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8th Grade Science > Chemistry > Flashcards

Flashcards in Chemistry Deck (114):
1

Definition of Matter

has mass; takes up space

2

States of Matter

Solid, Liquid, Gas, Plasma

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Solid

• definite shape
• definite volume
• molecules move slowly (vibrate)

4

Liquid

• indefinite shape
• definite volume

5

Gas

• indefinite shape
• indefinite volume

6

Plasma

• indefinite shape
• indefinite volume
• molecules move really fast
• electrically-charged particles

7

Definition of Shape

a particular form

8

Definition of Volume

amount of space an object occupies (takes up)

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Definition of Mass

amount of matter in an object

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Kinetic Theory of Matter

the theory that all matter is made up of tiny particles that are in constant motion

11

Thermal Expansion

a characteristic of matter causing it to expand when heated and contract when cooled

12

What are particles like in a solid?

• very close together
• vibrate in position

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What are particles like in a liquid?

• close together
• move over each other

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What are particles like in a gas?

• seperate from one another
• move in all directions

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What are particles like in a plasma?

• seperate from one another
• move in all directions
• gas-like

16

What are Crystalline Solids?

solids whose particles are arranged in repeating geometric patterns called crystals (most solids)

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Examples of Crystalline Solids

Rock, Tree

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What are Amorphous Solids?

solids that are not made out of crystals (they slowly change shape)

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Examples of Amorphous Solids

Wax, Play-Doh

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What do liquids do in a container?

they take the shape of the container

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Examples of Liquids

Milk, Soda

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What does a gas do in available space?

it expands and contracts to fill the available space

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Examples of a Gas

Carbon Dioxide, Helium in a tank

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What is the most common form of matter in the universe?

Plasma

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What is most of our solar system's mass composed of?

99% of our solar system's mass is composed of the sun

26

Because of extremely high temperatures, particles in plasma do what?

move more rapidly, collide, and break into smaller charged particles

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Examples of Plasma

Stars (i.e. The Sun), lightning, fire

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Going from a Solid to a Liquid is called...

melting

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Going from a Liquid to a Solid is called...

freezing

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Going from a Gas to a Liquid is called...

condensation

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Going from a Liquid to a Gas is called...

evaporation

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Going from a Solid to a Gas is called...

sublimation

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What is Evaporation?

change of a substance from a liquid state to a gaseous state

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example of Evaporation

a puddle disappears on a sunny day

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What is Condensation?

change of a substance from a gaseous state to a liquid state

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example of Condensation

water on the outside of a cold glass

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What is Sublimation?

a type of evaporation in which a solid changes directly to a gas without going through a liquid state

38

example of Sublimation

dry ice

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What is a Change of State?

the conversion of a substance from one physical form to another

40

What is the difference between Endothermic Changes and Exothermic Changes?

energy is added during endothermic changes. energy is removed during exothermic changes.

41

The Freezing Point and Boiling Point of a substance...

are the same temperature

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What do both Boiling and Evaporation result in?

a liquid changing to a gas

43

Condensation is...

the change of a gas to a liquid // the reverse of evaporation

44

What does Sublimation do?

Sublimation changes a solid directly to a gas

45

During a Change of State, what does the temperature of a substance do?

nothing; the temperature if a substance does not change during a change of state

46

What are Physical Properties?

a characteristic of matter that can be observed or measured WITHOUT CHANGING the identity of the matter

47

examples of Physical Properties

length, mass, volume, density, odor, color, state of matter, flexibility, texture, shape, magnetic

48

What are Chemical Properties?

a characteristic of matter that describes its ABILITY TO CHANGE into NEW MATTER with DIFFERENT properties

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examples of Chemical Properties

flammability, reactivity (can react with another substance to form something new), potential to rust and/or rot

50

What is a Physical Change?

a change of matter from one form to another that affects one or more physical properties

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What is a Chemical Change?

a change that occurs when one or more substances change into new substances with different properties

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It could be a physical change if the substance...

1. Changes shape
2. Dissolves
3. Changes State/Phase
4. Changes color

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What makes something a physical change?

No matter what, the substance is still the same

54

It could be a chemical change if a substance...

1. Changes color because of a chemical reaction
2. Gives off gas/bubbles (forcefully)
3. Burns
4. Forms a new substance
5. Gives off heat
6. Feels cold

55

What is an Exothermic Reaction vs. an Endothermic Reaction?

exothermic reaction - substance gives off heat
endothermic reaction - substance feels cold

56

What is an example of the physical property Solubility?

a flavored drink mix DISSOLVES in water

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What is an example of the physical property Thermal Conductivity?

plastic foam protects you from hot liquid

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What is an example of the physical property Malleability?

aluminum can be FLATTENED into sheets of foil

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What is an example of the physical property Ductility?

copper can be PULLED INTO THIN WIRES

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What is an example of the physical property Odor?

an onion gives off a very distinctive SMELL

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What is an example of the physical property Density?

a golf ball has MORE MASS than a table tennis ball, but the VOLUMES ARE SIMILAR

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When a substance undergoes a physical change, what is not changed? What is changed?

its composition does not change. only a physical property is changed.

