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Science topics excluding forces and thermal energy > Chemical changes > Flashcards

Chemical changes Flashcards

1
Q

What is chemical change?

A

Process where new substances of different chemical properties are formed

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2
Q

What are the common attributes of chemical reactions? (PIECOLT)

A
  1. Bubbles of gas are formed (effervescence)
    [New odour or smell noticed]
  2. The change is difficult or impossible to reverse
  3. A new colour appears
  4. Thermal or light energy is given off/ absorbed
  5. A solid material (precipitate) is formed in a solution
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3
Q

What law do chemical changes obey?

A

The law of conservation of mass

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4
Q

What is combustion?

A

AKA burning

  • Reaction with oxygen to release energy
  • Involves oxygen as a reactant
  • Releases energy, (usually thermal)
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5
Q

What is oxidation?

A

-Addition of oxygen to a substance
- No energy is released
- Can cause rusting

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6
Q

What is decomposition thermal?

A
  • Involves the breakdown of a compound into simpler substances through strong heating.
  • Requires an activation energy
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7
Q

What is decomposition electrolysis?

A
  • Involves the breakdown of a compound into simpler substances
  • through passing of electricity
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8
Q

What is neutralisation?

A

Acid + Alkali = Salt + water

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9
Q

What is photosynthesis?

A
  • Process by which green plants transform light energy into chemical potential energy
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10
Q

What is respiration?

A

Process by which cells in living organisms get energy

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11
Q

What is the law of conservation of mass?

A
  • Atoms are not created or destroyed in a reaction. They are only rearranged. Mass is conserved.
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12
Q

What is precipitation?

A
  • `When 2 solutions are mixed, a solid may form
  • This white chalkiness is called white precipitation,
    It involves the formation of a solid when 2 solutions are mixed
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13
Q

What do elements in the same group have in common in terms of valence electrons?

A

They all have the same number of valence electrons

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14
Q

What do elements of the same group have in common in terms of chemical properties?

A
  • Since chemical properties of elements depend on the number of valence electrons an element has and elements in the same group have the same number of valence electrons, elements in the same group have similar chemical properties.
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15
Q

What are the unique features of noble gases? (MSVGFB)

A
  • They are monoatomic elements
  • They are relatively stable chemically
  • They are in group 18 and have 8 valence electrons
  • Since their valence shell is full
  • They do not bond with other atoms
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16
Q

What is chemical bonding?

A
  • It is the electrostatic force of attraction
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17
Q

What is involved in chemical changes?

A
  • Only valence electrons are involved in chemical changes (to become stable)
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18
Q

What do the formation of chemical bonds depend on?

A
  • Atoms forming chemical bonds depend on the electronic configuration of atoms
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19
Q

What type of ions will bond?

A
  • Only opposite ions will bond (ionic transfer)
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20
Q

What is an ionic bond?

A
  • It is the electrostatic force of attraction between oppositely charged ions
  • Metal atoms transfer electrons to the non metal atoms
  • 1 valence will transfer 1 electron
  • 2 valence will transfer 2 electrons
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21
Q

Are metals and non metals negatively or positively charged?

A
  • Non metals are negatively charged
  • Metals are positively charged
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22
Q

What is the order in which the chemicals are written in for ions?

A

The formula for a positive ion is written before that of a negative ion
- EG: Sodium sulfate is Na2S not SNa2

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23
Q

What is a covalent bond?

A

It is the electrostatic force of attraction between the shared pair of electrons and the positive nuclei of the 2 atoms
- this bond is formed when 2 non-metal atoms share electrons

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24
Q

What are the types of covalent bonds?

A
  • SINGLE BOND
    — 1 pair of shared electrons
  • DOUBLE BOND
    — 2 pairs of shared electrons
  • TRIPLE BOND
    — 3 pairs of shared electrons
  • Refer to note called BOOKMARKED [CC] pg 1 titled Slide 24 for more info
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25
Q

What are the 2 different forms for the drawing of covalent bonds?

A
  1. Dot can cross
    - Involves the usage of dots and crosses
  2. Structural formula
    - Involves the usage of lines
  • Refer to note called BOOKMARKED [CC] pg 1 titled Slide 25 for more info
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25
Q

What is the prefix as the number of atoms in each second element in a compound changes?

A
  1. Mono
  2. Di
  3. Tri

*reminder that this only applies for covalent compounds

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26
Q

What should be kept in mind as we write a chemical equation?

A

Remember to balance both sides of the equation.

