Module 1 - Development of Practical Skills Practical Skills Flashcards
Module 1
What is the main way to increase accuracy?
Take 3 repeat meanings and calculate mean
What reduces RANDOM error
More sensitive equipment to reduce uncertainty (eg smaller graduations)
What reduces SYSTEMATIC error
Calibrating equipment
How to work out uncertainty: analogue vs digital
Analogue: 1/2 smallest graduation
Digital: the resolution
When measurement gets smaller, does % uncertainty get bigger or smaller?
Bigger
% uncertainty formula
(Uncertainty/og measurement) x 100
When you take 2 readings (eg length, temp) what is the % uncertainty formula?
(2 x uncertainty / quantity measured) x 100
Why is systematic error more problematic?
•affects all results
•dont realise
•affects mean
Light microscope’s vs electron microscope’s resolution
Light: 200nm
Electron: 0.1nm
Why do electron microscopes have a higher resolution?
Electrons have shorter wavelengths than light so there’s less diffraction (overlapping)
2 scales on the light microscope and where are they?
Stage micrometer (stage)
Eyepiece graticule (slide)
1 division on the stage micrometer=…
10 micrometres
Reducing sugar test (2) (why is it semi-qualitative?)
Benedict’s reagent is added and the sample is heated
Pos: green, yellow, orange, red
Semi qualitative bc the warmer the colour, the ^^ the concn
Non reducing sugar test (2)
Hydrochloric acid is added (to hydrolyze any non-reducing sugars)
Benedict’s reagent is added
Pos: brick red precipitate
What is a reducing sugar? What substances are reducing/non reducing?
A sugar that reduces another chemical (donates e-)
Reducing: all monosaccharides, lactose and maltose
Non reducing: most disaccharides, eg sucrose
Lipid test (2)
Ethanol is added (to dissolve lipids so they aren’t visible)
Water is added (to form micelles which diffract light)
Pos: emulsion forms (a fine dispersion of droplets)
Protein test (2)
Sodium hydroxide is added
Hydrated copper (II) sulfate is added
Pos: lilac (due to copper (II) forming bonds w peptide bonds)
