Practical skills 1: safety
The use of which apparatus requires hair to be tied and goggles to be worn?
The Bunsen burner.
Which apparatus can be used to quickly and simply measure a volume, but is less accurate than a burette?
The measuring cylinder.
What is the name given to the type of data that can be measured?
Quantitative data.
What is most commonly used to record observations in chemistry?
A table
Use a measuring cylinder or a burette instead.
What is the name given to any chemical substance capable of causing harm to a person or the environment?
A chemical hazard
What is the name given to the variable you manipulate or vary in an experimental study to explore its effects?
The independent variable.
Give an example of qualitative data.
A colour change, the formation of a precipitate, smell...
On which axis of a graph, should the values of the independent variable be located?
The x-axis.
During titration, the end-point is usually identified through a change in colour. This is however a source of human error, why?
Because each individual perceives colour slightly differently, which affects the outcome of the experiment.
Which hazard symbol is represented by red triangle/diamond surrounding a skull?
Toxic/poison hazard.
If you want to estimate the concentration of a NaOH solution, using a solution of H2SO4 of known concentration, what type of experiment would you carry out?
A titration.
What can be done to spot and discard anomalous readings?
Taking repeated measurements.
In a graph, what is an ''outlier''?
It is a data point that doesn't fit the pattern shown by the other points on the graph.
In exam, when asked about ways to improve an experiment what can be a standard answer?
Repeat the experiment AND calculate the mean.
What should you be careful about when collecting a gas in a sealed container?
The container used for the collection of gas must be big enough for the amount of product that will be released, otherwise it may burst and damage the equipment.
What is the difference between precision and accuracy?
Precisions: how close to each other are repeated measurements.
Accuracy: how close a measurement is to the real value.
When carrying out a titration, what is the name given to the very first trial (1st titration), which aims to estimate the end-point?
The rough titration.
In exam, what should you do if you are asked to draw a ''line of best fit'' and the data points on your graph are not perfectly aligned?
A freehand continuous curve must be drawn. Never just connect the points like a ''dot-to-dot''.
In general, at least how many times should an experiment be repeated? and how many different values of independent variable should be investigated?
The experiment should be repeated at least 3 times (or 3 readings), and 5 different values of independent variable should be investigated at least.
If you spill a strong corrosive substance on a surface it is advised to neutralize it first with sodium bicarbonate; however, if the spill is on your skin, it is advised to wash it thoroughly with water. Why?
Because acid-base reactions are typically exothermic, which would increase the damage done to your skin.
Which apparatus uses vacuum to quickly carry out a filtration?
the Büchner Flask (+ Büchner funnel)
When taking readings from an apparatus filled with liquid, you must take the measurement from the bottom of the curve of the liquid. What is it called?
The meniscus.
What is the formula to calculate the slope of a graph?
slope = rise/run = (Y2 - Y1)/(X2 - X1)
A student is asked to use a mass balance to measure the mass of NaHCO3 contained in a stoppered container, as it will be used in an experiment. How should the student proceed?
First measure the mass of the container with NaHCO3 still inside.
Then measure the mass of the empty container.
Finally calculate the difference between the 2 masses, to know the mass of NaHCO3 used.