Pracs pt 1 Flashcards
What are reducing sugars?
Sugars that can donate an electron to another molecule
What sugars are reducing sugars?
All monosaccharides an some disaccharides (e.g. Maltose & Lactose)
Give examples of monosaccharides 3
glucose, fructose and galactose
give examples of disaccharides 3
Maltose, sucrose and lactose
How do you test for reducing sugars? 3
Place 3cm^3 of food solution into boiling tube & 3cm^3 of Benedict’s solution
Place boiling tube into beaker of boiling water
It will go from blue to warmer colour if reducing sugar is present
How to test for non-reducing sugars? 7
Add 3cm^3 of food solution into boiling tube
Add 3cm^3 of dilute hydrochloric acid
Gently boil the solution for 5 minutes
Add 3cm^3 of a dilute alkali like sodium hydroxide solution
Use pH paper to check if solution is alkaline
Add 3cm^3 Benedict’s solution and heat in boiling water for 5 minutes
Positive test will show warmer colour change
When would you test for non-reducing sugar?
When there is either no reducing sugar or a very small amount
What do you use to test for starch?
Iodine solution
How do you test for starch? 2
Add drop of iodine to food sample
Solution will turn blue/black if starch is present
What do you use to test for proteins?2
Biuret solution, which contains copper(II) sulfate and sodium hydroxide
How do you test for proteins? 3
Add drops of sodium hydroxide to each sample
Add drops of copper(II) sulfate solution to each sample
Colour change from blue to lilac if protein present
Draw a table of a simple dilution. You are given 1% concentration of HCL solution, make 5 concentrations of this solution, each with a volume of 10cm^3
On layer
Draw a diagram of the simple dilution you made a table of
On Layer
Draw a diagram of a serial dilution of 1% HCL solution, reducing by a factor of 10 each time
On LAyer
Draw a diagram of a serial dilution of 1% HCL solution, reducing by a half each time
On layer
What are the main steps in drawing results tables? 4
Units are only in the headings
Independent variable comes first in the table
All results are recorded with the same number of decimal places
Values calculated for mean are recorded to same precision as raw data
What are the main steps in drawing line graphs? 4
Independent variable is on X axis, dependent on Y
The scale along each axis must be spaced at equal intervals
Scales should cover full range of data plotted on graph
Points should be plotted as crosses, NOT dots
What are the main points for a line of best fit? 4
Can be smooth, free hand curve OR a straight line drawn with a ruler
Should intersect majority of points
Should have equal number of points on either side of the line
Never continue the line beyond the final point unless asked
What do examiners mean when they say “Plot a graph” vs “plot a chart”
Graph= line graph
Chart= Bar chart
