Prática de Shadowing: Exploring the pH Scale - Aprenda a falar inglês com vídeo
Escolha um modo de prática
Cada modo abre uma sala de prática em tela cheia.
99 frases
Se as frases estiverem muito curtas ou longas, clique em Edit para ajustá-las.
1
Lemon juice is acidic.
2
Pure water is neutral.
3
Many cleaning products are alkaline.
4
But what do these terms mean and how do we measure the difference?
5
The pH scale gives us a way to compare them and each step represents a much bigger change than you might expect.
6
You'll see the pH scale displayed in several ways as colored bars, a dial, droplets, and a digital display.
7
Each shows the same information in a different layout.
8
For a closer look we'll use this vertical scale and work through the examples one by one.
9
pH describes how acidic or alkaline a water -based solution is.
10
The familiar scale runs from 0 to 14 although some solutions fall outside this range.
11
At 25 degrees Celsius, 7 is neutral.
12
Below 7 is acidic.
13
Above 7 is alkaline, or basic.
14
To understand what these numbers mean, we need to look at the particles in the solution.
15
Water contains tiny amounts of hydrogen ions and hydroxide ions.
16
Ions are particles with an electrical charge.
17
In a neutral solution, hydrogen ions and hydroxide ions have equal concentrations.
18
An acidic solution has a higher concentration of hydrogen ions than hydroxide ions.
19
In an alkaline solution, the reverse is true.
20
The lower the pH, the higher the hydrogen ion concentration.
21
Each whole step represents a tenfold change.
22
A solution at pH 3 has 10 times the hydrogen ion concentration of 1 at pH 4.
23
Compared with a solution at pH 5, it has 100 times the hydrogen ion concentration.
24
Move towards higher pH numbers, and hydrogen ion concentration decreases tenfold with each step.
25
This makes pH a logarithmic scale.
26
A difference of two pH units represents a hundred -fold change in hydrogen ion concentration.
27
A difference of three units represents a thousand -fold change.
28
The colors help us read the scale.
29
They represent the colors produced by Universal Indicator, a mixture of dyes that changes color with pH.
30
Universal Indicator generally shows reds and oranges in acidic solutions, green near neutral, and blues or purples in alkaline solutions.
31
These are indicator colors, not necessarily the colors of the substances themselves.
32
A calibrated pH meter measures pH electronically and displays a numerical reading.
33
Let's work through the examples, starting at the acidic end.
34
Their positions are approximate.
35
The actual pH depends on the particular sample and its concentration.
36
To test an unknown substance, we use suitable equipment.
37
Never taste or touch.
38
Battery acid appears at the extreme acidic end of our chart.
39
Lead -acid car batteries contain sulfuric acid, which takes part in the reactions that produce an electric current.
40
Battery acid is highly corrosive and can cause severe chemical burns.
41
Next is stomach acid.
42
Your stomach contains hydrochloric acid, which creates the acidic conditions needed by an enzyme called pepsin.
43
Pepsin helps digest proteins in food.
44
The acid also helps kill many swallowed microbes, while a protective mucus barrier helps shield the stomach lining.
45
Lemon juice commonly has a pH around 2 to 3.
46
Much of its acidity comes from citric acid
47
which gives lemons their familiar sour taste grapefruit juice is also
48
acidic commonly around ph3 it contains citric acid too the exact ph varies between fruits and can change as they ripen
49
tomato ketchup is usually around ph4 acids from the tomatoes
50
and added vinegar contribute to its tangy flavor the acidic conditions
51
also help limit the growth of many microorganisms black coffee is commonly around pH 5.
52
Several dissolved acids contribute to its acidity, and the exact pH depends on the beans and how the coffee is brewed.
53
A substance does not have to taste like lemon juice to be acidic.
54
Fresh milk is only slightly acidic, usually around pH 6 .5.
55
As milk sours, bacteria convert milk sugar into lactic acid.
56
This increases hydrogen ion concentration and lowers the pH.
57
At pH 7, we reach our neutral reference, pure water at 25 degrees Celsius.
58
Its hydrogen ion and hydroxide ion concentrations are equal.
