unit 3 -applied science

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