Grade 7 Science

Grade 7 ScienceSolutionsSolutions a reviewA homogeneous mixture They appear as ONE substanceExamples: tap water, vinegar, gold jewelry

We will learn:identify the solute and the solvent in a variety of solutionsdistinguish between soluble and insoluble substancesdescribe the concentration and solubility of substances qualitatively and quantitatively

Solutions have 2 parts:SoluteThe substance that dissolves (found in less amounts)SolventThe substance in which the solute dissolves (found in the greatest amounts)

Solute= Salt in this case

Solvent= WaterPage 255: Solute or Solvent?A. Brass is used to make many objects. Brass is a solution of zinc metal in a copper metal.

B. Hydrogen peroxide is used to disinfect cuts. Hydrogen peroxide is a solution of 3% hydrogen and 97% water.

Solute or Solvent?C. Dental amalgam is a metal that is used to fill cavities. It is a solution of mercury in tin.

D. Deicing fluid is a cleaner used to clean car and truck windshields. It is made up of a solution of propylene glycol in water.

Solutions song!- Journey with Me! http://www.youtube.com/watch?v=3G472AA3SEs

Dissolving...To mix completely (the solute dissolves into the solvent.)Some substances are able to dissolve better than others.

For those about to dissolve- we solute you!

http://www.youtube.com/watch?v=VTmfQUNLlMYThe Particle Theory of Matter states that there are attractive forces between the particles.How are substances soluble?

In order to dissolve, the particles must be more strongly attracted to the particles of the solvent than to themselves. This means that the solute is soluble in that solvent.

If something is ABLE to dissolve then it is soluble.

For example, sugar dissolves in water.

Particle Theory- Dissolving animation

If the particles of the solute are more attracted to their own particles than the solvent particles, dissolving does NOT occur. The solute is said to be insoluble in that solvent. (ie. Mechanical)How are substances insoluble?

If something is UNABLE to dissolve then it is insoluble.

For example, sand does not dissolve in water.

Soluble or Insoluble?

solubleinsolubleSolvent or Not?Some materials are good solvents for some solutes but not others. For example, oil is insoluble in water but soluble in gasoline.

States of Solutes and Solvents- Put book and workbook away. Hand out exit cards. Below is an example!AirSolute: oxygen, carbon dioxide, other gases

Solvent: nitrogen (most of our air is actually Nitrogen!!)GasGasSoda:(a combination of carbon dioxide in water). Identify water or carbon dioxide as the solute/solvent and say which state they are.Solute: ?Solvent: ?State of Solute: ?State of Solvent: ?

Vinegar:(a combination of 3% acetic acid and 97% water). Identify water or acetic acid as the solute/solvent and say which state they are.Solute: ?Solvent: ?State of Solute: ?State of Solvent: ?

Filtered Sea Water: (salt in water). Identify water or salt as the solute/solvent and say which state they are.

Solute: ?Solvent: ?State of Solute: ?State of Solvent: ?

Brass (an alloy of a zinc metal in a copper metal) Identify zinc or copper as the solute/solvent and say which state they are.Solute:?Solvent: ?State of Solute: ?State of Solvent: ?

Grade 7 Science

Concentrations of Solutions

Concentration (p 4 of workbook; 264)The two cups below each had hot water with a teabag sitting in them. The time below the cupindicates how long the tea bag has been in the cup.

10 minutes 2 minutes

Concentration isThe quantity of solute that is dissolved in a certain quantity of the solvent.Can be described qualitatively or quantitatively.

Qualitative:

Using words such as like dilute or concentrated

Quantitative:

Using numbers. This is especially important when safety is an issue!

Student Activity1. Demo of qualitative concentration2. Demo of quantitative concentration

Student Practice Quantitative?#1(a).Food coloring made the water blue.

(b).Adding 3 mL of food coloring turned 250 mL of water blue.QualitativeQuantitative#2(a).The water became warmer.

(b).The waters temperature increased by 5 degree Celsius.QualitativeQuantitative#3(a).We needed just over a dozen floor tiles for our model room.

(b).We needed 14 floor tiles for our model room.QualitativeQuantitative#4(a).The liquid boiled in 5 min.

(b).The liquid took only a few minutes to boil.QuantitativeQualitative#5(a).The mass of this solid is 5g more than that one.

(b).This solid is heavier than that one.QuantitativeQualitative#6(a).He drinks eight glasses of water each day.

(b).He drinks 2L of water each day.QualitativeQuantitativeDilute vs. ConcentratedDiluteThere is a small mass of dissolved solute for a certain quantity of solvent.ConcentratedThere is a large mass of dissolved solute for a certain quantity of solventDilute vs. Concentrated- Explained Qualitatively

Dilute vs. Concentrated- Explained Quantitatively

Saturated vs. UnsaturatedSaturatedWill form when no more solute will dissolve at a certain temperatureUnsaturatedMore solute is able to dissolve at a certain temperature

Question to ponderCan a solution be considered to be concentrated be unsaturated? ExplainQuestion to ponderIf there are two glasses on Kool Aid on the table, one is unsaturated the other is saturated. How would you be able to tell the difference between the two?Question to ponder2. It is possible to unsaturate a saturated solution. Suggest ways you might be able to do this. (Hint: How could you make more sugar dissolve in a glass of water?)Grade 7 ScienceSolutions and SolubilityHow Does Temperature Affect Solubility?Complete Core Activity 8-2A page 268-9Rate of DissolvingFactors that affect the rate of dissolving include:Size of the soluteTemperaturePressure

Size of SoluteThe smaller the solute particles, the quicker they will dissolve

fasterTemperatureThe higher the temperature, the more solute and the faster the solute will dissolve

fasterPressureGases are more soluble in liquids under higher pressure (see page 267)

Opened bottle decreases pressure and bubbles come out of solutionQuantitative DescriptionExpressed as the amount of solute per unit volume.Examples:g/Lg/mLppm (parts per million)%

Converting g/mL to g/L**Remember there are 1000mL in 1 L.1g/mL = ? g/L1 x 1000 = 1000therefore 1000g/L

Practice Problems0.3g/mL = ? g/L300g/L8.9g/mL = ? g/L8900g/L