Matter and atoms

Matter and atoms

Conservation of Mass

• ​Mass is neither created nor destroyed during ordinary reactions or physical changes

• ​Whatever mass we start with we will end with

Open Ended

You react two compounds totaling a mass of 8 g. after the reaction the mass of the product is 7.3 g. How can this be true if mass has to be conserved?

​Law of definite proportions

• ​Any amount of a chemical compound contains the same proportions of atoms of each element

Multiple Choice

How many more atoms are in a molecule of H20 in 12g vs 2 g?

• 20 hydrogen,

  10 oxygen

• 10 hydrogen,

  5 oxygen 

• no difference

​Law of Multiple proportions

• ​compounds are composed of the same two elements, the ratio of the masses of the second element combined with a certain mass of the first is always a ratio of small whole numbers

​Dalton's Postulates

1. ​Matter is compose of particles called atoms

2. ​Atoms of an element are identical; Differents elements are different

3. ​Atoms cannot be subdivided, created, or destroyed

4. ​Compound are atoms combined in simple whole number ratios

5. ​Chemical reaction combine, separate, or rearrange atoms

Fill in the Blank

Why is postulate 3 partially wrong?

​Atoms can be subdivided!

• ​Protons

  • ​positive

  • ​Reside in the nucleus

  • ​1.673x10^-27 kg

• ​Neutrons

  • ​neutral

  • ​in Nucleus

  • ​1.675x10^-27 kg

• ​Electrons

  • ​Negative

  • ​Electron cloud

  • ​9.109x10^-31 kg