Download Law of Conservation of Mass - Mr. Littman`s Science Class

Wednesday, October 15th, 2014
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Get your homework out.
Homework
◦ Identify the products and reactants for the chemical
equations on your HW
 Write P or R
◦ Define the vocabulary words during class
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Do Now
1. How are physical changes different from chemical
changes?
2. Describe what happens to the mass of matter
before and after a physical or chemical change?
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SWBAT read a chemical equation by
identifying the products and reactants.
SWBAT describe the law of conservation of
mass.
Essential Question
 What is the law of conservation of mass and
what does it tell scientists about the reactants
and products of a chemical equation?
1.
2.
3.
4.
5.
6.
Baking soda in balloon
Vinegar in flask
Place balloon on flask
Measure mass
Dump baking soda into flask
Measure mass
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Before
◦ What do you expect will happen?
◦ What will the mass be?
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After
◦ What are your observations?
◦ Why did this happen?
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The law of conservation of mass
◦ Mass cannot be created or destroyed
◦ Draw a picture
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Product
Reactant
Coefficient
Subscript
1.
2.
3.
4.
5.
Answer the 3 questions on the back of the
reading on a sheet of lined paper.
When you are finished answering the
questions identify the reactants, products,
and coefficients of the 5 chemical equations
You can work with the people at your table.
You have 20 minutes to complete this
activity.
When you finish complete the vocabulary
and start the HW
1.
What information does a chemical equation
provide?
Chemical reactions tell us what substances
are reacting (being used up) and what
substances are being produced (those being
made). Chemical reactions also tell us the
ratios of the chemicals reacting and being
produced and the numbers each atom in the
reaction.
2.
What are reactants and products? How can
reactants and products be identified?
Reactants are the chemicals that are being
used up. Products are chemicals that are
being made. The reactants are always on
the left side of the arrow. The products are
always on the right side of the arrow.
3.
What are coefficients? Why are coefficients
important?
Coefficients are the numbers in front of the
formulas. Coefficients are important
because they give us the number of
molecules that react in a reaction. With the
coefficients we know the amount of 1
substance will react with another substance
1) Zn + 2 HCl --> ZnCl2 + H2 (Zn – 2, Cl – 2, H – 2)
Reactants
Products
2) 2 KClO3 --> 2 KCl + 3 O2 (K – 2, Cl – 1, O – 6)
Reactants
Products
3) S8 + 24 F2 --> 8 SF6 (S – 8, F – 48)
Reactants
Products
4) 4 Fe + 3 O2 --> 2 Fe2O3 (Fe – 4, O – 6)
Reactants
Products
5) 2 C2H6 + 7 O2 --> 4 CO2 + 6 H2O (C–4, H–12, O-14)
Reactants
Products
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Reactant
◦ A substance that exists before a chemical reaction.
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Product
◦ A substance that forms as a result of a chemical
reaction.
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Lets go back to the demonstration
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NaHCO3 + HC2H3O2  NaC2H3O2 + H2O + CO2
Reactants
Products
Number of atoms:
Na
H
C
O
1
5
3
5
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What is the law of conservation of mass and
what does it tell scientists about the reactants
and products of a chemical equation?

Identify the reactants and products of the
following chemical equation. Identify the
number of atoms of each element on each
side of the chemical equation.
1. FeS + 2HCl  H2S + FeCl2
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Reactants:
Products:
# of atoms:
# of atoms:
2. What is the law of conservation of mass?
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Identify the reactants and products of the
following chemical equations.
1. FeS + 2HCl  H2S + FeCl2
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Reactants: FeS, HCl # of atoms: Fe-1, S-1, H-2, Cl-2
Products: H2S, FeCl2 # of atoms: Fe-1, S-1, H-2, Cl-2
2. What is the law of conservation of mass?
• Mass cannot be created or destroyed.
• Mass before a physical or chemical change will be
the same as after the change.