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hypothesis
an idea that you can test using practical experiment
key features of a hypothesis
- be able to be tested scientifically
- relate one dependent variable to an independent variable
null hypothesis
states that there is no relationship between the variables
e.g no relation between the temperature and the rate of reaction
qualitative data
it refers to the appearance or value of something
e.g the colour observed or bubbles being produced
quantitative data
numerical measurements made such as volume or time
SOP
- standard operating procedure
- an established procedure or method used to carry out a routine activity which ensures consistent results everytime
examples of SOPs
Titration handling of chemicals , disposal of waste , qualitative analytical test, preparing solutions
risk assessments
it identifies hazards, evaluates the risks associated with those hazards and it determines ways to eliminate or control those risks
hazard
when the equipment or substance can cause harm
e.g hot plate
risk
the harm that the hazard could cause and chances of it happening
e.g the risk of getting burnt by a hot plate
independent variable
the variables that are changed in an investigation
dependent variable
the variables you are investigating and measure during an investigation
control variables
the variable you keep constant during an investigation
method
a step-by-step set of instructions
be logically ordered
allows you to take sensible measurements and allows you to test your hypothesis
what is needed in a method
that it will produce a range of results, reliable results, precise result and accurate results
types of data
- continuous data - age of plant, number of pants
- mixture of data - numbers and names e.g different types of plants
bar chart - data
- continuous data - smooth curve of best fit
- curve goes through or near most points
bar charts - use
- used for discrete data
- can be used to compare different sets of data
pattern on graph
- the shape of the graph
- line that goes up as time goes by
trend on graph
- the relationship between factors on the graph or table
- full trend - volume that increases as the time increases but then levels off a certain amount of time
sample size
- the number of people/objects used as a sample in the investigation
- large sample size - strong evidence = confident investigation
primary data
- data that has been gathered yourself through experiments or investigations
secondary data
- the data that you get in books, specific papers or the into
- compare the primary data and secondary data to draw a conclusion
identifying anomalous data
- it doesn't fit the pattern of other results
- it does not lie close to the line of best fit
causes of anomalous data
- not following the method properly
- inaccurate measuring / recording
- impurities
systematic error
- an error that always occurs in the same direction
- can be corrected by calibrating the balance - quantitative errors
random error
- due to not following the method correctly
- can be minimised by repeating results and taking averages
misreading observations
- can cause qualitative errors
accuracy
- how close the data is to its true value
- e.g - errors due to the equipment - less accurate
reliability
- how trustworthy the data is
- usually insured by repeating the findings to identify anomalous data
precision
- how close the repeat readings are to each other
- can be improved by using measuring equipment that has more decimal places
what is an enzyme
a protein molecule that acts as an catalyst in a chemical reaction
proteins
made up of amino acids
4 chemical groups attached to the central carbon
- hydrogen atom
- amino acid
- carboxyl
- variable R
r groups
- 20 different R groups
- means there are 20 different amino acids
amino acid links
linked together by two peptide bonds
condensation reaction
occurs between two amino acids
produced by condensation reaction
water
formation of a dipeptide
formed by two amino acids linked by a peptide bond
tripeptide
formation of three amino acids
polypeptide
formation of many amino acids
protein
polypeptide with more than 50 amino acids
active site
the part of an enzyme where the biochemical reaction takes place
secondary structure
where polypeptide chains form orderly shapes
secondary structures shape
held in place by hydrogen bonds between the NH of one of the peptide links and the -C=0 of another amino acid
tertiary structure
a three dimensional shape of a secondary structure
what does the tertiary structure give?
