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6. Conservation of Mass Notes
6. Conservation of Mass Notes
6. Conservation of Mass Notes
How do the masses of the airplanes compare?
This comparison can help you understand the law of conservation of mass.
6. Conservation of Mass Notes
LAW OF CONSERVATION OF MASS
This law states that during a chemical reaction, matter is not created or destroyed.
The example below demonstrates this law.Number of hydrogen atomsBefore _____After _____Number of oxygen atomsBefore _____After _____
6. Conservation of Mass Notes
In a chemical reaction, all of the atoms present at the start of the reaction, are still there at the end of the reaction Atoms are NOT created or destroyed, they are only rearranged to form new substances.
6. Conservation of Mass Notes
The reactants are the atoms/molecules that are present before the reaction.
The products are the atoms/molecules that are present after the reaction.
All of the atoms in the reactants are present in the products. The amount does not change, they are only rearranged.
According to this law of conservation, the total mass stays the same before and after the reaction.
6. Conservation of Mass Notes
Depending on the situation, it may be hard to prove that matter is conserved in a reaction...
For example, when you strike a match, oxygen comes into the reaction from the air, but how much? Likewise, the products escape into the air. Again, how much?
6. Conservation of Mass Notes
Open Systems
An open system contains different types of matter that are interacting with each other. In open systems, matter can enter from or escape to the surroundings.
A majority of things on Earth are open systems: ecosystems, atmosphere, hydrosphere, solar system, and human body just to name a few.
If we want to be able to measure all the matter before and after a reaction, we have to be able to contain it.
6. Conservation of Mass Notes
Closed Systems
Closed systems are contained, where matter cannot enter or leave. A chemical reaction that occurs inside of a sealed, airtight container, is a closed system.
Conservation of matter in closed systems is MUCH easier to measure...
6. Conservation of Mass Notes
6. Conservation of Mass Notes
6. Conservation of Mass Notes
6. Conservation of Mass Notes
6. Conservation of Mass Notes
Are the following labs open or closed systems, and how do you know?Materials‑ vinegar, baking soda, graduated cylinder, bowl (for catching excess liquid), spoon 1. Pour 20 mL of vinegar into the graduated cylinder. 2. Place the graduated cylinder into the bowl. 3. Put one spoonful of baking soda into the graduated cylinder.
Materials‑ baking soda, calcium chloride, water, plastic bag, spoon, small beaker 1. Pour 10 mL of water into the beaker. 2. Put one spoonful of the baking soda in one corner of the plastic bag. 3. Put one spoonful of calcium chloride in the other corner of the plastic bag. 4. Set the beaker in the bag. DO NOT MIX THE CORNERS TOGETHER YET. 5. Seal the bag then mix the substances together.
6. Conservation of Mass Notes
Think of our baking soda & vinegar lab station.
Materials‑ vinegar, baking soda, graduated cylinder, bowl (for catching excess liquid), spoon 1. Pour 20 mL of vinegar into the graduated cylinder. 2. Place the graduated cylinder into the bowl. 3. Put one spoonful of baking soda into the graduated cylinder.
How can we can make it a closed system? Design a similar experiment to test the Law of Conservation of Mass.
6. Conservation of Mass Notes
