Chemistry

**Changes in Matter**

\-Chemical change: A change in the identity and properties of matter

\-Chemical property: A characteristic of a substance that is observable only when the substance interacts with another substance

\-Conductivity: The ability to transfer heat or electric current

\-Extensive property: A property dependent on the amount of sample present

\-Flammability: The tendency to ignite or burn in air

\-Intensive property: A property dependent only on a substance’s identity and not on the amount of sample present

\-Malleability: The ability to be reshaped by the application of physical force

\-Matter: A thing or substance that has mass and occupies space

\-Physical change: A change in one or more physical properties of a substance but not in the identity of the substance

\-Physical property: A characteristic of a substance that can be observed without changing the identity of the substance

\-Reactivity: The tendency of a substance to interact with other substances to form new substances

\-Transparency: The degree to which light can pass through a substance

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*Matter*

Matter is anything that has mass and takes up space.

Matter can be a solid, liquid, or gas.

Examples of matter in a kitchen:

\-Chef

\-Ingredients

\-Cooking utensils

\-Air

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*Properties of Matter: Physical Properties*

A physical property is a characteristic of a substance that can be observed without changing the identity of the substance.

\-Color, Odor, and Texture

\-Melting Point and Boiling Point

\-State of Matter

\-Mass, Weight, and Density

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*Properties of Matter: Chemical Properties*

A chemical property is a characteristic of a substance that is observable only when the substance interacts with another substance.

*Examples include:*

\-Flammability: Ability to burn in air

\-Reactivity: Ability to interact with other substances to produce new substances

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*Chemical and Physical Properties*

Must multiple substances be present?

\-Yes: Chemical property

\-No: Physical property

Does a new substance form?

\-Yes: Chemical property

\-No: Physical property

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Intensive Properties Include:

\-Boiling Point

\-Melting Point

\-Density

\-Conductivity

\-Magnetism

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Extensive Properties

\-Mass

\-Volume

\-Length

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*Characteristic Properties*

Characteristic properties of a substance can be used for identification.

\-Color: Yellowish

\-State at room temperature: Solid

\-Melting point: 1,064.43\`C

\-Boiling point: 3,080\`C

\-Density at room temperature: 19.32 g/cm3  

\-Luster: Metallic

\-Malleability/ductility: High

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*Physical Changes*

A physical change results in a change in some of the physical properties of matter but not its identity.

Examples include:

\-Melting

\-Boiling

\-Cutting

\-Bending

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*Chemical Changes*

A chemical change results in a change in the identity and properties of matter.

Examples include:

\-Burning

\-Cooking

\-Reacting with water

\-Reacting with air

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*Indicators of Chemical Change*

Possible indicators of chemical change include:

\-Color change

\-Solid disappearance

\-Gas formation

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Possible indicators of chemical change include:

Precipitate formation

\-Solid that forms from a liquid during a change process

Light and heat production

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*Chemical and Physical Changes*

Do any new substances form?

\-Yes: Chemical change

\-No: Physical change

Do chemical properties change?

\-Yes: Chemical change

\-No: Physical change

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**Lab: Physical and Chemical Changes**

In Order

\-Step

\-Material

\-Change(s) Observed

\-Type of Change(Physical/Chemical)

\-Explanation

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*Calcium Carbonate:*

\-Physical change because even though a particle size change was observed, the calcium carbonate retained its original properties and was not transformed into a new substance

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*Calcium Carbonate and Hydrochloric Acid*

\-Chemical change because gas formation was observed, which indicated that the calcium carbonate was transformed into a different substance

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*Water*

\-Physical change because even though gas formation was observed, the water was undergoing a state change, which means that its original properties are preserved

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*Copper(II) Sulfate Pentahydrate*

\-Chemical change because gas was released along with a color change, which indicated that the copper(II) sulfate pentahydrate was transformed into a different substance

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*Iron Filings and Sulfur*

\-Physical change because even though a color change occurred, each solid maintained its original properties, which could be seen as soon as the magnet was applied

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*Potassium Iodide and Lead Nitrate*

\-Chemical change because both a color change and a solid formation were observed, which provide strong evidence of a new substance

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*Magnesium and Hydrochloric Acid*

\-Chemical change because a temperature change occurred, a solid disappeared, and a gas was produced

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*Candle*

\-Both physical change because the wax melted and changed shape and chemical change because light and heat were formed as the candle burned

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**Elements, Compounds, and Mixtures**

\-Chromatography: A method of separating solutions in which the solute is separated by the density or size of particles

\-Compound: A pure substance made up of two or more elements that are chemically combines

\-Distillation: A process in which a mixture is separated using differences in boiling point between the different components of the mixture

\-Element: A pure substance made up of only one type of atom

\-Heterogeneous mixture: A mixture whose components can be distinguished

\-Homogeneous mixture: A mixture whose components cannot be distinguished and that appears as a single phase

\-Mixture: A combination of pure substance that are not chemically combined

\-Pure substance: A type of matter that cannot be broken down into simpler components without undergoing a chemical change

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*Classification of Matter*

Pure Substances

\-A pure substance is a type of matter that cannot be broken down into simpler components without undergoing a chemical change

Examples:

\-Water(H2O)

\-Salt(NaCI)

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*Examples of Elements*

An element is a pure substance consisting of only one type of atom.

