Science 24 Lab – Monday Dec. 8th, 2003-12-07
1. Go over Safety in the lab. Explain that each experiment we do will have unique safety
practices that you must adhere to.
2. Distribute handout on focusing and care for the microscope. Go over it with them.
-Give them some time to look at and focus three different slides. They must draw a
diagram of what they see and label it for each slide.
Lab #1. Page 117: “Yeast Power”. **Start the yeast suspension 15 to 30 minutes
before class begins. Add 1 g of fresh yeast to 100 mL of warm water. Set aside until
the yeast is hydrated.
Make the glucose solution by dissolving 1g of glucose in 100 mL of warm distilled
water.
(Students wear safety goggles and an apron).
-Warn your students about being careful when working around the hot water bath.
-Benedict’s solution can cause acute irritation if it gets into the eyes. Make sure students
are wearing eye protection at all times whne handling this material.
-Have students clean up the work area and wash their hands thoroughly at the end of the
activity.
-Distribute BLM 7-1. Explain what they need to do.
Note: Use of Benedict’s Solution — It is very difficult to observe the chemical reactions
associated with cellular respiration. However, Benedict’s solution can be used as a
qualitative measure of the amount of sugar in a solution.
Benedict’s solution is used to measure the presence of sugar. Benedict’s solution
is blue. If it is added to a solution with a high concentration of sugar and then heated, the
precipitate will turn red-orange. If Benedict’s is added to a solution with a lower
concentration of sugar and then heated, the precipitate will turn a yellow-green colour. If
no sugar is present, the solution will stay blue.
If this investigation is performed carefully, students will be able to infer that
cellular respiration is taking place inside the yeast cells because the amount of glucose
will decrease. The one percent glucose/Benedict’s solution turns red-orange when heated.
If a solution of yeast is added to the glucose solution, these living organisms will use the
glucose for cellular respiration. As a result, the yeast-glucose-Benedict’s suspension,
when heated, will show a lower concentration of glucose; i.e., turn yellow-green or
remain blue if all the glucose has been consumed by the yeast.
Review photosynthesis: carbon dioxide + water + light energy  glucose + oxygen
Cellular respiration: glucose + oxygen  carbon dioxide + water + energy
Answers to BLM 7-1.
1. What was the purpose of test tube #1?
Ans. Test tube 1 is designed to demonstrate whether Benedict’s solution reacts with
anything in water or when heated. The solution stays blue, indicating that it doesn’t
react with water or when heated.
2. What is the purpose of test tube #2?
Ans. The purpose of test tube 2 is to show a positive Benedict’s test.
3. What happens to the colour of the Benedict’s if sugar is present in the dolution?
Ans. The precipitate formed will turn red-orange, indicating a relatively high
concentration of glucose.
4. In terms of cellular respiration, write an inference explaining your observations of
what happened in test tubes 3 and 4.
Answers may vary. Students should indicate that yeast uses glucose for cellular
respiration. The results of the Benedict’s solution test should indicate that there was a
lower concentration of glucose in the solution. From that, students should infer that the
yeast used glucose for cellular respiration.
Extend Your Skills
5. Look for the following word and chemical equations for cellular respiration:
glucose (solid) + oxygen (gas)  carbon dioxide (gas) + water vapour (gas)
C6H12O6(s) + 6O2(g)  6CO2(g) + 6H2O(g)
Have students check the equation to make sure that it is balanced.
Lab #2. Page 99: “Where Does Electricity Come From?”
Supplies: sandpaper
1.5 m thin
bare copper wire
toiler paper rolls
electrical tape
galvanometer (3rd upper cupboard)
bar magnet.
Discuss basic atomic model as a way to introduce the particles involved in the production
of electricity. In the model of the atom, there are two distinct parts:
-The nucleus is where protons and neutrons are found. Protons are positively charged;
neutrons are neutral particles that provide additional mass to the nucleus.
-A cloud of negatively charged electrons surrounds the nucleus. In metals, electrons can
move from atom to atom, producing an electric current.
