Students will conclude at the end of this activity that the combined weight of the reactants in a chemical reaction is always equal to the combined weight of the products.
Activity A :Borax and Glue
For the class:
- 4% sodium borate solution (Prepare by mixing one cup borax powder to 2 liters
of water, shake well.)
- food coloring (optional)
For each team of 3-5 students:
- 8--oz.paper cup
- permanent felt tipped marker
- graduated cylinder
- quart--sized plastic locking bag
- bottle of white glue
- plastic spoon for stirring
Activity B:Vinegar and Cream
For each team of 3-5:
- 2 clear plastic cups
- plastic spoon for stirring
- 1/2 cup heavy whipping cream
- 5 ml of vinegar
Background for Teachers
Both suggested learning activities in this lesson will help students understand the relationship between the weight of reactants and the weight of the products involved in chemical reactions. Each activity can be completed in about 40 minutes of class time. If sufficient time and materials are available, conduct both activities in class, but if you must choose between the two, your students will be thrilled with the Borax and Glue activity. The Cream and Vinegar activity could be assigned as homework and the results reported to the class.
Intended Learning Outcomes
1-Use science process and thinking skills.
2-Manifest scientific attitudes and interests.
3-Understand science concepts and principles.
4-Communicate effectively using science language and reasoning.
6-Understand the nature of science.
Activity A: Borax and Glue
Cooperative teams of 3-5 students should complete the following steps:(See "Team
- Using a ruler and a permanent felt tipped marker, make a mark 1/2 inch from
the bottom on the inside of the paper cup. Fill the cup to the mark with white
glue. This will be about 25 ml.
- Using a graduated cylinder, measure out 25 ml of water and add it to the
glue in the cup. Add 1-5 drops of food coloring, if desired, and stir well.
- Using a graduated cylinder, measure out 15-20 ml of sodium borate solution:
pour it into the plastic locking bag and seal the bag. The glue solution and
sodium borate solution are the reactants.
- Find the combined weight of the reactants by placing the bag with the sodium
borate solution and the cup with the glue solution on the scale at the same
time. Record the combined weight.
- Pour the glue solution into the plastic bag with the sodium borate solution.
Seal the bag and knead the mixture for a few seconds. Make and record observations.
- Remove the solid mass from the bag. As you remove the solid mass from the
bag, hold the mass over the bag for a few seconds to allow any liquid to drip
back into the bag.
- Reseal the bag and set it aside. Work the mass with your hands until it
forms a "Silly Putty "-type solid. Experiment with this material
and record observations of its special properties. The solid material and
the liquid left in the bag are the products of this chemical reaction.
- Find the combined weight of the products by placing the bag with the remaining
liquid, the "Silly Putty "-type solid, and the cup on the scale.
(Make sure students understand that it is necessary to weigh the cup because
its weight was included when the glue was weighed.) Record the weight.
- Compare the combined weights of the reactants and the products. Record what
you have learned.
After the teams have completed the activity lead a discussion about what they
learned. The following questions may be helpful:
- What evidence shows this is a chemical reaction? (Formation of a solid-like
material that is a completely new substance with different properties from
the glue and borax solutions.)
- Was the weight of the reactants equal to the weight of the products? (The
answer should be yes, but the students may have differences in their data.
Have them compare their data and discuss why they may not agree. Some possibilities
may be: Some of the liquid might have come off on hands while the "Silly
Putty " was being worked; scales are inaccurate; mistakes might have
occurred in taking or recording data; some "Silly Putty " may
have stuck to their hands.)
- Challenge students to write an equation that demonstrates what they have
learned. weight of reactants +bag and cup = weight of products + bag and cup
- Have a contest to name the "Silly Putty."
Activity B: Vinegar and Cream
Cooperative teams of 3-5 students should complete the following steps: (See
- Fill a clear plastic cup about 1/2 full of cream. Observe the cream and
record its properties.
- Pour about 15 ml of vinegar into another cup. Observe the vinegar and record
its properties. The cream and the vinegar are the reactants in this activity.
- Find the combined weight of the reactants by placing the cup of cream and
the cup with vinegar on the scale. Record the combined weight.
