Chemical Reactions Introduction

What we know so far… We know about matter, atoms, elements, and compounds We know that the difference between a mixture and a solution We know that when we combine chemicals, that some sort of change happens within the substance. Now we will figure out what is really going on!

Mixtures and Solutions Mixture- any form of matter that contains a blend of more than one substance and can be separate by physical means. Ex.- the salt, pepper, iron, and sand activity. Solution- A mixture formed when a substance mixes completely with another substance. Ex- lemonade

Elements and Compounds Element- a substance that cannot be broken down during a chemical reaction. It combines with other elements to form compounds. Compounds- a substance that can be broken down into simpler parts, only by a chemical change.

Favorite Example: Making salt water H2O + NaCl H2O + Na + Cl Water + sodium chloride water + sodium + chloride H2O + NaCl H2O + Na + Cl Two sides to a chemical reaction Reactants and Products

Stuff that is formed from the reaction Solute Solvent H2O + NaCl H2O + Na + Cl Reactants Products Stuff that is formed from the reaction Stuff that goes into reaction

Law of Conservation of Matter Matter is never created nor destroyed in a chemical reaction. Huh? The same amount of stuff you start with, you end with in a chemical reaction, just in different forms.

Separate into individual elements on each side H2O + NaCl H2O + Na + Cl Separate into individual elements on each side H2O + NaCl H2O + Na + Cl 2 H 1 O 1 Na 1 Cl 2 H 1 O 1 Na 1 Cl

Temperature and Reactions Certain chemical reactions affect the temperature Remember when we mixed the glue, borax, and water? What happened? It got warm!

Endothermic Reactions Feel cold!  They pull heat out of their surroundings  Examples Cold Pack -Ammonium Nitrate reacts with water Ice melting

Exothermic Reactions Feel hot! Put heat in surroundings Heat Exits in an Exothermic reaction Examples Fire burning Hot pack Heating Magnesium strips

Formation of a gas When chemicals mix, sometimes gases are formed. Mixing baking soda and vinegar releasing carbon dioxide

Precipitate: is formed whenever a solid substance is formed

Rotten Milk is also a great Precipitate… You really didn’t think I would actually hunt for a picture of this stuff did ya?

But, this is what will happen if you don’t drink it and get calcium!

Color Change