-Ask students why they think copper is used so extensively for wiring. Guide the
discussion to raise the following points.
Copper:
 Is easily available, cheap, durable, and flexible;
 Has superior conductivity and tensile strength;
 Required less insulation;
 Resists stretching, nicks, break and corrosion;
 Installs easily; and
 Is an effective biocide.
A galvanometer is an instrument used to determine the presence, direction, and strength
of an electric current in a conductor. All galvanometers are based on the fact that a
magnetic needle is deflected by the presence of an electric current in a nearby conductor.
In general, the deflection of the needle is dependent on the strength of the current – the
stronger the current, the greater the movement of the needle.
Distribute handout
Pg. 100. Set up another galvanometer with more coils of wire around it. Have the
students complete the “What to do” questions on page 100. They need to answer “What
did you Find Out?” questions 1-3 on the back of BLM 6-1
1. What happens to the galvanometer needle when the number of turns of wire is
increased?
Ans. The galvanometer indicates a larger electric current.
2. Does it make any difference whether it is the magnet or the coil of wire that moves?
Ans. No
3. You have found how electric energy can be produced by moving a magnet through a
coil of wire. Explain how you can increase the amount of electric energy generated in a
system.
Ans. The amount of electricity generated can be increased by:
-increasing the speed that the magnet is passed through the coil of wire;
-increasing the amount of wire; or
-using stronger magnets.
Lab #3 – Pages 238 – 239 “Think Fast!” (Reaction Time)
Apparatus – metre stick.
Our fourth unit in Science 24 is called Motion, Change and Transportation Safety. In this
unit, you will be learning about statistics relating to traffic accidents and some of the
physics behind collisions.
A very important part of your ability to drive safely is your reaction time.
The time it takes you to recognize a problem and act on it is called reaction time.
The stopping distance when you drive a car is the distance the car travels between the
time when the driver sees a problem and then reacts to apply the brakes (reaction time),
and the vehicle’s braking distance (which is the distance the vehicle travels after the
brakes have been applied but before the vehicle stops).
Read through the investigation with the students.
For accuracy, the instructions need to be followed exactly as written. Make sure the
thumb and forefinger of the grabbing hand are spread 3 cm and that the metre stick is
positioned correctly. Collect data after each trial.
Encourage students dropping the ruler to be crafty about it. They can wait as long as they
want before dropping it. Turn it into a competition. Not only will they have more fun,
but the reslts will be more reflective of true reactions.
Distribute “Think Fast!” worksheet. BLM 13-5.
1. (a) Calculate the average distance the ruler travelled for each part of the
investigation. Record this in the last column of each table.
(b) Did your results improve from the first to the last trial for each part? If so, why?
Ans. The reaction times may improve as students get used to the process and begin to
anticipate the drop.
2. (a)
How did your scores for reaction time with distractions compare to your
base reaction time?
Ans. Students’ reaction times with distractions should be longer than their base
reaction times.(part 1)
(b) Did the complexity of the math affect your reaction time? Explain.
Ans. Students will likely find that harder math lengthens their reaction time
because they are more distracted by the math. The particular processes that
students find more difficult will vary.
(c) How does this relate to distractions on the road or in your car?
Ans. Having more distractions while driving is like doing the harder math
questions. Both lengthen reaction time.
3. Did dialling a phone affect your reaction time? If so, by how much?
Ans Dialling a cell phone should slow reaction times. Exact amounts will vary.
4. (a) Did dizziness affect your reaction time? If so, by how much?
Ans. Dizziness should slow/lengthen reaction times. Exact amounts will vary.
(b) What driver problem might this suggest?
Ans. The effect of dizziness simulates impairment (eg. from alcohol).
Conclude and Apply
5. What are some distractions that may slow your reaction time while driving? How can
you control or eliminate these distractions?
Ans. Look for answers such as:
weather
billboards and lights
people, animals, and scenery
conversations and music
ringing phone
performing another task such as applying make-up, eating or drinking, dialling,
adjusting controls, or looking at a map.
