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science > year 2 chap 11 > Flashcards

year 2 chap 11 Flashcards

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1
Q

define “matter” please

A
  • anything that has mass & volume
  • the “stuff” of the universe: books, planets, trees, people etc.
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2
Q

define “composition” please

A

the types and amounts of simpler substances that make up a sample of matter

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3
Q

define “properties” please

A

the characteristics that give each substance a unique identity

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4
Q

define “physical properties” and give examples of it

A
  • properties a substance shows by itself without interacting with another substance
  • colour, melting point, density
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5
Q

define “chemical properties” and give examples of it

A
  • properties a substance shows as it interacts with, or transforms into, other substances
  • flammability, corrosiveness
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6
Q

what are the traits of a physical change?

A
  • a change in which no new substances are formed
  • changes can usually be reversed
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7
Q

what are the traits of a chemical change?

A
  • a change in which new substances are formed in the form of elements and compounds
  • changes are not easily reversed
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8
Q

is water turning into ice a physical or chemical change?

A

physical change

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9
Q

what are the substances that react with each other in a chemical change called?

A

reactants

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10
Q

what are the new substances produced in a chemical change called?

A

products

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11
Q

what are the 2 groups that chemical changes can be classified into?

A
  1. reactions where two or more substances chemically combine to form one or more new substances
  2. reactions where a substance breaks down into two or more new substances
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12
Q

the ___ are on the left-hand side of a word equation and the ___ are on the right-hand side of a word equation

A

reactants ; products

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13
Q

what is the law of conservation of mass?

A
  • matter is neither created nor destroyed by chemical reactions or physical changes
  • the mass is the same before and after the reaction
  • the number and type of atoms do not change
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14
Q

what are the different types of chemical reactions?

A

combustion
thermal decomposition
oxidation
neutralisation

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15
Q

what is combustion?

A

a chemical reaction where a substance is heated in the presence of oxygen to form one or more new substances

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16
Q

what is usually given out during combustion?

A

heat and light

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17
Q

what is thermal decomposition?

A

a process where a substance breaks down into two or more simpler substances upon heating

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18
Q

what is oxidation?

A

when a substance gains oxygen and undergoes a chemical change

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19
Q

can oxidation occur in other elements?

A

yes, both metals and non-metals burn in air

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20
Q

what is neutralisation?

A

neutralisation reactions occur when an acid is mixed with an alkali (a.k.a a base) to form water and a salt

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21
Q

what does a “salt” mean?

A

“salt” is a general term for a compound containing an element that is a metal

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22
Q

what ion is responsible for the properties of an acid?

A

hydrogen ions

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23
Q

what are the properties of acids?

A
  • have a sour taste
  • may be dangerous as some acids can burn the skin
  • turns blue litmus paper red
  • reacts with alkalis, metals and carbonates
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24
Q

what is litmus paper used for?

A

litmus paper is used to indicate the acidity or alkalinity of a substance

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25
Q

“base + acid → salt + water”
what is the name given to this reaction?

A

neutralisation

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26
Q

what are the chemical formulas for hydrochloric acid, nitric acid and sulfuric acid?

A

hydrochloric acid: HCl
nitric acid: HNO₃
sulfuric acid: H₂SO₄

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27
Q

what type of salts do hydrochloric acid, nitric acid and sulfuric acid produce?

A

hydrochloric acid: chloride
nitric acid: nitrate
sulfuric acid: sulfate

28
Q

when writing the chemical formula for the salt, write the ___ before the ___

A

cation ; anion

29
Q

acids and metals react to form?

A

a salt and hydrogen gas

30
Q

how to test for hydrogen gas?

A

place a lighted splint near the gas, if hydrogen gas is present, it should extinguish with a pop sound

31
Q

acids and (metal) carbonates react to form?

A

salt, water and carbon dioxide

32
Q

how to test for carbon dioxide?

A

bubble the gas into limewater (calcium hydroxide), if there is carbon dioxide present, white precipitate will form in the water

33
Q

what are the properties of alkalis?

A
  • have a bitter taste
  • have a soapy feel
  • may be dangerous as some alkalis can burn the skin
  • turns red litmus paper → blue
  • reacts w. acids in neutralisation reactions
34
Q

from what number to what number on a pH scale is acidic?

A

0 to 6

35
Q

from what number to what number on a pH scale is alkaline?

A

8 to 14

36
Q

what are neutral substances?

