Beaker Breaker!!

1.)When two atoms are touching based on the activity yesterday that means it is considered a___________

2.)What do the small numbers (subscripts) represent in H2O?

Chapter 2 Properties Chapter 2 Properties of Matterof Matter

Chapter 2 Properties Chapter 2 Properties of Matterof Matter

2-1 Classifying Matter2-1 Classifying Matter

Objectives1. Classify pure substances as

elements or compounds2. Describe the characteristics of an

element and the symbols used to identify elements

3. Describe the characteristics of a compound

Pure Substances• Matter that always has exactly the same

composition is classified as a pure substance.• Every sample of a given substance has the

same properties because a substance has a fixed, uniform composition.

• Ex – Table Salt (Na) and sugar(C6H12O6)

• Can be classified into elements and compounds

Elements• Element is a substance that cannot be

broken down into simpler substances.• Atoms are the smallest particle of an

element.• An element has a fixed composition

because it contains only one type of atom.

Examples of Elements• Most are solids – Aluminum (Al)

• Some are gases – Carbon (C)

• Two are liquids are room temperature – Bromine (Br) and Mercury (Hg)

Symbols for Elements• The first letter is always

capitalized• If there is a second letter it is not

capitalized -Na (sodium)• If the symbol contains only one

letter, it is always capitalized - C

Compounds• A compound is a substance that is

made from two or more simpler substances and can be broken down into those simpler substances.

• A compound always contains two or more elements joined in a fixed proportion.

• Ex. Water – H2O

Mixtures• The properties of a mixture can

vary because of composition of a mixture is not fixed.

• Example - Salsa

Beaker Breaker!!

1.) Can an element or a compound be broken down into simpler parts?

2.) What is an example of a pure substance?

3.)What are the building blocks of elements?

What is a mixture?• Variable combination of 2 or

more pure substances.

Heterogeneous Homogeneous

What is the difference between a

homogeneous and a heterogeneous

substance?

•Heterogeneous: substance whose composition is not uniform throughout……always a mixture

What is the difference between a homogeneous and a heterogeneous substance?

•Homogeneous: substance that is uniform (same) in its composition

A mixture may be…•Homogeneous•(same)

•Heterogeneous•(different)

Solutions• When substances dissolve and form a

homogeneous mixture, the mixture that forms is called a solution.

• Ex: tap water and windshield wiper fluid

• Light passes through liquid solutions without being scattered in all directions

Suspensions• A heterogeneous mixture that

separates into layers over time is called a suspension.

• Ex: Shaking a jar of sand and water

Colloids• A colloid contains some particles that

are intermediate in size between the small particles in solution and the larger particles in a suspension.

• Fog is a colloid of water droplets in air• Scattering of light is a property of a

colloid

Beaker Breaker!!

1.) When substances dissolve and form a homogeneous mixture, the mixture that forms is called a___________.

2.) Is fog an example of a colloid or a suspension?

3.) A heterogeneous mixture that separates into layers over time is called a_____________

Solutions Cont.• Recall that a solution is a

homogeneous mixture of two or more substances

• Two components1. Solute2. Solvent

Solutes• A solute is a substance whose

particles are dissolved in a solution.

Solvents• The substance in which the solute

dissolves is called the solvent.

Example• Seawater solution• Solute = salt• Solvent = water

Beaker Breaker!!

1.) A__________________is a substance whose particles are dissolved in a solution.

2.) The substance in which the solute dissolves is called the ___________________.

3.) sugar in water – circle the solvent and underline the solute

2-2 Physical Properties• A physical property is any

characteristic of a material that can be observed or measured without changing the composition of the substances in the material

Examples of physical properties

1. Viscosity2. Conductivity3. Malleability4. Hardness5. Melting Point6. Boiling Point7. Density

Viscosity• The tendency of a liquid to keep

from flowing – resistance to flowing is called viscosity.

• Example - Honey

Conductivity• A material’s ability to allow heat to

flow is called conductivity• Example : Metals = high

conductivity or also know as conductors

• Stirring soup with a metal soup verses wooden spoon

Malleability• Malleability is the ability of a solid

to be hammered without shattering.

• Ex gold and aluminum

Hardness• One way to compare the hardness

of two materials is to see which of the materials can scratch the other.

• Ex: Kitchen knife (stainless steel) scratching copper

Melting Point and Boiling Point

• The temperature at which a substance changes from a solid to a liquid is its melting point.

• The temperature at which a substance boils is its boiling point

• Ex: Water at 0 degrees Celsius and 100 degrees Celsius

Density• Density can be used to test the purity

of a substance.

• Density = Mass VolumeEx: Silver coin density = 9.9g/cm3

Actual density of silver = 10.5g/cm3

Coin is not pure silver

Beaker Breaker!!1.) Name one of the seven physical

properties________________2.) Which physical property is defined as a

material’s ability to allow heat to flow?

3.) Aluminum and Gold are examples are what physical property?_____________

Using Properties to Separate Mixtures

1. Filtration is a process that separates materials based on the size of their particles

2. Distillation is a process that separates the substances in a solution based on their boiling points.

Recognizing Physical Changes

• A physical change occurs when some of the properties of a material change, but the substances in the material remains the same.

• Ex: slowly heating butter in a pan –changes from solid to liquid, but the substance in the butter remains the same.

• Slicing a tomato• Crumpling a piece of paper

Chemical Properties• A chemical property is any ability

to produce a change in the composition of matter.

• Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.

Examples1. Flammability is a material’s

ability to burn in the presence of oxygen.

Ex. Gasoline and paper

Reactivity• The property that describes how readily

a substance combines chemically with other substances is reactivity.

• Example – gases in airOxygen is highly reactiveNitrogen has a low reactivity- Rust is another example

Recognizing Chemical Changes

• A chemical change occurs when a substance reacts and forms one or more new substances.

Examples: cake baking in oven leaves on trees change color food digested in your stomach

Three common types of evidence

1. Change in color

2. The production of a gas

3. The formation of a precipitate

A change in color• Ex: silver tarnishing a match burning then turning

black and shrivels

Production of a Gas• Ex: Combining vinegar and baking

soda – bubbles of carbon dioxide form

Formation of a Precipitate

• Any solid that forms and separates from a liquid mixture is called a precipitate.

• Ex: when acid is added to milk, proteins in the milk undergo a chemical change that alters their structure, causing them to stick together in clumps

Is a change chemical or physical?

• When matter undergoes a chemical change, the composition of matter changes.

• When matter undergoes a physical change, the composition of the matter remains the same.

Beaker Breaker!!1.) What is one of the three common types of evidence

of a chemical change?

2.) Any solid that forms and separates from a liquid mixture is called a__________

3.) Gasoline and paper is an example of what chemical property?