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Science 8 > Final > Flashcards

Final Flashcards

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1
Q

What is a chemical bond?

A
  • It is the force of attraction between atoms and ions
  • It occurs when atoms share or transfer electrons
  • Atoms are held together by this
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2
Q

What are valence electrons?

A

Electrons in the outer energy level of an atom

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3
Q

What is a chemical compound?

A
  • When 2 or more elements combine together chemically
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4
Q

What is a chemical formula?

A

Represents compounds

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5
Q

What is a chemical symbol?

A

Represents element

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6
Q

What happens when the same elements combine in different ratios?

A

They may form different compounds

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7
Q

What are the three different compounds?

A

Ionic, Covalent, and Chemical

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8
Q

What is an ionic bond?

A
  • It is the force of attraction that holds together positive and negative ions
  • It forms when atoms of a metallic element give up electrons to atoms of a nonmetallic element
  • Ions are held together by this
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9
Q

What is an ionic compound?

A
  • When atoms transfer electrons to fill outer shell
  • When they transfer they become charged
  • Do not form molecules
  • Contains a metal and nonmetal
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10
Q

What are properties of an ionic compound?

A
  • Strong and rigid (crystal structure)
  • Solids with high melting and boiling points
  • Solids are poor conductors of electricity
  • When in liquid state, they are good conductors of electricity
  • Most easily dissolve in water
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11
Q

What are properties of a chemical compound?

A
  • Consists of fixed ratio of elements

- always has the same composition

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12
Q

What is a covalent bond?

A
  • It is the force of attraction that holds together two atoms that share a pair of electrons
  • Only forms between atoms and nonmetals
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13
Q

Why do covalent bonds form?

A
  • Because they give atoms a more stable arrangement
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14
Q

What is a covalent compound?

A
  • It is what covalent bonds between atoms of different elements form
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15
Q

What are some properties of covalent compounds?

A
  • Has shared electrons
  • poor conductors of electricity
  • Exist as individual molecules rather than crystals
  • has lower melting and boiling points
  • They are gases or liquids at room temperature
  • They do not dissolve in water
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16
Q

Compare properties of polar and nonpolar covalent compounds

A

Polar - When opposites attract

Nonpolar - when similar attract

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17
Q

What is a polar bond?

A

when electrons are not shared equally between the two atoms

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18
Q

What is a nonpolar bond?

A

when electrons are shared equally

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19
Q

What is a hydrogen bond?

A

It is a bond forms between the positive hydrogen end of one water molecule and the negative oxygen end of another water molecule

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20
Q

What is a metallic bond?

A
  • It is the force of attraction between a positive metal ion and the valence electrons it shares with other ions of the metal
  • The positive ions form a lattice-like structure
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21
Q

Why do metallic bonds form?

A

Recall that metals “want” to give up their valence electrons. This means that their valence electrons move freely. The electrons form a “sea” of negative charge surrounding the positive ions

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22
Q

What are the properties of a metallic bond?

A
  • good conductors of electricity

- ductile and malleable

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23
Q

What is an alloy?

A
  • A mixture of a metal with one or more elements
  • solid solution
  • Formed by melting a metal and dissolving the other elements in it
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24
Q

What is brass?

A
  • an alloy of copper and zinc

- Ex: doorknobs, saxophones, and plumbing fixtures

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25
Q

What is stainless steel?

A
  • an alloy of nickel and chronium

- Ex: sinks and eating utensils

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26
Q

What is pure gold?

A
  • most gold jewelry is made up of an alloy of gold, copper, and silver
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27
Q

What is bronze?

A
  • First alloy ever made
  • mixture of copper and tin
  • Ex: statues and coins
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28
Q

What is a chemical reaction?

A

process in which some substances change into different substances

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29
Q

What is an equilibrium?

A

balance between opposing changes or the point at which forward and reverse reactions occur at the same rate

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30
Q

What is a product?

A

Substances that are produced in the reaction

31
Q

What is a reactant?

A

Substances that start a chemical reaction

32
Q

What is a chemical equation?

A

REACTANTS —> PRODUCTS

33
Q

What is a combustion reaction?

A

occurs when a substance reacts quickly with oxygen

34
Q

What is a decomposition reaction?

A

one reactant breaks down into two or more products. This can be represented by the general equation:
AB=A+B

35
Q

What is a replacement reaction?

A

Replacement reactions involve ions. They occur when ions switch places in compounds. There are two types of replacement reactions: single and double

36
Q

What is a synthesis reaction?

A

occurs when two or more reactants combine to form a single product. A synthesis reaction can be represented by the general equation: A+B=C

37
Q

What is an activation energy?

A

It is needed to get chemical reactions started

38
Q

What is an endothermic reaction?

