grade 7 science chapter 8 and 9.1 some substances...
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Grade 7 Science Unit 3
Some substances dissolve to form solutions faster and more easily than others.
Chapter 8 and 9.1
Review
Solution: A homogeneous mixture ie. they appear as ONE substance
Examples: tap water, vinegar, gold jewelry, etc.
Solutions have 2 parts:
SoluteThe substance that
dissolves (found in less
amounts)Ex: sugar
SolventThe substance in which the solute
dissolves (found in the greatest
amounts)Ex :water
Situation Solute Solvent
A.Brass is used to make many objects. Brass is a solution of 35% zinc metal in a 65% copper metal
B.Hydrogen peroxide is used to disinfect cuts. Hydrogen peroxide is a solution of 3% hydrogen and 97% water.
Situation Solute Solvent
A.Brass is used to make many objects. Brass is a solution of 35% zinc metal in a 65% copper metal
Zinc Copper
B.Hydrogen peroxide is used to disinfect cuts. Hydrogen peroxide is a solution of 3% hydrogen and 97% water.
Hydrogen Water
Situation Solute 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.
Situation Solute Solvent
C.Dental amalgam is a metal that is used to fill cavities. It is a solution of mercury in tin.
Mercury 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.
Propylene glycol Water
Mixing Solutions
Dissolving: To mix completely ie. the solute dissolves into the solvent.
Some substances are able to dissolve better than others.
How are substances soluble or insoluble?
The Particle Theory of Matter states that:
** “there are attractive forces between the particles”.**
How are substances soluble?
Soluble substances:The particles must be more attracted
to the solvent particles than to themselves.
How are substances insoluble?
Insoluble substances:If the particles of the solute are more
attracted to themselves than to the solvent particles
Solvent or Not?Some materials are good solvents for some solutes but not others.
For example:Oil- Oil is insoluble in water but - Oil is soluble in gasoline.
Can solutes and solvents be in differents states?
Yes! All states of matter:
Solids, Liquids and Gases
States of Solutes and Solvents
Solution Solute State of Solute
Solvent State of Solvent
Soda Water
Carbon Dioxide
Water
States of Solutes and Solvents
Solution Solute State of Solute
Solvent State of Solvent
Soda Water
Carbon Dioxide
Gas Water Liquid
States of Solutes and Solvents
Solution Solute State of Solute
Solvent State of Solvent
Vinegar Acetic Acid
Water
States of Solutes and Solvents
Solution Solute State of Solute
Solvent State of Solvent
Vinegar Acetic Acid
Liquid Water Liquid
States of Solutes and Solvents
Solution Solute State of Solute
Solvent State of Solvent
Salt water
Salt Water
States of Solutes and Solvents
Solution Solute State of Solute
Solvent State of Solvent
Salt water
Salt Solid Water Liquid
States of Solutes and Solvents
**Alloy: Solutions made from two or more metals.
Solution Solute State of Solute
Solvent State of Solvent
Brass Zinc Copper
States of Solutes and Solvents
**Alloy: Solutions made from two or more metals.
Solution Solute State of Solute
Solvent State of Solvent
Brass Zinc Solid Copper Solid
Concentrations of Solutions
Concentration: The quantity of solute that is dissolved in a certain quantity of the solvent.
Can be described qualitatively or quantitatively.
Concentration can be described two ways:
Qualitative*Quality
Using words Like “dilute” or “concentrated”
Quantitative*Quantity
Using numbers. This is especially important when
safety is an issue!
Student Practice... (page 471)
Qualitative or Quantitative? #1(a).Food coloring made the water blue.
(b).Adding 3 mL of food coloring turned 250 mL of water blue.
Student Practice... (page 471)
Qualitative or Quantitative? #1(a).Food coloring made the water blue.
Qualitative
(b).Adding 3 mL of food coloring turned 250 mL of water blue.
Quantitative
#2(a).The water became warmer.
Qualitative(b).The water’s temperature increased
by 5 degree Celsius.Quantitative
#3(a).We needed just over a dozen floor tiles for our model room.
(b).We needed 14 floor tiles for our model room.
#3(a).We needed just over a dozen floor tiles for our model room.
Qualitative(b).We needed 14 floor tiles for our
model room.Quantitative
#4(a).The liquid boiled in 5 min.
Quantitative(b).The liquid took only a few minutes
to boil.Qualitative
#5(a).The mass of this solid is 5g more than
that one.Quantitative
(b).This solid is heavier than that one.Qualitative
#6(a).He drinks eight glasses of water each
day.Qualitative
(b).He drinks 2L of water each day.Quantitative
Dilute vs. Concentrated
Dilute:A small amount of dissolved solute in
the solvent.Concentrated:There is a large amount of dissolved
solute in a solvent
Mini - Activity
The two cups below each had hot water with a tea bag sitting in them.
The time below the cup indicates how long the tea bag has been in the cup.
Directions:1.Supposing these were clear cups, use
a brown lead to color how dark you think the tea would be in each cup.
2.Write: dilute solution or concentrated solution under the cup you think it describes.
Think about it!
If we keep adding solute, eventually it will stop dissolving…
Think: if you keep adding salt, eventually there will be too much to dissolve
What do we call this?
Saturated vs. Unsaturated
Saturated: Is when no more solute will dissolve at a certain temperature
Draw in the beakers below what happens when a solution is saturated:
Saturated vs. Unsaturated
Saturated: Is when no more solute will dissolve at a certain temperature
Draw in the beakers below what happens when a solution is saturated:
Saturated vs. Unsaturated
Unsaturated: Is when solute is able to dissolve at a certain temperature
Draw in the beakers below what happens when a solution is unsaturated:
Saturated vs. Unsaturated
Unsaturated: Is when solute is able to dissolve at a certain temperature
Draw in the beakers below what happens when a solution is saturated:
Factors affecting the Rate of dissolving
Factors that affect the rate of dissolving include:
1. Surface area of the solute2. Temperature3. Pressure
Temperature and solubilityAs temperature increases, the solubility
of a solid increases
BUT
As temperature increases, the solubility of a gas decreases.
Pressure
Gases are more soluble in liquids under higher pressure
Opened bottle decreases pressure and “bubbles” come out of solution
Partner activityhow you would separate the following mixtures...
- Salt water - Muddy water - Nuts and bolts - Iron filings and sand - Vegetable oil and sand - Vegetable oil and water - Salt and pepper
DISCUSSION QUESTION
“Are the components you have separated still mixtures, or are they
pure? Why or why not?”
SEPARATION TECHNIQUES
1.Mechanical Sorting:
Used to separate the parts of a mixture, often based particle size.
Examples: floatation & magnetism
2. FILTRATION:
A common way to separate solid particles from a mixture
The filters can have holes of varying sizes...small to microscopic.
EVAPORATION:
Uses a change of state from a liquid to a gas.
**The solute and solvent have different boiling points
PAPER CHROMATOGRAPHY:
Used to separate the colored substances in a mixture such as ink.
Used to separate the solvents in a mixture.
DISTILLATION:
Uses two changes of state: - evaporation - condensation
It allows you to recover BOTH the solute and solvent from a solution.
SEPARATION TECHNIQUESIN THE HOME:
- Colanders
- Clothes dryers
- Window screens
- Coffee percolators
- Salad spinners
Any others?
Activity!
Demonstration and mini activities!
Magnetism, filtration, paper chromatography and Distillation!
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