C13-15 GROUPS RATES, HEAT CHANGES

Question 1

alkali metals

Answer 1

the name of the metals in group 1 - lithium , sodium , potassium and so on

Question 2

group 1 symbols

Answer 2

li - lithium
Na - sodium
K - potassium

Question 3

reactions of alkali metals with water

Answer 3

metal + water - metal hydroxide + hydrogen

Question 4

lithium and water

Answer 4

lithium floats and bubble vigorously

Question 5

sodium and water

Answer 5

sodium melts into a ball and moves around the surface bubbling vigorously

Question 6

potassium and water

Answer 6

potassium melts into a ball , catches fire and moves around the surface bubbling vigorously

Question 7

group 1 reactivity

Answer 7

reactivity increases as you move down the group

Question 8

explaining group 1 activity

Answer 8

when metals react they lose their outer electrons. further down the group there are more shells of electrons so the outer electrons are less attracted to the nucleus and easier to move

Question 9

halogens

Answer 9

the names given to the non-metals in group 7- fluorine, chlorine , bromine and iodine

Question 10

chlorine

Answer 10

CL2 a pale green gas

Question 11

bromine

Answer 11

BR2 a red brown liquid

Question 12

iodine

Answer 12

l2 a shiny purple black solid

Question 13

reaction of halogens with metals

Answer 13

halogen + metal - metal halide

Question 14

reactions of halogens with hydrogen

Answer 14

halogen + hydrogen - hydrogen halide

Question 15

hydrogen halides

Answer 15

hydrogen halides dissolve in water to form acids, for example hydrogen chloride makes hydrochloric acid

Question 16

chlorine test

Answer 16

chlorine gas turns damp blue litmus red then quickly bleaches it white

Question 17

group 7 activity

Answer 17

reactivity increases as you go up the group

Question 18

explaining group 7 reactivity

Answer 18

when non-metals react they complete their outer shells. further up the group the elements have fewer shells so the nucleus attracts electrons more strongly

Question 19

displacement reactions

Answer 19

reactions in which a more reactive metal displaces a less reactive metal from a salt eg.
copper sulfate + zinc - zinc sulfate + copper
does not work backwards as copper is less reactive than zinc

Question 20

displacement reactions of halogens

Answer 20

a more reactive halogen displaces a less reactive halide ion by taking its electrons

Question 21

redox reactions of halogens

Answer 21

the more reactive halogen oxides the less reactive halide by taking its electrons. the more reactive halogen is reduced

Question 22

noble gases

Answer 22

the name given to the non-metals in group 0 - helium , neon, argon, krypton and xenon

Question 23

melting point of noble gases

Answer 23

they are all gases at room temperature but the melting and boiling point increase down the group

Question 24

reactivity of group 0

Answer 24

the noble gases do not (easily) do any reactions - they are inert

Question 25

explaining reactivity of group 0

Answer 25

when elements react they try to complete their outer shells because group 0 outer shell are already complete , they do not react

Question 26

uses of noble gases

Answer 26

hellium is used in airships because it is inhert and has low density argon is used in fire extinguishers because it is inhert and denser than air mean is used in lighting because it glows red when electricity is passed through it

Question 27

rate of reaction

Answer 27

the rate at which reactants are used up or products are made

Question 28

reactants vs time graphs

Answer 28

starts high and curves downward , decreasing rapidly at first and then more gently. steeper line = faster rate

Question 29

products vs time graph

Answer 29

starts low and curves upwards, increasing rapidly at first and then more gently. steeper line = faster rate

Question 30

measuring rates - reactions that produce gas

Answer 30

collect gas in a gas syringe and measurlthe volume every 30 seconds collect gas over water and measure volume every 30 secs do not reaction on a balance and record the change in mass every 30 secs

Question 31

measuring rates - reactions that go cloudy

Answer 31

do the reaction in a beaker placed on piece of paper with a cross marked on it looking down through the beaker , time how it takes for the crops to disappear

Question 32

collision theory

Answer 32

states for two particles to react they must: collide with each other collide with enough energy to react

Question 33

activation energy

Answer 33

the minimum energy that two particles must have when they collide in order to react

Question 34

effect of concentration on rate

Answer 34

increasing the concentration increase the rate because there are more particles so there are more collisions and more reactions

Question 35

effects of surface area on rate

Answer 35

increasing the surface area (by decreasing particle sizes) in creases the rate by exposing more particles to collisions leading to more collisions and more reactions

Question 36

effect of pressure on rate

Answer 36

increasing the pressure increases the rate because particles are pushed closer together sp they collide more often

Question 37

effect of temperature rate

Answer 37

increasing the temperature increases the rate because particles move faster so they collide more , and collide with more energy to a greater proportion to collisions lead to reactions

Question 38

catalyst

Answer 38

a substance that speeds up a chemical reaction without being used up

Question 39

effects of catalysts on rate

Answer 39

catalysts increase the rate of reaction by reducing the activation energy so that a greater proportion of collisions lead to reactions

Question 40

reaction profile

Answer 40

a graph that shows the changes in energy during a reaction starts with large 'hump' that represents the activation energy

Question 41

effects of catalysts on reaction profiles

Answer 41

the hump representing the activation energy is smaller

Question 42

enzyme

Answer 42

a protein that works as a catalyst to speed up the reactions in our cells

Question 43

enzymes in alcohol production

Answer 43

alcoholic drinks are produced using enzymes found in yeast which catalyst a reaction that urns glucose into ethanol

Question 44

exothermic reactions

Answer 44

a reaction that transfers energy to the surroundings( gets hotter)

Question 45

exothermic reaction examples

Answer 45

``` neutralisation displacement combustion some precipitation respiration ```

Question 46

endothermic reaction

Answer 46

a reaction that absorbs energy from the surroundings

Question 47

endothermic reaction examples

Answer 47

dissolving (most) salts some precipitation photosynthesis

Question 48

exothermic reaction profile

Answer 48

the reactants have more energy than the products so their line on the graph is higher

Question 49

endothermic reaction profile

Answer 49

the reactants have less energy than the products so their line on the graph is lower

Question 50

measuring energy changes

Answer 50

sit a polystyrene beder inside a glass beaker (insulation) measure the starting temperature of the reactants mix the reactants in the polystyrene beaker cover the lid fitted with a thermometer monitor and record the lowest temperature q

Question 51

chemical bonds in reaction.

Answer 51

during chemical reactions , old chemical bonds are broken and new ones are formed

Question 52

breaking bonds

Answer 52

breaking bonds absorbs energy breaking stronger bonds absorbed more energy

Question 53

making bonds

Answer 53

making bonds releases energy making stronger bonds releases more energy

Question 54

energy changes and bond information

Answer 54

the energy change in a reaction is the difference between the energy required to break the old bonds and the energy released by making the ew ones

Question 55

exothermic reactions and bonds

Answer 55

exothermic reactions break weaker bonds and make stronger ones

Question 56

endothermic reactions and bonds

Answer 56

endothermic reactions break stronger bonds and make weaker ones

Question 57

bond strengths

Answer 57

the energy required to break one mole of a particular covalent bond in kj/mol

Question 58

calculating energy changes from bond strength

Answer 58

add up the total strength of old bonds broken and subtract the total strength of new bonds made. a negative answer is a exothermic