27
Q

Acids + Reactive metals =

A

Salt + Hydrogen gas

28
Q

What is the test for hydrogen gas?

A

Placing a lighted a splint in a test tube with hydrogen gas (Gas will extinguish a lighted splint with a ‘pop’ sound)

29
Q

Acids + Metal carbonates =

A

Salt + Carbon dioxide + water

30
Q

What is the test for carbon dioxide?

A

Bubble carbon dioxide into limewater [Ca (OH)2], if there is carbon dioxide, a white precipitate will form (ppt)

31
Q

What are the common attributes of alkali?

A
  • tend to be foam or soapy in nature
  • soap detergent
  • Sodium hydroxide, ammonia, calcium hydroxide
32
Q

What is an exothermic reaction?

A
  • When the solution becomes warm (test tube feels warm)
  • Because energy is given out
33
Q

Use of indicators:

A

To tell if a solution is acidic or alkali

34
Q

Another name for universal indicator?

A

PH indicator

35
Q

What is the range of numbers on a pH scale

A

0-14

36
Q

What colour and pH level is the most acidic substance?

A
  • pH level 1
  • Colour is dark red
37
Q

What colour and pH level is the most alkaline substance?

A
  • pH level 14
  • Colour is dark purple
38
Q

What are the colour changes in the pH scale?

A

Dark red, red, orange, yellow, light green, dark green, blue, dark blue, purple, dark purple

39
Q

What is a salt?

A

It is a substance formed when a metallic ion replaces one or more hydrogen ions of an acid

40
Q

What is the harmful effect of burning

A

Burning produces air pollutants

41
Q

State 2 other harmful effects of chemical change

A
  1. Rusting- weakening of a steel structure (oxidation - rusting)
  2. Decay of food - due to bacteria, yeasts and moulds
42
Q

How to tell when its a alkali and when its an acid?

A
  1. Xide- Alkali
  2. Ic- Acid
43
Q

What are the formulas for Magnesium ribbons, calcium carbonate powder and potassium hydroxide solution?

A
  1. Mg
  2. CaCO3
  3. KOH
44
Q

How do you write out N2O?

A

Dinitrogen monoxide

45
Q

What is special about the word equations for iron and copper?

A

The stating of charge is required (same for other transition metals)

46
Q

What does the charge decide?

A

The number of atoms in each element

47
Q

When drawing dot and cross diagram, which element is always cross?

A

Base element

48
Q

In the electronic configuration, the first shell always has __ electrons

A

2

49
Q

What are the diatomic molecules in the periodic table?

A
  1. Oxygen
  2. Hydrogen
  3. Nitrogen
  4. Chlorine
  5. Bromine
  6. Iodine
  7. Fluorine
  • 4 to 7 are halogens (grp 17)
50
Q

What is the formula for ammonium ion/ ammonia

A

Ammonium ion
= NH4^ +

Ammonia
= NH3

51
Q

What is the formula for Methane?

A

CH4

52
Q

What is the formula for Hydroxide ion?

A

OH^ -

53
Q

What is the formula for Nitrate ion?

A

NO3^ -

54
Q

What is the formula for Copper (II) ion?

A

Cu^2+

55
Q

What is the formula for Iron (II) ion?

A

Fe^2+

56
Q

What is the formula for Sulfate ion?

A

SO4^2-

57
Q

What is the formula for Carbonate ion?

A

CO3 ^ 2-

58
Q

What is the formula for sodium carbonate?

A

Na2CO3

59
Q

What is the formula for Calcium hydroxide?

A

Ca (OH)2

60
Q

What is the formula for Sodium hydroxide?

A

NaOH

61
Q

What is the formula for Sulfuric acid

A

H2SO4

62
Q

What is the formula for Calcium carbonate?

A

CaCO3

63
Q

Why don’t noble gases bond with other atoms?

A

Noble gases are unreactive

64
Q

If a polyatomic ion (more than 2 atoms in the ion) occurs more than once in a formula, it must be

A

Enclosed in brackets

65
Q

potassium hydroxide sol vs Calcium carbonate… which one to pick when cleaning hydrochloric acid?

A
  1. Not potassium hydroxide. Why? even tho it is an alkali and can be use to neutralise HCl, if it spills on the floor both are colour less so u cant see them and clean them up properly.
  2. Choose calcium carbonate. When reacting w HCl it produces calcium chloride, H2O and CO2 which are not harmful.

Science topics excluding forces and thermal energy (1 decks)

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