Examples:

\-Sodium(Na)

\-Chlorine(CI

\-Iron(Fe)

\-Oxygen(O2)

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*Compounds*

A compound is a pure substance made up of two or more different kinds of atoms

\-Atoms cannot be separated through physical processes

\-Atoms are chemically bonded together in a fixed ratio)

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*Examples of Compounds*

\-Water(H2O)

\-Salt(NaCI)

\-Emerald(Be3, AI2(SiO3)6)

\-Rust(Fe2, O3)

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A mixture is a combination of two or more pure substances that are not chemically combined.

\-Can be separated by physical means: Distillation, filtration, or sorting

\-Don’t have fixed ratios between components

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A homogenous mixture appears as a single phase.

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A heterogeneous mixture appears to consist of two or more components that are distinguishable.

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*Separation of Mixtures*

\-Sorting

\-Filtration

\-Distillation: A process in which a mixture is separated using the differences in boiling points of the different components of the mixture

(Example: Separation of gasoline from other oil components)

\-Chromatography: A process in which a mixture is separated using differences in the ability of the components of the mixture to pass through a substrate

(Example: Separation of colors in pigments)

Separation methods take advantage of the physical properties of the materials

(-Solubility)

(-Boiling point)

(Particle size)

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**Mixtures and Solutions**

\-Alloy: A homogeneous mixture of metals

\-Brownian motion: The constant, random motion of particles

\-Centrifuge: A method of separating mixtures in which spinning is used to separate substances according to density

\-Chromatography: A method of separating solutions in which the solute is separated by density or size of particles

\-Colloid: A class of suspension with smaller particles that are dispersed in a manner that prevents them from being filtered easily or setting rapidly

\-Crystallization: A method of separating solutions that involves evaporating the solvent from a solution, causing the solute(s) to crystallize

\-Distillation: A process in which a mixture is separated using differences in boiling point between the different components of the mixture

\-Heterogeneous mixture: A mixture that contains more than one phase and in which the characteristics of the particles vary throughout the mixture

\-Homogeneous mixture: A mixture that appears as one phase and in which the particles have uniform characteristics throughout

\-Long standing: A method of separating mixtures that involves leaving the mixture to stand over time

\-Solute: A substance that gets dissolved by the solvent in a solution; a substance present in a relatively smaller amount in a solution

\-Solution:  A homogeneous mixture that is made up of two or more substances that appear as one phase

\-Solvent: The substance that dissolves the solute in a solution; the substance present in the larger relative amount in a solution

\-Suspension: A type of heterogeneous mixture containing particles large enough to settle out or capable of being filtered out

\-Tyndall effect: The scattering of light passing through a transparent medium

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*Homogeneous and Heterogeneous Mixtures*

Homogeneous mixture: Evenly distributed

Heterogeneous mixture: Uneven distribution

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*Solutions*

Each solution is made up of a solvent and one or more solutes

\-Solutes and solvents can be solids, liquids, or gasses

\-The solutes and solvent of a solution can be in any phase

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*Suspensions*

Suspension: A type of heterogeneous mixture containing particles large enough to settle out or capable of being filtered out

Examples:

\-Muddy river

\-Flour-and-water mixture

\-Blood

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*Colloids*

Colloid: A class of suspension with smaller particles that are dispersed in a manner that prevents them from being filtered easily or settling rapidly

Examples:

\-Homogenized milk(If it’s not homogenized a layer of cream will appear above the milk)

\-Fog(heterogeneous mixture)

\-Mayonnaise(Emulsion. An emulsion is two or more liquids that are normally not able to mix, like water and oil. But they’re held in suspension through the addition of another substance, called an emulsifying agent. In mayonnaise, the agent is egg yolk)

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*Differentiating Colloids from Suspensions and Solutions*

How can you tell colloids, suspensions, and solutions apart?

\-Brownian motion: Constant, random motion of particles

(Ex. Dust particles in a sunbeam moving randomly)

(Observed in colloids and solutions)

(Not observed in suspensions)

\-Quick settling

(Observed in suspensions; suspension must be frequently stirred particles suspended)

(Not observed in most colloids or solutions)

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*The Tyndall Effect*

Tyndall effect: The scattering of light passing through a transparent medium

\-Exhibited by colloids and some suspensions

\-Not exhibited by solutions

VOC: Volatile Organic Compounds.

Ex. Pollen suspended in the air.

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Ex.

Imagine two clear glasses of liquid. The first glass contains a solution, whereas the second glass contains a colloid. If you had a flashlight or a laser and shined it through both glasses, you would be able to see the beam only in the glass with the colloid.

