1. Law of Conservation of Mass

2. Let’s examine this chair. It has a mass of 39 kg and a weight of 86 lbs. (So, pretty heavy) The question is… Where does this mass come from?
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3. It is made up of many parts: Wood 29kg Nails 1kg Stuffing 1kg Cushion 3kg Cloth 5kg ___________________ 39kg
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4. Which part gives the chair its mass. They all do
Which part gives the chair its mass? They all do! The mass of the chair is exactly equal to the mass of the things that make up the chair. In fact, the mass of any piece of matter is equal to the combined mass of all the things it contains.
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5. Putting it together
The total mass of all objects is equal to the sum of the mass of its parts. The same is true for the objects weight, the weight of an object is equal to the weight of all its parts together.

6. That simply means that if we add up all the individual parts of the chair (wood, nails, cloth, stuffing, cushion) we can find the total mass of the chair. Wood + Nails + Cloth + Stuffing + Cushion = Total of Chair 29kg + 1kg + 1kg + 3kg + 5kg = 39kg
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7. Other examples
The weight and mass of a whole apple is equal to the sum of each cut up piece added together.
This Photo by Unknown Author is licensed under CC BY-NC-ND
This Photo by Unknown Author is licensed under CC BY-NC-ND

8. + =
450g
15g
465g
If you measure the mass of a glass of milk and the mass of some chocolate powder. Then you mix them together to make chocolate milk. The mass of the chocolate milk will equal to the mass of the milk and chocolate powder added together.

9. The frozen bottle of water and the liquid bottle of water will have equal mass and weight. **Only their density will change.