The Law of Conservation of Matter. Weve talked about changes in matter The evaporation of a puddle...
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Transcript of The Law of Conservation of Matter. Weve talked about changes in matter The evaporation of a puddle...
![Page 1: The Law of Conservation of Matter. Weve talked about changes in matter The evaporation of a puddle of water Rust forming on a metal fence PHYSICAL CHEMICAL.](https://reader035.fdocuments.us/reader035/viewer/2022062413/5a4d1b937f8b9ab0599c23d7/html5/thumbnails/1.jpg)
The Law of The Law of Conservation of Conservation of
MatterMatter
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We’ve talked about changes in matter…
• The evaporation of a puddle of water
• Rust forming on a metal fence
PHYSICAL
CHEMICAL
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HOWEVER…• No matter is created or destroyed by
such changes!
• The total amount of matter remains constant.
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The Law of Conservation of Matter• During a chemical reaction, matter
cannot be created or destroyed.
• Even though the matter may change from one form to another, the same number of atoms exists before and
after the change takes place!
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Law of Conservation of MassLaw of Conservation of Mass
Total mass of reactants =
Total mass of productsAntoine Lavoisier
Mass is neither created nor destroyed during chemical or physical reactions.
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Since the overall mass of the matter does not
change…• The mass of the reactants – the
substances there before the reaction occurs – must equal the mass of the product – the substances there after the reaction takes place.
Mass of Reactants
Mass of Products
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An Example of the L.C.M.• Test tube
containing lead lead nitratenitrate is placed upright in a flask that contains potassium iodidepotassium iodide.
• What are these?– REACTANTS!
• They don’t mix!
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• A stopper is put in place to create a closed system – an environment where matter cannot enter or escape.
• The mass of the system is found.
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• After the mass is found, the system is turned upside down so the lead nitrate can mix with the potassium iodide.
• They create lead iodide and potassium nitrate.
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•Although the matter changed in form, the total mass of the system remains unchanged.
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The Formation of Rust
• Iron– Hard, gray-colored
metal
• Rust– Flaky, orange-red
solid
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When iron reacts with oxygen in the air, they form rust or
IRON OXIDE.•This is written as:Iron + Oxygen Iron Oxide
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Fe Fe
Fe Fe
REAC
TANT
S
Each made of TWO
oxygen atoms
O2
O2 O2
PRODUCT
Fe2O3 Fe2O3
TAKE A LOOK AT
THE NUMBERS
How many Iron molecules?
How many Oxygen
molecules?
What about the
PRODUCT?
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All Chemical Reactions follow the Law of
Conservation of Matter • With Iron Oxide, the MASS STAYS
THE SAME!– The total number of iron atoms and
oxygen atoms in the reactants is the same as that in the product.
– The atoms were just rearranged!• No new atoms were created and none were
destroyed!
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Determining the Mass of Reactants and
Products• REMEMBER: The mass of the
reactants is always equal to the mass of the products.
Mass of Reactants
Mass of Products
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Example: Tin Fluoride• Tin + hydrogen fluoride -> tin fluoride +
hydrogen
• What’s the total mass of the reactants?– 158.72 g
• So what should the mass of the products be?– 158.72 g
118.7 g
40.02 g
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• Tin + hydrogen fluoride -> tin fluoride + hydrogen
• If we know the mass of the tin fluoride, can we figure out how much hydrogen was produced?– Subtract the mass of one product from the total
mass.
Total Mass of Reactants: 158.72 g
156.71 g
2.01 g
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How did scientists come up with this law?• Just like we did with the
vinegar and baking soda in a bag!
• They measured the mass of the reactants (vinegar and baking soda) and then, after the reaction took place, they measured the mass of the products (reactants + carbon dioxide)
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ANY QUESTIONS?