- Pour the vinegar into the cream and stir once or twice. Observe the mixture.
Describe what you see, feel and smell. (Make sure students understand that
while it is safe to smell cream and vinegar, it is unsafe to smell or inhale
some chemicals. Caution them never to smell unknown chemicals.) Is there evidence
of new substances being formed? Explain. Record your observations. New substances
formed from a chemical reaction are called products.
- Find the combined weight of the products by placing both cups on the scale.
Record the weight. (Make sure students understand that it is necessary to
weigh the empty cup because its weight was included when the vinegar was weighed.)
- Compare the combined weight of the reactants to the combined weight of the
products. Record what you have learned.
After the students have completed the activity, lead a discussion. The following
questions may be helpful.
- Did a chemical reaction take place when the vinegar and cream were mixed?
- What evidence suggests that a chemical reaction has taken place? (Formation
of a solid after two liquids have been mixed.)
- Is it possible to get the cream and vinegar back after they have been mixed?
(No)Why? (They have chemically changed into a completely different substance.)
- Challenge students to write an equation to show the relationship between
the weight of the reactants and the products. Combined weight of reactants
+(cups)=Combined weight of products +(cups).
- Have students write a statement to explain the relationship between the
weight of the reactants and the products. The combined weight of the reactants
in a chemical reaction is always equal to the combined weight of the products.
This activity is preparing and consuming food in the classroom. Utah state
law requires that a person with a food handler 's permit be present when food
is prepared for student consumption. Sanitary conditions must exist, such as
a kitchen or cafeteria.
After students have experimented with making curds in cream by adding vinegar,
they will enjoy applying their knowledge in making cheese. Lemon Cheese is simple
to make and is a tasty spread for crackers.
To make 6-8 ounces of Lemon Cheese you will need:
- large spoon
- 2 quart canning jar
- 1 quart of whole milk
- hot plate
- juice from two lemons
Step 1 Acidifying and Coagulation
Heat the milk to 100 degrees F in the canning jar in the saucepan of water.
Add the juice for two lemons and stir well. Let the milk set for 15 minutes.
Step 2 Draining
Pour the curds into a cheesecloth-lined colander. Tie the four corners of the
cheesecloth into a knot and hang the bag to drain for 1 to 2 hours or until
the curds stop draining. The drained liquid is whey. Chilled, with mint leaves
added, whey makes a refreshing drink.
Step 3 Mixing, Salting, and Spicing
Take the cheese out of the cheesecloth. You may have to scrape some cheese from
the cloth. The cheese can be lightly salted and herbs may be added if desired.
Additional Experiments with Borax and Glue:
After mixing glue and borax allow your students to explore further by predicting
the effects of altering the amounts of glue, water and borax, and have them
design experiments to test their hypotheses.
Experiment with Laundry Starch and Glue:
- 125 ml of liquid laundry starch
- 65 ml of white glue
- 2.5 ml of salt
First, mix the laundry starch and salt. Then add glue and stir continually.
Once a lump of material forms (making it difficult to stir), squeeze remaining
liquid from the lump. Compare this “Slime ” to the “Silly
Putty.” Experiment with the proportions.
Use this rubric to assess your students ' performances:
Student 's Name ____________________________________
|Descriptions and data clear and accurate. All observations
|Descriptions and data mostly clear and accurate. All observations
||Descriptions and data somewhat clear and accurate. All obervations
|Descriptions and data unclear and inaccurate. All observations
|Used time well and focused attention on the activity.
||Used time fairly well. Stayed focused on the activity most
of the time.
|Did the activity but did not appear very interested. Focus
was lost on several occasions.
|Participation was minimal OR student seemed negative about
This lesson is part of the Fifth Grade Science Teacher Resource Book (TRB3) http://www.usoe.org/curr/science/core/5th/TRB5/. The TRB3 is designed to be your textbook in teaching science curriculum to your students. This book covers all the objectives of each standard and benchmark. If taught efficiently, a student should do well on the End-of-Level (CRT) tests. The TRB3 is designed for teachers who know very little about science, as well as for teachers who have a broad understanding of science.