Titration/practicals Flashcards
Suggest why a stopper needs to be put in the conical flask as quickly as possible-
To reduce the escape of the gas
Explain the method of titration- 6 marker
Use a pipette and pipette filler to take 25cm3 sodium hydroxide ( it depends what acid they give u, say depending on the acid mentioned)and place it into a conical flask.
Place the conical flask on a white tile and the tip of the burette needs to be inside the conical flask.
Fill the burette with sodium hydroxide and record the intital volume.
Place a few drops of a suitable indicator inside the solution in the flask. (Such as methyl orange which turns from red to yellow, and phenolphthalein turns from colourless to pink)
Perform rough titration and take burette readings, and swirl the flask vigorously.
Quickly close the tap if you were to observe a sharp colour change and record the volume in which the colour changes at eye level to avoid parallax error.
repeat the titration at least 3 times with a fresh batch of sodium hydroxide.
What is parallax error?
Not reading the measurements at eye level
How do you calculate uncertainty?
Range/ 2
Range - biggest number- smallest number
State the types of errors in investigations-
Calibration- making a scale on a measuring instrument. Rechecking your answer to see if you got it right or not. ( placing a thermometer into melting ice to see if it’s zero since ice melts at 0 degrees.)
Types of errors-
Measurement error- the difference between a measured value and a true value. Ex- MV: 22 and the TV: 21.5 (there is a half inch off) systematic error and random falls under this.
Systematic error- error done by the instrument ( equipment),
What will it cause? The results to differ by the SAME AMOUNT each time, since it’s a system not a human being.
How to reduce the effect? Use a different set of equipment, compare your results.
Random error- made by the person doing the experiment, can be due to incorrect timing, reading the instrument incorrectly, parallax error.
What will it cause? It will cause the results to differ by DIFFERENT amounts each time.
How to reduce it? Make more measurements to spot something you have missed, calculating a new mean.
Zero error- when an equipment cannot read zero, causing a slight increase of mass in whatever you’re measuring.
Anomalies- set of values that are not counted in the results due to random uncertainty.
State the most important keywords that keep being brought up in exams-
Fair test- when the independent variable is allowed to affect the dependent variable. The effect of exercise (IV) on heart rate (DV)
Hypothesis- intended to explain certain facts and observations.
Interval- quantity between readings. 6<x<11 x: is the quantity between readings.
Precision- how close the measurements are to eachother, the closer they are, the more precise the results.
Reproducible- when an experiment is done by another person, using different techniques and equipment and still obtain the same results as the original experiment: this is how we know an experiment is reproducible.
Resolution- commonly asked as what is the thermometers resolution. First of all see how the numbers increase, if it was by 1 (1,2,3,4,5,6,7..etc) then the resolution will be 1.
Categoric variable- variable that has labels. Names, types of material,etc
Continuous variable- a random variable (temp, energy, speed) that can take up an infinite number of values.
