Study Guide for TEST on WEDNESDAY, FEB. 22

·         When a new material forms when two or more materials are mixed, a chemical reaction has occurred.

·         A solution is formed when two solids dissolve (disappear) and the mixture becomes a clear liquid.

·         If you use a balance to measure two liquids, you can infer the side of the balance with the liquid that is a solution will be lower and heavier.

·         Evidence of a chemical reaction can include bubbles & fizzing, which means a new material (a gas) was produced.

·         It is possible for different materials to have different solubilities. For example, many grams of citric acid will dissolve in 50 mL of water. Fewer grams of salt will dissolve in 50 mL of water.

·         Be able to explain which solution is more concentrated. Be able to justify your answer with a comparison ratio of the amount of solute to the amount of water.

·         To separate a mixture, add water to the mixture. Stir to dissolve any particles if possible. Use a screen to separate the larger particles (gravel). Use a paper filter to separate the finer particles (powder). Evaporate the water to separate the finest particles (salt).

·         After a chemical reaction has occurred, a white solid settles to the bottom and leaves a clear liquid. The precipitate is proof of a chemical reaction.

·         Saturated solutions have the same concentration.

·         Once a solution is saturated, no more solute can dissolve in the solution. It cannot become more concentrated.

·         To prove that two solutions contain the same amount of solute, evaporate the solutions and compare the shape of the crystals. The same shape indicates the likelihood that the solute is the same in both solutions.  

·         A chemical reaction can be indicated by bubbling and fizzing, which means a gas has formed. Gas is a new material. A new material indicates a reaction.

·         The following indicate a chemical reaction has occurred:

o   A new material is formed when 2 liquids are mixed

o   A solid forms when 2 liquids are mixed

o   A gas bubbles out when 2 liquids are mixed

·         An example of a chemical reaction would be rust on an outdoor toolshed.