Grade 7 Science Chapter 8 and 9.1 Some substances...

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

For each of the following situations identify the solute

and the solvent:

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.


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


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.


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.

Ability to Dissolve

Soluble: If something is ABLE to dissolve

Ex: Sugar cube in water

Ability to Dissolve

Insoluble: If something is UNABLE to dissolve

Ex: Plastic in water

Soluble or Insoluble?

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




Soda Water

Carbon Dioxide

Gas Water Liquid




Vinegar Acetic Acid

Water




Vinegar Acetic Acid

Liquid Water Liquid




Salt water

Salt Water




Salt water

Salt Solid Water Liquid


**Alloy: Solutions made from two or more metals.



Brass Zinc Copper


**Alloy: Solutions made from two or more metals.



Brass Zinc Solid Copper Solid

Homework

Complete Homework Questions!

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.

(b).The water’s temperature increased by 5 degree Celsius.

#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.

(b).The liquid took only a few minutes to boil.

#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.

(b).This solid is heavier than that one.

#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.

(b).He drinks 2L of water each day.

#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:


Unsaturated: Is when solute is able to dissolve at a certain temperature

Draw in the beakers below what happens when a solution is 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:

Question to ponder...Can a solution that is concentrated be

called unsaturated? Explain

Factors affecting solubility

Factors affecting the Rate of dissolving

Factors that affect the rate of dissolving include:

1. Surface area of the solute2. Temperature3. Pressure

Surface area of solute

The smaller the solute particles, the quicker they will dissolve

Temperature

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

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

Pressure

As pressure increases, the solubility of a gas increases.

Homework

Complete Homework Questions!

Lab

Lab activity!!

Section 9.1 - Last section!

Separating Solutions

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

Flotation

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

Evaporation

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.

Distillation

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!

Practice Questions

Unit Review Practice Questions

Chapter 8 & 9.1 Assignment

Due next class!

Grade 7 Science Chapter 8 and 9.1 Some substances...

Documents

Transcript of Grade 7 Science Chapter 8 and 9.1 Some substances...