Science Post Test Next Wednesday 2/29

Mixtures and Solutions Post Test Review

·         When a solid disappears in a mixture and the mixture is clear, this is evidence that the solid and water have made a solution.

·         When two solutions are saturated they have the same concentration.

·         1 mL=1g so if a spoon of solid has a mass of 2 g and there are 3 spoonfuls of solid in the mixture and 100 mL of water, the total mass would be 3X2=6g + 100mL (100g)=106g

·         You can separate the dissolved solid from water through evaporation. The water evaporates into the air and the solid left in the dish will form crystals.

·         If three spoonfuls of solid do not saturate a liquid then 2 spoonfuls of solid would dissolve in the liquid as well. There would be nothing on the bottom of the cup.

·         Solubility cannot be changed by stirring more.

·         On a balance, the cup that has the most mass is the most concentrated. This is because when equal volumes of two solutions made with the same materials are compared, the one that is more concentrated will have the greater mass (weigh more).

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

·         Be able to design an experiment to find out if temperature affects the number of grams of salt it takes to saturate 50mL of water.

1. set up 3 cups of 50mL of water: 1 hot, 1 cold, 1 room temperature

2. add spoons of salt to each cup and stir until no more salt will dissolve

3. filter the undissolved salt from each of the solutions

4. weigh the cups against each other or find the mass of the 3 solutions in grams

·         Crystals of different materials have different shapes. The crystal shape can help you identify the solid material used to make the solutuion.

·         A chemical reaction is evidenced by a gas being produced and/or a precipitate forming.

·         Rust forming on a bike or a candle burning are 2 examples of chemical reactions.

·         A saturated solution will have particles undissolved on the bottom of the cup and evenly dispersed particles throughout the solution.

·         Be able to identify the most concentrated solution. Concentration is a comparison of the amount of solute to the amount of water (solvent). Think about how much solute is dissolved in each 50 mL of water and compare the ratios.