Spring Term A Flashcards
(26 cards)
Define diffusion.
The net movement of particles from a region of high concentration to a region of lower concentration down a concentration gradient.
Does a concentrated solution have a low or a high water potential?
A low (negative) water potential.
How do you calculate percentage change?
Difference divided by original multiplied by 100.
How do you calculate the rate?
Divide the measured dependent variable by time.
How do you calculate the surface area:volume ratio?
Divide the surface area by the volume.
How does a bar chart differ from an histogram?
In a bar chart there are gaps between the bars because they represent categorical or discrete variables, whereas in a histogram the variable is continuous and the bars touch.
In an experiment, which is the dependent variable?
The variable which you are measuring.
In an experiment, which is the independent variable?
The variable which you are changing.
State four factors that affect the rate of diffusion.
Concentration gradient; temperature; surface area or surface area:volume ratio; distance.
State two differences between diffusion and active transport.
Active transport uses energy; active transport is against a concentration gradient.
State two differences between diffusion and osmosis.
Osmosis is the movement of water molecules; osmosis is movement across a partially permeable membrane.
What is a hypothesis?
A hypothesis is a statement about nature that can be tested by experiments or by new observations.
What is a water potential gradient?
A difference in water potential either side of a partially permeable membrane.
What is an accurate experiment?
One in which your results are close to the true underlying results that you are trying to measure.
What is an anomalous result?
A data point that does not fit the pattern or the trend of other data points.
What is meant by the term ‘partially permeable membrane’?
Some molecules are able to pass across the membrane but others cannot.
What is the difference between osmosis and diffusion?
Osmosis is the movement of water molecules across a partially-permeable membrane.
What is the rule about presenting data in a table?
Units are only written in the column heading, never in the cells of the table.
What is turgor pressure?
the pressure exerted by the cytoplasm of a cell against a cell wall.
What is water potential?
A measure of the number of free water molecules in a solution.
When drawing a graph, what are the key (marking) points?
SCALE: linear and uses at least half the graph paper provided; LINE drawn straight, neat and through points, dot to dot with a ruler; AXES labelled with the variable and the units; POINTS plotted correctly; KEY (if necessary) clearly label each line if more than one line is drawn - don’t use different coloured lines
Why do you control variables in an experiment?
To ensure that the experiment is a fair test of the variable under investigation. It ensures that only the variable you are investigating is changed.
Why do you repeat an experiment?
To make it more reliable; to identify anomalous results; to enable you to calculate a mean.