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The chemical property that describes the ability of 2 or more substances to combine to form new substances is called...

reactivity

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The ability of a substance to burn is a chemical property known as...

flammability

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An iron nail is reactive with...

oxygen in the air (reaction: rust)

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What is a Characteristic Property of matter?

either a physical or chemical property that scientists use to help identify & classify matter

67

Does a substance always have chemical properties?

yes, even though they are difficult to observe

68

How do you know that baking a cake involves chemical changes?

Baking a cake involves chemical changes because the cake's properties differ from the properties of the ingredients before they were baked.

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Why are chemical changes hard to reverse?

because they change the identity of the substances involved

70

What is the most important question to ask to determine whether a change is physical or chemical?

Did the composition change? (chemical ~ yes; physical ~ no)

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What is the name of the process by which water is broken down into hydrogen and oxygen using an electric current?

electrolysis

72

What are Elements?

They're pure substances made of only 1 kind of atom.

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What are Atoms?

They're tiny structures found in all matter.

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What do most substances contain?

many different atoms. only the elements contain only 1 kind of atom

75

Elements:

1. One kind of atom
2. Pure
3. Seperated in nuclear reactions

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Compounds:

1. 2 or more kinds of atoms chemically bonded
2. Pure
3. Seperated in chemical reactions

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Mixtures:

1. 2 or more elements or compounds physically together
2. Not pure
3. Seperated in physical reactions

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A substance that cannot be seperated into simpler substances by physical or chemical means is...

an element

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What do elements contain only 1 of?

contains only 1 type of atom

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Where can elements be found?

on the periodic table

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What are the 3 major categories of elements?

metals, nonmetals, and metalloids

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examples of elements:

Helium, Iron, Calcium

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A subtance made of 2 or more elements that are chemically combined is...

a compound

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What does a compound have a specific ratio of?

a specific ratio of elements (formula)

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How do the properties of the compound compare to the elements it's made from?

properties of the compound are different than the individual elements it's made from

86

examples of compounds:

Table Salt -> Sodium & Chlorine: NaCl
Sugar (sucrose) -> Carbon, Hydrogen, & Oxygen: C H O
12 11

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A combination of 2 or more substances not chemically combined is...

a mixture

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Do the properties of substances change when forming a mixture?

no; no change in original properties of substances

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Is there a specific ratio of substances when forming a mixture?

no; formed by using any ratio of substances (# of choc. chips in a cookie doesn't matter; it's still a choc. chip cookie)

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examples of mixtures:

Hot Chocolate, Bowl of Cereal, Salt Water

91

This represents the element. While te English name sometimes matches, the Latin name was sometimes used to create this.

Element Symbol

92

This is the most commonly used word for the element.

Element Name

93

Designated by the number of protons in the nucleus, this determines hotizontal placement on the table.

Atomic Number

94

This is determined by the weight of an atom.

Atomic Mass

95

LABEL THE PARTS:
6
C
Carbon
12.01115

1. Atomic Number
2. Element Symbol
3. Element Name
5. Atomic Mass

96

Periodic Table of Elements:

the arrangement of elements according to repeating changes in properties

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How are elements arranged?

Elements are arranged in order of their ATOMIC NUMBER - not atomic weight

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What are vertical columns called, and what do elements in each vertical column have in common?

Vertical columns are called groups or families. There are 18 groups. Elements in each group or family have similar properties.

99

What determines element's properties?

Similar electron arrangements determine element's properties. The number of electrons in the outer energy level determines the chemical properties of that element.

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What are horizontal rows of elements called?

Horizontal rows if elements are called periods.

101

Where are elements that are METALS placed on the periodic table?

All elements to the LEFT of the stair step line are METALS (except hydrogen)

102

What are common properties of metals?

metals are commonly solid at room temperature, shiny, and good conductors of heat & electricity

103

Where are elements that are NONMETALS placed on the periodic table?

All elements to the RIGHT of the stair step line are NONMETALS

104

What are common properties of nonmetals?

Nonmetals are commonly gases or brittle solids at room temperature, and most do not conduct heat & electricity well

105

Where are elements that are METALLOIDS placed on the periodic table?

All elements NEXT TO the stair step line are METALLOIDS

106

What properties do metalloids have?

Metalloids have properties of both metals & nonmetals

107

What elements are TRANSITION ELEMENTS?

All elements in GROUPS 3-12 are TRANSITION ELEMENTS

108

What are transition elements?

Transition elements transition from very metallic to nonmetallic properties

109

Why are elements in group 18 called the noble gases?

They don't react with other elements.

110

What does it mean if an element is synthetic?

It means the element is manmade.

111

Separation of Mixtures:
Evaporation

a mixture is heated until the water changes from a liquid to a gas. the water vapor can be collected & condensed back into liquid form. the reamainin substance has then been separated from the water.

112

Separation of Mixtures:
Sifting/Filtering

a mixture is passed through a screen that separates large particles from small particles. the smaller particles pass through while the larger particles are collected on the screen.

113

Separation of Mixtures:
Weight

a special machine called a centrifuge spins a mixture to separate substances with different masses. the heavier substance is forced to the bottom & the liquid is siphoned off.

114

Separation of Mixtures:
Magnetism

a magnet is used to separate magnetic materials from those that are not magnetic.