A

it takes more energy to break bonds in the reactants than is released when new bonds form in the products. The word “endothermic” literally means “taking in heat” The general equation for an endothermic reaction is:
Reactants + Energy = Products
(icepack)

39
Q

What is an exothermic reaction?

A

it takes less energy to break bonds in the reactants than is released when new bonds form in the products. The word “exothermic” literally means “turning out heat” The general equation for an exothermic reaction is:
Reactants = Products + Energy
(fire)

40
Q

What is the law of conservation of ENERGY?

A

Energy cannot be created or destroyed

41
Q

How do chemical reactions occur?

A

In chemical reactions, bonds break in the reactants and new bonds form in the products. The reactants and prod- ucts contain the same atoms, but they are rearranged during the reaction. As a result, the atoms are in different combinations in the products than they were in the reactants

42
Q

What are the signs that a chemical reaction has occurred?

A

Change in color & temperature and production of a gas and solid

43
Q

How do you write chemical equations?

A 
hen carbon (C) reacts with oxygen (O2), it produces carbon dioxide
(CO2). The chemical equation for this reaction is:
C+O2 =CO2
44
Q

How do you balance chemical equations?

A
  1. Count the number of each type of atom in reactants and products. Does the same number of each atom appear on both sides of the arrow? If not, the equation is not balanced, and you need to go to step 2.
  2. Add coefficients to increase the number of atoms or molecules of reactants or products. Use the smallest coefficients possible.
  3. Repeat steps 1 and 2 until the equation is balanced.
45
Q

How is the law of conservation of mass to balancing chemical equations related?

A

Why must chemical equations be balanced? It’s the law! Matter cannot be created or destroyed in chemical reactions. This is the law of conservation of mass. In every chemical reaction, the same mass of matter must end up in the products as started in the reactants. Balanced chemical equations show that mass is conserved in chemical reactions

46
Q

How do synthesis reactions occur?

A

occurs when two or more reactants combine to form a single product

47
Q

How do decomposition reactions occur?

A

occurs when two or more reactants break down into to or more products

48
Q

What is a single replacement reaction?

A

occurs when one ion takes the place of another in a single compound. This type of reaction has the general equation:
A + BC = B + AC

49
Q

What is a double replacement reaction?

A

occurs when two compounds exchange ions. This produces two new compounds. A double replacement reaction can be represented by the general equation:
AB+CD=AD+CB

50
Q

How does a combustion reaction occur?

A

occurs when a substance reacts quickly with oxygen

51
Q

How is the law of conservation of energy related to chemical reactions?

A

In any chemical reaction, there is no overall change in the amount of energy. Energy cannot be created or destroyed. This is the law of conservation of energy

52
Q

What are the factors that affects the rates of chemical reactions?

A

temperature of reactants
concentration of reactants
surface area of reactants
presence of catalysts

53
Q

What is concentration?

A

the number of particles of a substance in a given volume

54
Q

What is a catalyst?

A

substance that increases the rate of a chemical reaction but is not changed or used up in the reaction

55
Q

What is distance?

A

it is the length of the route between two points

56
Q

What is frame of reference?

A

refers to something that is not moving with respect to an observer that can be used to detect motion

57
Q

What is motion?

A

a change in position

58
Q

What is a vector?

A

a quantity that includes both size and direction

59
Q

What is speed?

A

It is a measure of how fast or slow something moves. It depends on how far something travels and how long it takes to travel that far. Speed can be calculated using this general formula:
speed = distance/time

60
Q

What is velocity?

A

The measure of both speed and direction

61
Q

What is acceleration?

A

a measure of the change in velocity of a moving object. It shows how quickly velocity changes. Acceleration may reflect a change in speed, a change in direction, or both. Because acceleration includes both a size (speed) and direction, it is a vector

62
Q

How is motion related to the frame of reference?

A

Motion’s perception depends on a person’s frame of reference

63
Q

How do you measure distance?

A
  • Maps
  • Short distances - centimeters
  • Long distances - kilometers
64
Q

How do you represent direction?

A

A vector (the way the arrow points)

65
Q

How do you calculate the speed of a moving object?

A

speed= distance/time

66
Q

How does velocity differ from speed?

A

Speed only tells us how fast or slow an object is moving, but velocity tells us both the measure of speed and direction

67
Q

How do you calculate acceleration?

A

change in velocity over the change in time

68
Q

What is a velocity-time graph?

A
  • it shows how velocity changes over time

- it represents the acceleration of an object

69
Q

What is force?

A

a push or a pull acting on an object

70
Q

What is net force?

A

combined forces acting on an object

71
Q

What is a Newton?

A

SI unit for force

72
Q

What are the examples of force?

A

Gravity and friction

73
Q

Describe how forces combine and affect motion.

A

They combine using net force and they affect motion because they push or pull on an object

Science 8 (2 decks)

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