Mixtures: Solutions, Colloids and Suspensions EQ: What is matter and how can its properties be described?

More Mixtures We know that a mixture does not have a definite chemical composition and can be classified as heterogeneous mixtures and homogeneous mixtures. Another way to classify mixtures is as a solution, a colloid or a suspension

Imagine… It’s a hot summer day… You have been outside and you are really thirsty A tall, cool glass of water from the tap would taste great. But what exactly is tap water?

Tap water is more than just water.. It’s a mixture of water (H2O) and a variety of other pure substances, such as chlorine, fluoride, and gases such as oxygen and carbon dioxide are dissolved in tap water. These dissolved substances give tap water its taste Tap water is a mixture called a solution.

Solutions Tap water is one example of a mixture. A solution has the same properties throughout. It contains particles that are too small to see. Homogeneous A solution is a well-mixed mixture that contains a solvent and at least one solute *Mixture: something made of two or more substances --- elements, compounds or both– that are together in the same place but are not chemically combined.

Solutions --- Two categories Solvents Solutes The part of the solution that makes up the largest amount It dissolves the other substances. The smallest part It is dissolved by the solvent

T-P-S QUESTION: In sugar water, what is the solvent and what is the solute? Answer: Water is the solvent and sugar is the solute

Solutions Water is called the “universal solvent” because it dissolves so many other substances. Water is the solvent in blood, sweat, tears, and the soil

T-P-S Question: Can a solution only be made with liquid solvents?

T-P-S Answer: No, solutions can be made with other solvents. Any combination of gases, liquids, and solids can make up solutions.

Colloids A colloid is a mixture containing small, undissolved particles that do not settle out. *Particle: a minute portion of matter It is a mixture of two different states of matter A colloid contains larger particles than a solution. Homogeneous The particles are still too small to be seen easily, but are large enough to scatter light EX: mayonnaise, shaving cream, whipped cream

T-P-S Question: Which of the following are examples of colloids? a. fog b. salt water c. milk d. Snow globe

T-P-S Answer: Fog milk

Suspensions A suspension is a mixture in which particles can be seen and easily separated by settling or filtration. EX: pepper and water, glitter nail polish, instant lemonade Unlike a solution, a suspension does not have the same properties throughout. It contains visible particles that are larger than the particles in solutions or colloids Heterogenous

T-P-S Question: How does a suspension differ from a solution? Answer: A solution has same properties throughout and a suspension does not. A suspension contains visible particles that will settle out - they are larger than the particles in a solution.

Particles in a Solution So why then, do solutes seem to disappear when you mix them with a solvent? If you had a microscope powerful enough to look at the mixtures particles, what would you see? When a solution forms, particles of the solute leave each other and become surrounded by particles of the solvent

Particles in a Solution An ion is a group of atoms with an electric charge. When an atom loses an electron, it becomes a positive ion. When an ionic solid mixes with water, the positive and negative ions are attracted to the polar water molecules.

T-P-S Question: What happens when an atom gains an electron? Answer: It gains a negative charge and becomes a negative ion.

Particles in a Solution A solution of ionic compounds in water conducts electricity such as in salt water. Solutions such as sugar water have no ions and will not have conductivity.

Effects of Solutes on Solvents Solutes lower the freezing point and raise the boiling point of a solvent. This is the reason that antifreeze mixed with water in a car’s engine help to keep a car’s engine from overheating or freezing up.

Solute LAB Problem: How is the temperature of water affected by salt being added to it? Hypothesis: When salt is added to water, then the temperature of the water _____________. Materials: glass beaker salt 50 milliliters of water teaspoon thermometer paper and pencil

Procedure: Place 150ml of water into a clear beaker. Take the temperature using thermometer and write on your chart. Add 1 teaspoon of salt and stir thoroughly. Wait five minutes and take temperature. Write on your chart Continue steps above until 4 teaspoons have been added.

Salt Water Temperature Salt Content Temperature No salt added _______________°Celsius 1 teaspoon 2 teaspoons 3 teaspoons 4 teaspoons

Solute Lab (cont’d) Write a one paragraph summary about the findings of your lab. Also write how this lab relates to adding rock salt to our bags when we made ice cream.