A

neutral substances are neither acids nor alkalis and they are number 7 on the pH scale

37
Q

the formula of an ionic compound is constructed by ____

A

balancing the charges on the positive and negative ions

38
Q

all the positive charges must ___ all the negative charges in an ionic compound

A

be equal to

39
Q

what does a chemical equation show?

A

a chemical equation shows what happens in a chemical reaction

40
Q

what do chemical equations tell us?

A
  • which reactants and products are involved in the reaction
  • the relative amounts of reactants and products;
  • the physical states of the reactants and products of the reaction
41
Q

a balanced chemical equation must contain?

A

equal numbers of atoms of each element on both sides of the equation

42
Q

what are the different state symbols?

A

solid → (s)
liquid → (l)
gas → (g)
aqueous solution → (aq)

43
Q

what does aqueous mean?

A

aqueous means dissolved in water

44
Q

balance the equation “H₂ + O₂ → H₂O”

A

4 hydrogen atoms
2 oxygen atoms

45
Q

acids have ___ ions and alkalis have ___ ions

A

H+ ; OH-

46
Q

higher pH value means ___ and lower pH value means ___

A

stronger alkali ; stronger acid

47
Q

what are some ways we can measure pH value?

A
  • chemical compound called an indicator (universal indicator)
  • pH sensor attached to a data logger
  • pH meter
48
Q

universal indicator changes colour based on the chemical, what colours indicate stronger acid and what colours indicate stronger alkali?

A

acids: dark red to light green
neutral substances: green
alkalis: dark green to violet

49
Q

how do chemical changes occur?

A
  • mixing
  • heating
  • photosynthesis
  • exposure to light
  • interacting with oxygen
  • using an electric current
50
Q

what do chemical changes occurring through mixing mean? give an example please

A
  • when two or more reactants are mixed together, they combine irreversibly to form one or more products, resulting in a chemical change
  • an example would be neutralisation where an acid is mixed with an alkali
51
Q

what is an example of chemical changes occurring through heating?

A

heat or increase in temperature is needed for chemical reactions such as combustion and thermal decomposition

52
Q

what is an example of chemical changes occurring through exposure to light?

A

photosynthesis! in the presence of light, green plants use the chlorophyll in their leaves and take in carbon dioxide and water to produce glucose and oxygen

53
Q

what is an example of chemical changes occurring through interacting with oxygen?

A

rusting as it is an example of oxidation

54
Q

what is an example of chemical changes occurring through using an electric current?

A

electroplating

55
Q

explain electroplating in the context of gold-plating please :)

A
  • an electric current is first passed through a solution containing gold particles then it flows through the solution from one point (gold metal) to another point (silver core)
  • the gold particles coats the sliver core layer by layer and thus a gold-plated object is obtained
56
Q

how can knowledge of chemical reactions help us in our daily lives?

A
  • cooking
  • respiration
  • decay
  • rusting
  • combustion
57
Q

how can knowledge of chemical reactions help us in cooking?

A
  • chemical reactions in food are caused by cooking
  • heat softens the food and improves it flavour
  • cooking also makes it easier for the body to absorb the nutrients in food
58
Q

how can knowledge of chemical reactions help us in respiration?

A
  • glucose molecules react with oxygen to produce carbon dioxide and water
  • energy released allows each cell in an organism to survive and reproduce
59
Q

how can knowledge of chemical reactions help us in rusting?

A
  • in humid climates, large amounts of water vapour is present in the air and rusting occurs rapidly
  • we can prevent rusting by painting, oiling, galvanising (coating iron with a protective layer of zinc) and drying
60
Q

what are the effects of combustion?

A

combustion of fuels can produce air pollutants such as carbon monoxide, sulfur dioxide and oxides of nitrogen

61
Q

what does “acidification of oceans” mean?

A
  • large amounts of carbon dioxide in the atmosphere dissolve in seawater, carbonic acid is formed
  • marine organisms are not able to form new shells or skeletons easily as the carbonate compounds would react with the sea-water
62
Q

what is the charge of elements in group 17?

A

-1

63
Q

what is the charge of elements in group 16?

A

-2

64
Q

what is the charge of elements in group 15?

A

-3

65
Q

what is the charge of elements in group 13?

A

+3

66
Q

what is the charge of elements in group 2?

A

+2

67
Q

what is the charge of elements in group 1?

A

+1

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