CHEMISTRY
Lab Activity: MIxTuREs
Getting Ready:
In this lab activity, you will examine six different water-containing mixtures and classify each as
a suspension, a co/bid, or a solution. You will filter each sample and look for the Tyndall effect
in both the filtered and unfiltered samples. Particles in a suspension can be separated by
filtration, while those in a colloid or a solution are too small to be retained by the filter paper.
The Tvndall effect will reveal the presence of colloidal particles.
Complete the pre-lab in your lab journal. An example of what your data tables should look like
is shown below. Be sure to make your data tables large enough so that you can easily record
your observations.
Sample Data Tables:
Sample
Color
Clarity
Original Samples
Settle Out? Tyndall Effect
Classification
A
B
C
D
E
F
Samp Color
A
B
C
Clarity
Settle Out?
Filtrates
Tyndall Effect
Left on Filter Paper?
Classification
Dl
El
F]
Procedure:
1. Put on your goggles and aprons.
2. Carefully examine each of the mixtures in the vials. Record your observations in your
“Original Samples” data table.
•
•
What color is the mixture?
Is the mixture clear or cloudy?
•
Are any particles settling out?
•
Perform the Tynd all effect test by shining the laser beam through the liquid. Can you
see the light beam in the liquid (if yes, then positive for Tyndall effect; if no, then
negative for Tyndall effect).
3. Set up your ring stand with a small iron ring and funnel. Place a ioo-mL beaker
underneath the funnel. Fold a piece of filter paper and place it in the funnel. Moisten
the filter paper with a little water so that it adheres to the side of the funnel.
4. Your teacher will give you one of the six samples to filter. Measure 25 rnL of your sample
in a graduated cylinder and slowly pour this sample into the filter. Carefully examine the
filtrate (the liquid now in the beaker) and record your observations in your “Filtrates”
data table.
What color is the filtrate?
Is the filtrate clear or cloudy?
• Are any particles settling out?
• What, if anything, is left behind on the filter paper (Remember! Discoloration of the
filter paper does not mean that a solid was trapped)?
• Perform the Tyndall effect test by shining the laser beam through the filtrate in the
beaker. Can you see the light beam in the liquid (if yes, then positive for Tyndall
effect; if no, then negative for Tyndall effect).
5. Copy your observations into the class data table on the board. Record your classmates’
observations for the remaining filtrates.
6. Clean up (your filtrate can be washed in the sink and the filter paper thrown away), put
all equipment away, and wash your hands.
•
•
Analysis:
Classify each mixture as a suspension, co//old or solution. Use your mixture map as a guide.
Then complete the handout by copying your observations and classifications into the
appropriate data tables and answering the questions.