- gives the enzyme the shape of the active site
most common shapes of secondary structures
- coiled α-helix
- folded -pleated sheet
active site
- consists of a small number of amino acids which form a specific shape due to the proteins secondary and tertiary structure
enzyme catalysing a reaction
- takes place on the active site of an enzyme
function of enzymes
to catalyse one type of biochemical reaction
conversion of substrates
- biochemical reaction
- converted into products
binding of substrate
- binds to active site
- only specific substrates will bind to a particular enzymes site
what happens after a biological reaction
- the product is released
-active site is available to catalyse further reactions
what happens to the active site if the temperature is too high
- if the temperature too high, the hydrogen bond will break
- means the enzyme changes its shape - active site looses its shape
- denatured enzyme- no longer act as a catalyst
catalyst
-a substance that speeds up a reaction
- can take part in the reaction but it is left unchanged at the end of the reaction
what catalysts are enzymes
biological catalyst
Collison theory
- for a reaction to occur the particles must collide and the particles must have enough energy to react
what does the energy of the collision depend on
speed of the particle and the angle which they collide
activation energy
the minimum energy needed for the particles to react
why does the enzyme lower the activation energy needed
if there are more particles they have more of the required energy to react
- this means there are more successful collisions and faster reactions
catalytic energy
the increase in the rate of a reaction caused by the inclusion of an enzyme
substrate
the molecule that is effected by the activation of an enzyme
active site
the area of the enzyme where a substrate binds
denatured
when the teritiary structure of an enzyme is changed
how can enzyme reactions be measured
-by measuring a decrease in the substance
- measuring increase in product
- measuring an increase in product is easier because you will know the starting rate will be 0
why must the initial rate of reaction be recorded
as the rate will decrease as the substrate is used up and its concentration decreases
what does the enzyme need in order to work effectively
specific conditions
- temperature
- pH
- concentration of enzyme
what happens if the specific conditions are not present
the enzyme catalysed reaction may slay down or not work
optimum tempreture
- each enzyme has this where it works the fastest
what happens as the temperature increases to the optimum temperature
- the reaction rate also increases
what happens below the optimum temperature
there is less energy which means there are fewer collisions - slower reaction
what happens above the optimum temperature
-the hydrogen bonds in the enzyme break
- the active site loses its shape and therefore there are no catalysts
how does pH affect the active site
- affects the charge
- if the pH changes the charges on the active site will change and the substrate will no longer be able to bind to it
what does the concentration of the enzyme and the substrate effect
the rate of reaction
what happens if the concentration of the substrate is too high
- there will be no more active sites for them to bind to
- increasing the concentration of the substrate further than this will no longer affect the rate of reaction
what happens if the concentration of the enzyme is too high
- there are too many available site compared to the substrate molecules - the rate of reaction will no longer increase
diffusion
the movement of substances from a region of high to low concentration
what can diffusion occur across
- a membrane
- as long as the molecules are small enough to pass through the membrane then diffusion will occur
factors affecting the rate of diffusion
- size
- temperature
- distance through the substance
- surface area
- shape of the surface of which the molecule is diffusing
how does size affect the rate of diffusion
the larger molecules move more slowly than the smaller one so the rate of diffusion decreases
how does temperature affect the rate of diffusion
a higher temperature increases the energy molecules have which causes them to move faster - increases the rate of diffusion
how does distance affect the rate of diffusion
the greater distance that the molecules must travel through a substance, the slower the rate of diffusion
how does surface area affect the rate of diffusion
as surface area increases the area of which molecules can spread is increased
- the rate of diffusion increaes
how does the shape affect the rate of diffusion
the shape of the surface of which the molecule is diffusing can affect the rate of diffusion
kinetic theory
- explains the properties of different states of matter and diffusion
arrangement of particles in a solid
close together in a regular pattern
arrangement of particles in a liquid
close together in a random pattern
arrangement of particles in gas
far apart and in a random arrangement
properties of solids
- in a fixed shape and they cannot flow
- cant be compressed
properties of liquids
- take the shape of a container
- flow and move randomly
- cannot be compressed or squashed
properties of gases
- completely fill container
- can flow and move randomly
- they can be compressed or squashed
where can diffusion happen within
- mixture of liquids
- mixture of gases
- mixture of both
how do humans improve the growth of crops
- they correct soil pH
- optimum watering
- correcting nutrients present
negative effects human have on plant growth
- trampling
- picking wildflowers
- removing hedges and trees
human effect on the distribution of plants
- sowing crops means certain fields only have one type of plant
- trampling can cause unusual or more widespread distribution patterns due to seeds being carried on the bottom of shoes
what pH do plants grow best at
between 4.5 and 7.5
acidic soil
high deficiency in necessary minerals such as iron and manganese
why is soil aeration necessary
it allows sufficient oxygen to get to the plant and for carbon dioxide to be removed
what forms when there is little aeration
toxins form e.g. hydrogen sulphide gas
