8 th grade science. 1. solutions are mixtures of 2 or more substances. one substance dissolves...

8th Grade Science

1. Solutions are mixtures of 2 or more substances. One substance dissolves completely into the other like salt and water.

2. Solutions have at least 2 parts:

•One part called SOLVENT – present in the largest amount.

• It dissolves other substances. Ex. of a solvent is water.

3. The other part is the SOLUTE(S) – (a) smaller amounts. (b) Get dissolved in solvent. Ex. of solutes are salt, sugar, gases, flavors, metals, etc.

4. Definitions:

• SolutionSolution - - homogeneous mixture

• SolventSolvent - present in greater amount & dissolves the solute

• SoluteSolute - substance being dissolved

5. The coffee is the solvent, the sugar is the solute,

and the sweetened coffee would be the solution.

6. “Water as a Solvent”

a. Water is known as the “universal solvent.”

b. Universal Solvent—a substance in which almost any

substance will dissolve.

7. Gases and solids can be solvents too:

Solute

Solvent Solution

Gas Gas Air

Gas Liquid Soda water

Liquid Liquid Antifreeze

Solid Liquid Dental filling (silver in mercury)

Solid Liquid Ocean water (NaCl and other compounds in water)

Solid Solid Brass (zinc in copper)

Concentratio

n and

Solubility

8. Homogeneous Solutions form when solutes go in

between the solvent molecules.

Diluted Solution – little solute dissolved in solvent.

Concentrated Solution – relatively more solute dissolved in solvent.

9. Measuring Concentration – by comparing the amount of solute to the amount of solvent or to the total amount of solution.

% by Volume% by Volumeusually liquid in liquid

EX: 10% juice = 10mL juice + 90mL water

% by Mass% by Massusually solid in liquid

EX: 20% NaCl = 20g NaCl + 80g water

10. Solubility – is a measure of how well a solute can dissolve in a

solvent at a given temperature.

Solubility can change by changing temperature, Pressure, and type of

Solvent.

11. Unsaturated solution – CAN hold

more solute.

12. Saturated Solution – CANNOT

hold more solute.

UNSATURATED SOLUTION

SATURATED SOLUTION

13. Supersaturated Solution – holds more solute than normal because water molecules have been heated and moved apart so more solute will fit in between the water molecules.

SUPERSATURATED SOLUTION

14. Solutes and Solvents

a. What is a solute?

a. What is a solvent?

a. What is a solution?

15. Summarize how sugar dissolves in water.

• In two or three well-written paragraphs, tell the story from start to finish of how a sugar cube dissolves in a cup of water.

• Start from when you put the sugar cube in the water and explain what happened up until you couldn’t see the sugar anymore.

• Underline the terms

• Include these terms in your paragraphs: – dissolve – solute– solvent– solution– homogeneous – Mixture– Attract or

attraction– particles