured compounds
Describe group 7 the halogens properties
Diatomic elements
All toxic
Florine added to toothpaste to prevent decay
Chlorine added to swimming pools to sterilise
Iodine used to treat wounds
Describe the properties of group 8 the noble gases
Least reactive of all elements
Do not react
What are elements made up of
Only one type of atom
What are atoms made up of?
3 different elementary particles; protons electrons and neutrons
Describe the nucleus
The centre of the atom contains the protons and neutrons +charge
Describe protons
+charged found in the nucleus RAM=1
Describe electrons
-charged found orbiting the nucleus RAM=almost zero
Describe neutrons
neutral charge located in the nucleus RAM = 1
Explain why atoms are neutral
Because the number of positively charged protons are equal to the neagativley charged electrons
Also note that the neagative electrons orbit around the positive protons, opposites attract
What do elements have associated with them?
A symbol and 2 numbers
what is the mass number and where is it written
The number of protons and neutrons, it is to the left of the symbol on the top
what is the atomic number and and where is it written?
The number of protons/electrons it is erigen on the left of the symbol on the bottom
How is the number of of neutrons calculated?
Mass no. - atomic no.
Define isotopes
Atoms that are of the same element and have the same atomic number but different mass number
What do isotopes have?
The same chemical properties i.e. all the isotopes of of hydrogen have the same chemical behaviour