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*Techniques to Separate Solutions*

Common techniques to separate a solution:

\-Distillation: A method of separating solutions that involves boiling a mixture of liquids and collecting the vapor of each liquid as it forms

(Based on varying boiling points between the solute and solvent)

\-Crystallization: A method of separating solutions that involves evaporating the solvent from a solution, causing the solute(s) to crystallize

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*Techniques to Separate Solutions Continued:*

Common technique to separate a solution

\-Chromatography: A method of separating solution in which the solute is separated by density or size of particles

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*Settling Out of Colloids*

Techniques to separate mixtures

\-Centrifuge: Spinning to separate according to density

\-Long-standing: Leaving the mixture to stand over time

\-Boiling/heating: Using heat and electricity to coagulate a colloid

(True solutions don’t do this)

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**Solutions and Solubility**

\-Rate of dissolution: The rate or speed at which a solid dissolves in a liquid

\-Saturated solution: A solution in which the concentration of solute is equal to the maximum concentration predicted from the solute’s solubility

\-Solubility: A property relating to the amount of a solute that will dissolve in a given volume of solvent at a given temperature and pressure

\-Supersaturated solution: A solution in which the concentration of solute is greater than the maximum possible concentration predicted from the solute’s solubility

\-Unsaturated solution: A solution in which the concentration of solute is less than the maximum concentration predicted from the solute’s solubility

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*The Dissolving Process*

1\. Solvent molecules are attracted to solute molecules or ions at the surface of the particles.

(For a solute to dissolve, the molecules or ions that make up the solute must separate from each other. This happens when attractions between the solute molecules or ions and solvent molecules are strong enough to pull the solute particles into solution.)

2\. Solvent molecules surround the solute molecule

3\. Solvent molecules carry the solute molecule into the solution

4\. The solute molecule dissolves in a “like” solvent

(Non-polar substances don’t dissolve in polar solvents like water)

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*Factors that Affect the Rate of Dissolution*

The rate of dissolution describes the rate or speed at which a solid dissolves in a liquid.

It’s affected by:

\-Stirring(Increases the number of collisions

\-Surface area

\-Temperature

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*Solubility*

Solubility is the amount of a solute that will dissolve in a given volume of solvent at a given temperature and pressure.

\-It depends on the solvent

\-Solubility is different from dissolution rate. Solubility is the measure of the amount of solute that dissolves. Dissolution rate is a measure of how fast that solute dissolves.

Solute                                         Solubility(g solute/100 g water

\-Table sugar, C(12)H(22)O(11)   200

\-Table salt, NaCI                         36

\-Aspirin, C(9)H(8(O(4)                0.33

\-Carbon dioxide, CO(2)              0.17

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*Unsaturated, Saturated, and Supersaturated Solutions*

Types of solutions:

\-Unsaturated solution: The concentration of solute is **less than** the maximum concentration predicted from the solute’s solubility

(Ex. Stirring a spoonful of sugar into water. You can still add more sugar to the water and the sugar will still dissolve)

\-Saturated solution: The concentration of solute is **equal to** the maximum concentration predicted from the solute’s solubility; the solute crystallizes at the same rate that it dissolves

(Depends on the solubility of the solute)

(Ex. If you keep adding sugar into the water eventually it won’t dissolve anymore)

\-Supersaturated solution: The concentration of solute is **greater than** the maximum concentration predicted from the solute’s solubility

(Usually made by heating the solution until the solute dissolves, then cooling it very slowly)

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*The Effect of Temperature on Solubility*

Increasing temperature:

\-Increases the solubility of solids and liquids

(Stirring and particle size only affect the rate of dissolution, not the solubility)

\-Decreases the solubility of gasses

(Ex. A soda turning flat on a hot day outside)

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*The Effect of Pressure on Solubility*

Increasing pressure:

\-Increases the solubility of gasses

(There’s more gas molecules on the surface of the liquid)

(Ex. Opening a soda can for the first time)

\-Has little effect on the solubility of solids and liquids

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*Solubility Graphs*

\-Show how solubility changes with temperature

\-Are determined experimentally

\-Predict solubility at a given temperature

\-Show if a solution is saturated, unsaturated, or supersaturated

\-Are different for different solutes

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**Lab: Solubility**

\-Concentrated: A solution that contains a relatively large amount of solute relative to solvent

\-Concentration: A ratio that describes the amount of solute divided by the amount of solvent or solution

\-Dilute: A solution that contain a relatively small amount of solute relative to solvent

\-Dilution: The process of adding more solvent to a solution to decrease the concentration

\-Molarity: The concentration of a solution expressed as the number of moles of solute per liter of solution

\-Stock solution: A concentrated solution of a common reagent used to prepare more diluted solutions to be used in specific reactions

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| Temperature(\*C) | Sugar dissolved(spoonfuls) | Sugar dissolved(grams)\* | | | | | |
|----|----|----|----|----|----|----|----|
| 2 | 8 | 80 | | | | | |
| 24 | 10 | 100 | | | | | |
| 55 | 14 | 140 | | | | | |
| 102 | 25 | 250 | | | | | |

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