science skills
accuracy: a measurement that is close to the true value
valid: the suitability of the investigative procedure to answer the question being asked. linked to control variables
precision: precise measurements are ones in which there is very little spread about the mean value
repeatable: if the original person repeats the investigation using the same method and equipment and gets the same results
reproducible: if the investigation is repeated by another person, or using different equipment or techniques, and the same results are obtained
anomalies: values in a set of results which are judged not to fit the pattern - or be significantly different
discontinuous data: values that are labels, eg names of plants, or types of material
continuous data: have values that can be given a number by counting (ex: number of shrimp) or by measurement (eg light intensity, or time)
independent variable: the variable you change in an investigation
dependent variable: the variable that you measure in an investigation
control variables: the variables that are kept the same in an investigation as they may affect the outcome of the experiment
INVESTIGATION 1:
To investigate how the length of a nichrome wire affects the resistance in a circuit
method (simplified): connect the nichrome wire to a meter ruler with crocodile clips and decrease the distances of the crocodile clips and measure the resistance every time you decrease it.
safety precautions: you need a fixed resistor within the circuit because the shorter the wire, the hotter it becomes. this could cause fires or burns.
conclusion: results show that the length of the wire and the resistance are directly proportional - as the length of wire decreases, the resistance decreases as well.
independent variable: length of the wire
dependent variable: resistance
control variable: the current
INVESTIGATION 2:
Investigate how the number of turns in a coil affects the strength of an electromagnet
method (simplified): turn the coil around a nail and then try to pick up as many paperclips as you can. increase the number of turns on the coil and pick up as many paperclips as you can, and keep increasing the number of turns and record how many paperclips you pick up each time.
safety precautions: do not handle the wire, switch off between readings and do not set up the experiment near taps, sinks, etc.
conclusion: as the number of turns in the coil increases, the number of paper clips picked up increases
independent variables: the number of turns on the coil, the range of the number of coils
dependent variable: number of paperclips picked up
control variables: the size of paperclips, the current, the voltage, and the nail
INVESTIGATION 3:
Find out how some variables affect the speed of a car
method (simplified): release a toy car from the top of a ramp - a ramp which you have measured the height and distance of - and time how long it takes to reach the bottom. change the height of the ramp and measure the time it takes to reach the bottom.
safety precautions: stand away from where the car is headed to avoid getting hit, also move any easily breakable objects.
conclusion: as the height of the ramp increases, the speed increases and the time decreases.
independent variables: the height of the ramp, the time, the speed
dependent variables: the speed, and time taken
control variables: the size of the toy car, the material of the ramp, the distance of the ramp
INVESTIGATION 4:
To investigate how the characteristics of a falling asteroid affects the size of the crater formed
method (simplified): drop different-weighted ball bearings into a box of sand from the same height, and measure the width of the crater they make.
safety precautions: always drop the ball bearings into the sand and avoid dropping it on your feet, or hands
conclusion: as the mass of the ball bearings increased, so did the width of the crater
independent variable: the mass of the ball bearings,
dependent variables: the width of the crater
control variables: the height, the amount of sand in the box
INVESTIGATION 5 & 6:
Investigate changes in mass when copper carbonate and magnesium are heated
method (simplified): add copper carbonate to a boiling tube clamped at an angle heated over a bunsen burner and stop heating when it changes colour. let it cool and find the mass of the copper carbonate by subtracting the mass of the boiling tube from the final mass.
safety precautions: wear goggles, make sure that the boiling tube is not pointing to anyone else, wash your hands afterwards
conclusion: the mass of the product should be less than that of the reactants because the gases (copper oxide and carbon dioxide) escaped
independent variable: the temperature of the copper carbonate
dependent variable: the mass of the copper carbonate
control variables: the mass of the boiling tube
Investigate changes in mass when copper carbonate and magnesium are heated
method (simplified): place a magnesium ribbon in a crucible over a bunsen burner and take off the heat when you see further reactions from lifting up the crucible lid a little. let it cool and compare the mass of the magnesium, crucible, and lid before and after heating.
safety precautions: use tongs to move the crucible to a heatproof mat, don’t look directly at the magnesium for a while because it is very bright.
conclusion: the mass of the magnesium increases because the oxygen has mixed with and reacted with the magnesium
independent variable: the mass of the contents of the crucible
dependent variable: the mass of the contents of the crucible
control variables: the mass of the crucible and lid
INVESTIGATION 7:
Test the hypothesis that the volume of carbon dioxide produced by respiring yeast depends on temperature
method (simplified): add sugar, yeast, and bread flour together and stir in water for a smooth paste in a beaker, split them into three and place them in places of different temperature. after 30 minutes record the new volume of dough in each measuring cylinder.
safety precautions: do not eat any dough, wear goggles
conclusion: if the temperature increases then the volume of the dough also increases
independent variable: the temperatures in which the measuring cylinders were placed
dependent variable: the volume of the dough
control variable: the starting volume
INVESTIGATION 8:
To investigate the most effective shape for wind dispersal used by sycamore seedlings
method (simplified): drop different shapes of sycamore seedlings from the same height and compare the time they take to drop.
safety precautions: be careful when using the meter ruler
conclusion: seed 4 was the most effective seedling because it stayed in the air the longest
independent variables: the width of the seeds, the thickness of the seeds, the length of the seeds
dependent variables: how long the seed stays in the air
control variables: the height the seeds are dropped from, the mass of the paper
measuring liquids:
millilitres
measuring cylinder
measuring mass of a solid:
balance
g/kg
measuring the current through a circuit:
ammeter
amps
measuring time:
stopwatch
second(s)