Exothermic and endothermic reactions: Flashcards
(125 cards)
1
Q
Key Points
A
2
Q
When a chemical reaction happens
A
energy is transferred to or from the surroundings.
3
Q
When energy is transferred to the surroundings
A
this is called an exothermic reaction and usually feels hot.
4
Q
When energy is taken in from the surroundings
A
this is called an endothermic reaction and usually feel cold.
5
Q
Can you think of any everyday reactions that either release energy into the surroundings or absorb it?
A
6
Q
A
7
Q
A
8
Q
Show answer
A
9
Q
Science flasks
A
10
Q
Video
A
11
Q
Watch this video about different
A
12
Q
exothermic
A
13
Q
and
A
14
Q
endothermic
A
15
Q
reactions.
A
16
Q
A
17
Q
While you’re watching
A
look out for the different household items which can be used for exothermic and endothermic reactions.
18
Q
A
19
Q
A
20
Q
A
21
Q
Video Transcript
A
22
Q
What happened to the temperature when citric acid and bicarbonate of soda were mixed?
A
23
Q
A
24
Q
A
25
Show answer
26
Exothermic reactions
27
Glowsticks
28
Image caption
29
Glowsticks are an example of an exothermic reaction
30
Exothermic reactions are
31
chemical reactions
32
which release energy from the chemicals into the surroundings. This energy is usually released as heat
so the surroundings get hotter. Handwarmers are an example of an exothermic reaction. They release heat into their surroundings.
33
34
However
exothermic reactions don't always release heat
35
36
Example of an exothermic reaction
37
Image gallerySkip image gallery
38
Sodium hydroxide solution is poured into a beaker of hydrochloric acid. The thermometer shows the initial temperature
which is room temperature
39
Image caption
40
1. Sodium hydroxide solution is poured into a beaker of hydrochloric acid. The thermometer shows the initial temperature
which is room temperature.
41
42
The beaker now contains sodium chloride and water
and the thermometer is showing a rise in temperature
43
Image caption
44
2. The beaker now contains sodium chloride and water. The temperature on the thermometer has risen
meaning it is an exothermic reaction.
45
46
1 of 2
47
48
49
Previous image
50
51
Next image
52
Slide 1 of 2
Sodium hydroxide solution is poured into a beaker of hydrochloric acid. The thermometer shows the initial temperature
53
End of image gallery
54
Respiration is a chemical process that takes place inside the cells of all living organisms. Respiration releases energy for the organism to use to stay alive.
55
56
Is respiration an exothermic reaction or an endothermic reaction?
57
58
59
Show answer
60
Endothermic reactions
61
Plants soaking up sunlight
62
Image caption
63
Plants use endothermic reactions to absorb sunlight during photosynthesis
64
Endothermic reactions absorb energy from the surroundings. This energy is usually absorbed as heat
so the surroundings get colder.
65
66
67
Photosynthesis
68
is an endothermic reaction because plant leaves absorb light energy.
69
70
Thermal decomposition
71
reactions are endothermic because they absorb energy when the chemicals are heated.
72
Example of an endothermic reaction
73
Image gallerySkip image gallery
74
Sodium carbonate powder is tipped into a beaker of ethanoic acid which contains a thermometer showing room temperature
75
Image caption
76
1. Sodium carbonate powder is tipped into a beaker of ethanoic acid. The thermometer shows the initial temperature reading which is room temperature.
77
78
The beaker now contains sodium ethanoate
water and carbon dioxide
79
Image caption
80
2. The beaker now contains sodium ethanoate
water and carbon dioxide. The temperature on the thermometer has fallen
81
82
1 of 2
83
84
85
Previous image
86
87
Next image
88
Slide 1 of 2
Sodium carbonate powder is tipped into a beaker of ethanoic acid which contains a thermometer showing room temperature
89
End of image gallery
90
When ammonium chloride powder is mixed with barium hydroxide powder and stirred
a chemical reaction takes place. The temperature drops to –14°C.
91
92
True or false? This is an exothermic reaction.
93
94
95
Show answer
96
Working Scientifically
97
Exothermic and endothermic reactions that occur at room temperature in the science lab can be investigated using a thermometer.
98
99
Here are some things to remember when conducting this type of experiment.
100
101
102
Show more
103
When investigating exothermic and endothermic reactions
it is important to minimise sources of error to make sure that the results are
104
accurate
105
and
106
repeatable
107
.
108
109
A sign which says 'remember'
110
Accuracy can be improved by getting a precise value for the room temperature before the experiment begins
and using an insulated polystyrene cup to stop unwanted heat transfers.
111
112
An insulated cup with a lid
113
Image caption
114
An insulating polystyrene cup with a lid will make results more accurate
115
Results are repeatable if they are similar to each other when the experiment is repeated.
116
117
Sometimes one result from a set of repeat measurements is very different from the rest of the results. This is called an
118
outlier
119
or an
120
anomalous result
121
.
122
123
Usually it is best to ignore an outlier.
124
125
Find out more about accuracy and repeatability in this guide.