Many of these distractions can be eliminated simply by not doing them or by doing them
only when the vehicle is pulled off the road and stopped. Remind students that being
stopped at a stoplight still involves driving.
Extend Your Knowledge
7. Did your results confirm your hypothesis? Explain.
Ans. Answers will vary but students should find that their reaction time is slowing when
they are distracted, tired, dialing a phone, or dizzy. If they didn’t predict this, discuss
why their results might have been different from what they expected.
Lab #4: Page 265, “Try This”.
Set up hotwheel track ahead of time.
Distribute BLM 15-9.
Ensure students maintain a safe velocity, as collisions will undoubtedly occur. This
demonstrated the need for a safe following distance as well as a proper velocity.
*Read the “Did You Know?” box on page 265. This fact about stopping distance
illustrated how dramatically your stopping distance increases as your velocity increases.
When velocity doubles, the stopping distance may triple.
Lab #5: Page 279 “Collision Damage.
APPARATUS
• wooden ramp
• toy car
• metre stick
• heavy barrier
• light cardboard barrier
MATERIALS
• modelling clay
• chalk
Recommended
BLM 15–9, Collision Damage
Time Required
• 40–45 min
Safety Precautions
• Make sure no one is walking in the path of the cart during the trials, since this could
lead to injury.
Hints and Helps
• A stack of textbooks works well as a heavy barrier.
• The toy car should be big enough to contain the clay passenger. A dynamics cart would
work better and run farther than most toy cars.
• The softer the clay, the more it will show damage done to the passenger.
• The barrier should not be higher than the car. This will let the passenger fly free.
• Make sure the clay figurine is resting lightly on the car, not stuck to it.
Teaching Strategies
Have the students take care in measuring the distance the passenger flies, describing the
damage, and re-forming the passenger between trials. Students may get lost in the crash
portion of the procedure and forget to take care in these important steps.
Prompt students with the idea of the relationship between the velocity of the car
and the distance the passenger is thrown. Is the relationship linear or irregular?
Discuss whether or not it is a good idea to repeat the trials to see if the passenger
behaves the same way in identical trials. What might the results suggest about crashes in
real life?
Implementing the Investigation
• Limit groups to two or three students.
• Hand out copies of BLM 15–9, Collision Damage to help students conduct this activity
and record their observations.
Lab #5 – Page 200 “Blood Transfusions”.
Mixing blood from two individuals can lead to blood clumping or agglutination. Dr.
Landsteiner discovered that blood clumping is an immune system response that occurs
when the recipient of a blood transfusion has antibodies against a donor’s blood. The
agglutinated red blood cells clog blood vessels and stop blood circulation. The cells can
crack and the contents, such as hemoglobin, leak out. Hemoglobin becomes toxic when
outside the blood cells. As a result, agglutinated blood can result in death.
Blood Transfusions — During a transfusion, there has to be a correct match between a
donor and a recipient’s blood. A transfusion will work if the recipient has a blood group
that does not have antibodies against the donor blood’s antigens. But if the recipient has
antibodies that match the donor blood’s antigens, the red blood cells in the donated blood
will clump. Figure 11.3 shows which blood types can be safely mixed.
How Blood Is Typed — Blood is typed by mixing a sample of blood with reagents that
contain either A or B antibodies and observing what happens. Clumping means that the
blood has reacted with a certain antibody. If you know the antigens that reacted with a
specific antibody, it is easy to identify the blood type. For example, if clumping occurred
when a blood sample was introduced to a reagent with A antibodies, then you know that
the blood sample must contain A antigens that are reacting to the A antibodies in the
reagent. Therefore, the blood sample must be Type A.
• Type A blood clumps when it is introduced to A antibodies.
• Type B blood clumps when it is introduced to B antibodies.
• Type O blood does not react when it is introduced to either A or B antibodies.
• Type AB blood clumps when it is introduced to either A or B antibodies.
