Chapter 8: Substances, Mixtures, and Solubility Vocabulary 1.Substance – matter that has the same...

Chapter 8: Substances, Mixtures, and Solubility

Vocabulary

1. Substance – matter that has the same fixed composition and properties.

2. Heterogeneous mixture- type of mixture where substances are not mixed evenly

3. Homogeneous mixture- Contains two or more substances that are evenly mixed on a molecular level but still are not bonded together

4. Solution- a homogeneous mixture that contains two or more substances that are evenly mixed on a molecular level but still are not bonded together

5. Solute- substance that dissolves 6. Solvent- the substance that dissolves the solute

7. Precipitate- solid that comes back out of its solution as a result of a chemical change

8. Aqueous-a solution in which water is the solvent


Substances (pg. 218)

Atoms and Elements

Substance is

• matter that has the same fixed composition and properties

• Cannot be broken down into simpler parts by ordinary physical processes

• Only a chemical process can change a substance into one or more new substances.


PHYSICAL PROCESSES CHEMICAL PROCESSES

Boiling Burning

Changing pressure Reacting with other chemicals

Cooling Reacting with light

Sorting


Atoms and Elements (Pg 218

• An element is an example of a pure substance; it cannot be broken down into simpler substances

• The number of protons in an element are fixed; cannot be changed unless the element changes

• Ex: all atoms with eight protons are oxygen atoms

Compounds

• Water is an example of a substance

• Always water, even when boiled or frozen

• It is a compound (made of two or more elements chemically combined)

• Compounds also have fixed compositions

• Ratio of atoms in a compound is always the same


Mixtures (Pg 219)

• Mixtures are combinations of substances that are not bonded together and can be separated by physical processes

• Ex: salt water, iron filings and sand, pulpy lemonade

• Mixtures do not always contain the same proportions of the substances they are composed of.

• Ex: lemonade (see example in text book)

• Heterogeneous Mixtures

• Heterogeneous mixture- type of mixture where substances are not mixed evenly

• Ex: watermelon (fruit and seeds), cold cereal and milk


Homogeneous Mixtures (pg. 220)

• Contains two or more substances that are evenly mixed on a molecular level but still are not bonded together

• Solution- another name for a homogeneous mixture

• Ex: ice pops-molecules of sugar and water are evenly mixed; you cannot see the sugar.


How Solutions Form (pg. 220)

• Solute- substance that dissolves

• Solvent- the substance that dissolves the solute

• The substance that is present in the greatest quantity is the solvent

Forming Solids from Solutions

• Crystallization- when a solute comes back out of its solution to form a solid (when solution is cooled or when some of the solvent evaporates

• Crystallization is a physical change

• Precipitate- solid that comes back out of its solution as a result of a chemical change

• Ex: soap scum in shower


Types of Solutions (pg. 221)

Solvent/State Solute/State State of Solution

Earth’s atmosphere

Nitrogen/gas Oxygen/gas/carbon dioxide/gas argon/gas

Gas

Ocean water Water/liquid Salt/solid oxygen/gas carbon dioxide/gas

Liquid

Carbonated beverage

Water/liquid Carbon dioxide/gas

Liquid

Brass Copper/solid Zinc/solid solid


Liquid Solutions (pg. 222)

• In liquid solutions, the solvent is a liquid

• The solute can be another liquid, a solid, or a gas

• The state of the solvent usually determines the state of the solution

Liquid-gas solutions

• Carbonated beverages are liquid-gas solutions

• Carbon dioxide gives the beverage its fizz and some of its tartness

• The beverage may contain other solutes such as the compounds that give it its flavor and color


Liquid-liquid Solutions (pg. 222)

• In liquid-liquid solutions, the solvent and solute are liquids

• Ex: vinegar (95% water-solvent, 5% acetic acid-solute)

Gaseous Solutions (pg. 222-223)

• Small amount of one gas is dissolved in a larger amount of another gas; gas-gas solution

• Ex: air we breathe is a gas-gas solution

• Nitrogen is the solvent (78%) and the other gases are the solutes


Solid Solutions (pg. 223)

In solid solutions, the solvent is a solid.

The solute can be a solid, liquid or gas

The most common solid solutions are solid-solid.

A solid-solid solution made from two metals is an alloy

It is possible to include elements that are not metals in alloys. ex: steel is an alloy that has carbon dissolved in iron


The Universal Solvent –Water (pg. 224)

An aqueous solution is one in which water is the solvent.

Water is known as the universal solvent because it can dissolve so many solutes.


(pg. 224-225)

Molecular Compounds

Compounds that contain covalent bonds

ex: a water molecule (polar)

Ionic Bonds

Bonds between ions that are formed by the transfer of electrons.

ex: NaCl (salt) is an ionic compound


(pg. 225)

How Water Dissolves Ionic Compounds

Properties of water: polar molecules attract negative and positive ions

ex: water dissolves table salt because its partial charges are attracted to the charged ions in the salt.

(see Figure 8 on pg. 225)


(pg. 226)

How Water Dissolves Molecular Compounds

Water dissolves molecular compounds like sugar by moving between the different molecules of sugar, separating them.

Sugar molecules that are dissolved in water spread out until they are spaced evenly in the water.

Sugar and water are both polar.


(pg. 226)

What Will Dissolve?

Like Dissolves Like

“like dissolves like” means that polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes

sugar + water are both polar

oil and water do not mix; oil molecules are nonpolar and water molecules are polar


(pg. 227)

How Much Will Dissolve?

Solubility- a measurement that describes how much solute dissolves in a given amount of solvent.

Solubility of a material has been described as the amount of the material that can dissolve 100 g of solvent at a given temperature;

Highly soluble: a large amount of solute can be dissolved in 100 g of solvent.

(see examples on pg. 227)


(pg. 227)


Solubility- a measurement that describes how much solute dissolves in a given amount of solvent.

Solubility of a material has been described as the amount of the material that can dissolve 100 g of solvent at a given temperature;

Highly soluble: a large amount of solute can be dissolved in 100 g of solvent.

Insoluble: extremely low solubility

ex: only .00025 g of barium sulfate will dissolve in 100 g of water at 25°C.

(see examples on pg. 227)


(pg. 227)


Liquid-Solid Solutions

temperature affects the solubility of many solutes (see graph on pg. 227)

Liquid-Gas Solutions

Increase in temperature decreases solubility of a gas in a liquid-gas solution


(pg. 228)


Saturated Solutions

saturated -solution that contains all of the solute it can hold under the given conditions.

EX: 204g of sugar in water is a saturated solution

A solution with less solute than it needs to become saturated is called an unsaturated solution.


(pg. 228)

Rate of Dissolving

A solute dissolves faster when:

• The solution is shaken or stirred

• The temperature is increased

• Increase in the area of contact between the solute and solvent (break up the solute into smaller pieces to increase surface area of solute that is exposed to solvent.)


(pg. 229)

Concentration-

How much solute is present compared to the amount of solvent.

• A concentrated solution has more solute per given amount of solvent than a dilute solution.

Measuring Concentration

See Applying Science (pg. 229)


(pg. 230)

Effects of Solute Particles

All solute particles affect the physical properties of the solvent such as boiling and freezing points.

ex: NaCL and water (see pg. 230)

Chapter 8: Substances, Mixtures, and Solubility Vocabulary 1.Substance – matter that has the same...

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