Matter: Anything that has mass and takes up space, or volume.

Chemical Reactions H 2 + Cl 2  2 HCl

Use a chemical formula to determine which elements form a compound. Use the formula to find the elements present in the molecule and the number of atoms of each element. KEY WORDS Chemical formula Subscript

Type 1 - Elements combine with each other. Type 2 - Molecules react together. Type 3 - Compounds are broken down into atoms. All reactions result in a new substance with different properties than before. Chemical Reaction: A movement of electrons between combining atoms that results in the formation of a NEW substance.

The Law of Conservation of Matter: In any chemical reaction matter cannot be created or destroyed. Atoms will rearrange to form new compounds, but the number and type of atoms will not change during the reaction.

1000 kg

subscript Chemical formula - shows the type and amount of each atom present in a compound. H O H H H O +

and 3 atoms of oxygen H2OH2O3 form 3 molecules of water. 6 atoms (3 x 2) of hydrogen H H O H H O H H O

CompoundNumber of particles Total of each element KHCO 3 1K – 1 H – 1 C – 1 O – 3 AlCl 3 3Al – 3 Cl – 9 CBr 4 6C – 6 Br – 24 H 2 SO 4 5H – 10 S – 5 O – 20 C 11 H 22 O 12 4C – 44 H – 88 O –

All atoms present before a chemical reaction must be present after. (Law of Conservation of Matter) Chemical formula represents the type and amount of elements that make up the compound AlCl 3 – show 1 atom of aluminum and 3 atoms of chlorine combine to form 1 compound.