Note: The antigen on the surface of the red blood cell is the more critical element in
terms of blood compability; although the presence of antibodies compel medical
practitioners to match blood precisely. Point out to students that a person with blood type
AB has both antigens and can thus receive any one of the four types of blood (i.e., is a
universal recipient.) Figure 11.3b explains why people with certain blood types can
donate blood to those with other blood types.
Figure 11.3
Blood Type
Can Receive From
Can Donate To
A
A and O
A and AB
B
B and O
B and AB
AB — universal recipient
A, B, AB, and O
AB
O — universal donor
O
A, B, AB, and O
Figure 11.3b
Donor
O — no antigens (neither A nor B)
Recipient
O, A, B, AB (Because there are no antigens in blood type O, this type is
a universal donor.)
A — antigen A present
A, AB (Antigen A would be foreign to blood type B.)
B — antigen B present
B, AB (Antigen B would be foreign to blood type A.)
AB — antigens A and B both present
AB (Both antigens are present, so at least one will be foreign for blood
types A, B, or O.)
Advance Preparation
WHEN TO
BEGIN
1–2 months
before
1 day before
Day of
APPARATUS
• blood plates
WHAT TO DO
• Purchase simulated blood types A, B, AB, and O and simulated A and B antibodies from the school’s
science supplier.
• Organize materials and supplies.
• Photocopy BLM 11–6, Blood Transfusions.
• Set up the materials and apparatus in an easily accessible area.
MATERIALS
• simulated Type A blood
• simulated Type B blood
• simulated Type AB blood
• simulated Type O blood
• toothpicks
• simulated A antibodies
• simulated B antibodies
Recommended
• BLM 11–6, Blood Transfusions
Time Required
• 60 min
Safety Precautions
• Do not use actual blood.
• Have students clean up the work area and wash their hands thoroughly at the end of the
investigation.
Hints and Helps
• Approach the Canadian Red Cross Society for information about blood transfusions to
use in a classroom display.
• Obtain or make a visual that shows the antigens and antibodies present in each blood
type.
• Test the set-up the day before to be sure you get the desired results.
• Have students work in larger groups if apparatus and materials are limited.
Tell students that the differences in human blood are due to the presence or absence of
antigens and antibodies.
• The antigens are located on the surface of the red blood cells.
• The antibodies are in the blood plasma.
Individuals have different types and combinations of antigens and antibodies. Use
a visual that shows the antigens and antibodies present in each blood type to help explain
the concepts. See BLM 11–7, Blood Types.
Ask students if they know what blood group they belong to. Tell them that they
inherited their blood group from their parents.
Explain that it is important to match blood types during a blood transfusion and
what happens when blood clumps. Briefly explain why blood clumping happens. Tell
students that if they required a blood transfusion, blood type testing would easily
determine what type of blood they have.
Provide students with BLM 11–6, Blood Transfusions to help them complete the
investigation.
Review the procedure. Demonstrate the technique for mixing blood types and
antibodies.
• Ask students to refer to the poster or visual and use terms such as “antibodies” and
“antigens” to explain what causes clumping to occur. (If the blood sample clumps, it
means it has reacted with a specific antibody. This means the blood type in the sample
is not compatible with the blood type containing that kind of antibody. If the blood
sample does not clump, it means the blood type in the sample does not have the
antigens that bind to that antibody and the blood type in the sample is compatible with
the blood type containing that kind of antibody.)
• Ask why Type AB is called the universal recipient (Answer: the recipient has both A
and B antigens; blood will not form clumps).
• Review why Type O is called the universal donor (Answer: the donor has neither A nor
B antigens; blood will not form clumps).
Analyze Answers
1. (a) No reaction.
(b) Blood cells clumped together.
(c) No reaction.
(d) Blood cells clumped together.
(e) No reaction.
(f) Blood cells clumped together.
Conclude and Apply Answers
2. Look for the following ideas.
• Mixing some blood types can cause blood cells to clump together.
• Clumped blood cells clog blood vessels and stop blood circulation.
• This could result in a patient’s death.
3. Type O blood can be given to anyone; it has no antigens and it has both A and B
antibodies.