Do Now: Exam Question
• Complete the exam question on the sheets
provided.
• 10 minutes to answer the question (10 marks)
• 10 minutes to mark your answers.
Emulsions
To be able to:
Recall how emulsifying agents can help oil and
water mixtures to remain mixed (B/A)
Give two uses of emulsions (C)
Plot a graph or bar chart appropriate to the data
collected (HSW B)
Picture to words:
• Recall how emulsifying agents can help oil and water mixtures to
remain mixed (B/A)
• Try to explain what is happening in each of these
two pictures:
Think
Pair
Share
Key Words
Dense
Float
Polar/ionic
Non Polar/covalent/
hydrocarbon
Immiscible
Picture to words:
• Recall how emulsifying agents can help oil and water mixtures to
remain mixed (B/A)
Use the grid below to give yourself a grade for your responses.
Statements
The oils floats on top of the water
This is because the oils and the water don’t mix
The oil is less dense than the water so it floats
The oil and the water are immiscible
The oil is a hydrocarbon
The water is a polar/ionic substance
The water and oil are immiscible because the polar
molecules in the water repel the non polar molecules
of the hydrocarbon (oil)
Grade
C
B
A
A*
Emulsions
• Give two uses of emulsions (C)
• What if we want the oil and water mixture to
remain mixed?
• We need to use an EMULSIFIER.
Exam Tip: You need to be able to name
at least two common emulsions.
Here are three!
Practical
• Plot a graph or bar chart appropriate to the data collected (HSW B)
• You are going to investigate the action of different
emulsifiers.
• You must wear goggles.
• Follow the instructions carefully to record your
results.
• When you have finished complete Q1-4 of the
analysis then plot your graph. Plot the most
appropriate graph/chart for your results.
– There is a help sheet available for this – ask if you need a
copy.
Emulsifiers – the SCIENCE
• Recall how emulsifying agents can help oil and water mixtures to
remain mixed (B/A)
• Emulsifiers are special substances that prevent oil
and water mixtures from separating.
• They do this because of their structure.
Emulsifiers – The Science
• Recall how emulsifying agents can help oil and water mixtures to
remain mixed (B/A)
Water is a polar molecule...
• .
• It’s really simple...
It has covalent (electron sharing)
bonds between the hydrogen and
oxygen atoms.
The oxygen atom has a really strong
pull from it’s nucleus (8 protons).
This pull causes the electrons in the
covalent bond to be pulled towards
the oxygen atom.
Overall this shifts the balance of charge...
There are more negative charges (or electrons) near to the
oxygen atom – so this becomes overall slightly more negative.
The hydrogens are left with only a proton so they become slightly
more positive.
Emulsifiers – The Science
• Recall how emulsifying agents can help oil and water mixtures to
remain mixed (B/A)
• Oils on the other hand are long chains of hydrocarbon
molecules.
• All carbons and hydrogens covalently bonded...
• Because there is no oxygen then there are no polar
WARNING: Other atoms like N, F, Cl, Br and I make molecules polar
molecules.
as well
• This is the reason why oils and water don’t mix...
• Like substances dissolve in like
– Salt (an ionic or charged compound) will dissolve in polar liquids
like water but not in non polar liquids like oils.
– Oils and water don’t mix because water is polar and oils are non
polar.
Emulsifiers – The Science
• Recall how emulsifying agents can help oil and water mixtures to
remain mixed (B/A)
• So... Non polar
hydrocarbons, e.g.
Oils, will separate
from polar liquids
like water.
• Enter the
emulsifier...
• Remember the
hydrophilic (polar)
head and the
hydrophobic (nonpolar) tail...
The opposite is true for a W/O
type emulsion.
The hydrophobic tails help to
suspend the droplet in the oil.
• In an O/W type
emulsion, the
hydrophobic tail
embeds itself into the
oil droplet.
• The hydrophilic head
pokes out into the
water.
• The water and the
polar head are
attracted to each
other.
• This stops the oil
droplet from floating
up to the surface of
the water.
Emulsions Exam Question
• Test yourself:
1. Try to complete the exam question from your
memory of your note.
2. Use your notes to help you, but now write in a
different colour (NOT RED)
3. Mark the exam question using the mark scheme,
this time in red and add corrections.
The more red pen there is = the more revision you
have to do at home.
Homework
• Check the weebly for your homework:
1. If you did not finish the graph or analysis questions
you must do so
2. Download, print and complete the homework
sheet on emulsions.
All of the homework is due to me next lesson.
E
Graph drawing Support
• Explain the difference between discreet and continuous data.
•
•
•
•
•
There is a link between the type of emulsifier used and the
amount of time taken for the mixture to separate.
What is the independent variable for this investigation?
Does your independent variable have a range of values? (does it have
numbers?)
Could you select a value that is in the middle of the independent
variable and suggest an value for the dependent variable?
If there is no range of numbers for your independent variable, what
kind of variable is it, discreet or continuous?
What kind of graph or chart should you draw form this data?
– Think about the type of graph that you could draw, if there are no values
between the intervals for the independent variable does this suggest a line
graph or bar chart?
ISA Graph Marking Criteria
• Plot a graph or bar chart appropriate to the data collected (HSW B)