beaker breaker!! 1.)when two atoms are touching based on the activity yesterday that means it is...
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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 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
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
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
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.
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