59
Neutral does not mean these ions are absent.
60
Both are present in equal, very small amounts.
61
Moving past 7, we enter the alkaline region.
62
Seawater is slightly alkaline, with surface ocean water averaging around pH 8 .1.
63
When the ocean absorbs carbon dioxide, chemical reactions increase hydrogen ion concentration and lower the pH.
64
This is called ocean acidification.
65
The term describes the decrease in pH, even though seawater remains alkaline.
66
Around pH 9, we find borax dissolved in water.
67
Borax is a mineral used in some cleaning products.
68
Its solution is alkaline, with a typical pH around 9 .2.
69
Milk of magnesia is around pH 10 to 11.
70
Despite its name, it is not dairy milk.
71
It contains magnesium hydroxide and is used as an antacid.
72
The magnesium hydroxide reacts with excess stomach acid, reducing acidity.
73
Household ammonia solution is often around pH 11.
74
It consists of ammonia dissolved in water and is used in some cleaning products to help remove grease.
75
Ammonia must never be mixed with bleach because the reaction can release dangerous gases.
76
At pH 12, our example is dilute lye, a sodium hydroxide solution.
77
This shows that even a relatively dilute solution can be highly alkaline.
78
Its pH depends on how much sodium hydroxide is dissolved in a given volume of solution.
79
Household chlorine bleach is another highly alkaline example, placed here near pH 13.
80
It contains sodium hypochlorite and is formulated to remain alkaline.
81
Its actual pH varies between products.
82
Bleach should never be mixed with other cleaners.
83
At the alkaline extreme, some drain cleaners contain concentrated sodium hydroxide.
84
This reacts with fats and helps break down organic material in blocked pipes.
85
Like battery acid at the opposite end of the scale, these products can cause severe chemical burns.
86
Now compare two solutions, one at pH 3 and another at pH 5.
87
Which has the higher hydrogen ion concentration?
88
The solution at pH 3.
89
How much higher?
90
100 times.
91
There are two steps between them, and each represents a factor of 10.
92
There's one more distinction to remember.
93
A low pH does not automatically mean an acid is classified as a strong acid.
94
In chemistry, acid strength describes how readily an acid releases hydrogen ions in water.
95
The pH also depends on its concentration.
96
Citric acid is classified as a weak acid, even though lemon juice has a low pH.
97
The pH scale helps us describe and compare solutions, from the food we eat to seawater and household products.
98
At 25 degrees Celsius, below 7 is acidic,
99
7 is neutral, and above 7 is alkaline and every whole step represents a tenfold change in hydrogen ion concentration.
Baixar aplicativo
Tudo o que você precisa para falar fluentemente
Pronúncia com IANota em cada frase
Prática de IPADomine cada som
VocabulárioMonte seu banco de palavras
Jogo de vocabulárioAprenda brincando
Mesmo canal
A22
Importance of Farms
KidsDaily Conversation
B1Simple Machines – Screws
KidsDaily Conversation
B12
All About Mosses
Daily ConversationUniversity Students
A28
Using Rocks and Minerals
KidsDaily Conversation
B11
Interactions in Ecosystems – Wetlands
KidsDaily Conversation
B11
Temperate Climates
KidsDaily Conversation
A22
Sound, Vibrations and Sound Waves
KidsDaily Conversation
B26
The Earth's Atmosphere
Daily ConversationHigh School Students
A24
All About Magnets
KidsDaily Conversation
B2100
Pollination in a Minute
Daily ConversationHigh School Students
B16
Earth Water Sources – Streams and Rivers
KidsDaily Conversation
B11
Electric Charge
Daily ConversationHigh School Students
B16
Changing States of Matter
KidsDaily Conversation
B13
Animal Structures for Catching Prey
KidsDaily Conversation
A210
Chew Chew Train – Food's Journey Through Your Body!
KidsDaily Conversation
C11
Ferns Grew Up. Why Couldn’t They Move On?
Daily ConversationHigh School Students
A22
Explore Tropical Rainforests with TESS!
KidsDaily Conversation
B18
Water Pollution and How We Can Reduce It!
TeensDaily Conversation
A21
Magnet Race Car!
