year 2 chap 11

Question 1

define “matter” please

Answer 1

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

Question 2

define “composition” please

Answer 2

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

Question 3

define “properties” please

Answer 3

the characteristics that give each substance a unique identity

Question 4

define “physical properties” and give examples of it

Answer 4

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

Question 5

define “chemical properties” and give examples of it

Answer 5

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

Question 6

what are the traits of a physical change?

Answer 6

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

Question 7

what are the traits of a chemical change?

Answer 7

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

Question 8

is water turning into ice a physical or chemical change?

Answer 8

physical change

Question 9

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

Answer 9

reactants

Question 10

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

Answer 10

products

Question 11

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

Answer 11

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

Question 12

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

Answer 12

reactants ; products

Question 13

what is the law of conservation of mass?

Answer 13

• 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

Question 14

what are the different types of chemical reactions?

Answer 14

combustion
thermal decomposition
oxidation
neutralisation

Question 15

what is combustion?

Answer 15

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

Question 16

what is usually given out during combustion?

Answer 16

heat and light

Question 17

what is thermal decomposition?

Answer 17

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

Question 18

what is oxidation?

Answer 18

when a substance gains oxygen and undergoes a chemical change

Question 19

can oxidation occur in other elements?

Answer 19

yes, both metals and non-metals burn in air

Question 20

what is neutralisation?

Answer 20

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

Question 21

what does a “salt” mean?

Answer 21

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

Question 22

what ion is responsible for the properties of an acid?

Answer 22

hydrogen ions

Question 23

what are the properties of acids?

Answer 23

• 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

Question 24

what is litmus paper used for?

Answer 24

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

Question 25

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

Answer 25

neutralisation

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

cation ; anion

Question 29

acids and metals react to form?

Answer 29

a salt and hydrogen gas

Question 30

how to test for hydrogen gas?

Answer 30

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

Question 31

acids and (metal) carbonates react to form?

Answer 31

salt, water and carbon dioxide

Question 32

how to test for carbon dioxide?

Answer 32

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

Question 33

what are the properties of alkalis?

Answer 33

- 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

Question 34

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

Answer 34

0 to 6

Question 35

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

Answer 35

8 to 14

Question 36

what are neutral substances?

Answer 36

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

Question 37

the formula of an ionic compound is constructed by ____

Answer 37

balancing the charges on the positive and negative ions

Question 38

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

Answer 38

be equal to

Question 39

what does a chemical equation show?

Answer 39

a chemical equation shows what happens in a chemical reaction

Question 40

what do chemical equations tell us?

Answer 40

- 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

Question 41

a balanced chemical equation must contain?

Answer 41

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

Question 42

what are the different state symbols?

Answer 42

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

Question 43

what does aqueous mean?

Answer 43

aqueous means dissolved in water

Question 44

balance the equation "H₂ + O₂ → H₂O"

Answer 44

"2H₂ + O₂ → 2H₂O" -------------------------- 4 hydrogen atoms 2 oxygen atoms

Question 45

acids have ___ ions and alkalis have ___ ions

Answer 45

H+ ; OH-

Question 46

higher pH value means ___ and lower pH value means ___

Answer 46

stronger alkali ; stronger acid

Question 47

what are some ways we can measure pH value?

Answer 47

- chemical compound called an indicator (universal indicator) - pH sensor attached to a data logger - pH meter

Question 48

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

Answer 48

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

Question 49

how do chemical changes occur?

Answer 49

- mixing - heating - photosynthesis - exposure to light - interacting with oxygen - using an electric current

Question 50

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

Answer 50

- 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

Question 51

what is an example of chemical changes occurring through heating?

Answer 51

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

Question 52

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

Answer 52

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

Question 53

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

Answer 53

rusting as it is an example of oxidation

Question 54

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

Answer 54

electroplating

Question 55

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

Answer 55

- 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

Question 56

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

Answer 56

- cooking - respiration - decay - rusting - combustion

Question 57

how can knowledge of chemical reactions help us in cooking?

Answer 57

* 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

Question 58

how can knowledge of chemical reactions help us in respiration?

Answer 58

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

Question 59

how can knowledge of chemical reactions help us in rusting?

Answer 59

* 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

Question 60

what are the effects of combustion?

Answer 60

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

Question 61

what does "acidification of oceans" mean?

Answer 61

* 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

Question 62

what is the charge of elements in group 17?

Answer 62

-1

Question 63

what is the charge of elements in group 16?

Answer 63

-2

Question 64

what is the charge of elements in group 15?

Answer 64

-3

Question 65

what is the charge of elements in group 13?

Answer 65

+3

Question 66

what is the charge of elements in group 2?

Answer 66

+2

Question 67

what is the charge of elements in group 1?

Answer 67

+1