KidsDaily Conversation
B12
Bulbs Arranged in Parallel – Brightness of Bulbs
Daily ConversationHigh School Students
FOR YOU
Vídeo recomendado
B21
166 frases
WHAT ARE NATURAL NUMBERS?
Daily ConversationHigh School Students
B12
36 frases
Identifying Chemical Properties
Daily ConversationHigh School Students
B14
46 frases
Parts of a Microscope & How to Use a Microscope
Daily ConversationHigh School Students
B13
85 frases
Why Are Elements Arranged This Way? | LESSON 4-The Periodic Table | Science in English
Daily ConversationHigh School Students
B137
19 frases
01 Music Basics - What is Music?
Daily ConversationHigh School Students
B212
98 frases
How To See Germs Spread Experiment (Coronavirus)
American AccentBusiness EnglishDaily ConversationHigh School Students
C13
131 frases
Unit Conversion & Significant Figures: Crash Course Chemistry #2
Daily ConversationHigh School StudentsUniversity Students
B12
21 frases
Unit 9.The blue sky
Daily ConversationHigh School StudentsUniversity Students
B194 frases
States of Matter | Solid Liquid Gas
Daily ConversationHigh School Students
B14
46 frases
Science in English #7 | Properties of Homogeneous Mixtures
Daily ConversationHigh School Students
Vocabulário e dicas de fala para esta lição
Esta aula de conversação usa o vídeo “Exploring the pH Scale”. As palavras que mais se repetem: ion, acid, solution, alkaline, hydrogen. Este vídeo tem 99 frases e 1062 palavras para praticar shadowing. A fala dura 7:43. O falante mantém um ritmo estável de cerca de 138 palavras por minuto, confortável para o shadowing. Apenas 64% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.
Vocabulário principal deste vídeo
15 palavras do vídeo que vale a pena aprender, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| acid substantivo | /ˈæsɪd/ | ácido |
| concentration substantivo | /ˌkɑn.sənˈtɹeɪ.ʃən/ | concentração |
| hydrogen substantivo | /ˈhaɪdɹəd͡ʒ(ə)n/ | hidrogênio, hidrogénio |
| ion substantivo | /ˈaɪ.ɑn/ | íon, ião |
| neutral adjetivo | /ˈnuː.tɹəl/ | neutro |
| juice substantivo | /d͡ʒuːs/ | sumo, suco |
| lemon substantivo | /ˈlɛmən/ | limão, limão siciliano |
| compare verbo | /kəmˈpɛɚ/ | comparar |
| stomach substantivo | /ˈstʌmək/ | estômago |
| depend verbo | /dɪˈpɛnd/ | depender |
| sodium substantivo | /ˈsəʊ.di.əm/ | sódio |
| household adjetivo | /ˈhaʊshoʊld/ | familiar |
| commonly advérbio | /ˈkɑmənli/ | comumente |
| substance substantivo | /ˈsʌbstəns/ | substância |
| indicator substantivo | /ˈɪn.dɪˌkeɪ.tə(ɹ)/ | indicador |
Pronúncia para ficar de olho
- Os sons de “sh” e “zh”: concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, shield /ˈʃild/, distinction /dɪˈstɪŋkʃən/, acidification /əˌsɪdɪfɪˈkeɪʃən/, magnesia /ˌmæɡˈniʒə/
- Palavras longas — acerte a sílaba tônica: concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, indicator /ˈɪn.dɪˌkeɪ.tə(ɹ)/, necessarily /ˌnɛs.əˈsɛɹ.ə.li/, electrical /ɪˈlɛktɹɪkəl/, numerical /n(j)uːˈmɛɹ.ɪ.kəl/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: acid /ˈæsɪd/, stomach /ˈstʌmək/, depend /dɪˈpɛnd/, household /ˈhaʊshoʊld/, contribute /kənˈtɹɪb.jut/
- /l/ final — a língua toca o céu da boca, não vira “u”: neutral /ˈnuː.tɹəl/, particle /ˈpɑɹtək(ə)l/, electrical /ɪˈlɛktɹɪkəl/, vertical /ˈvɝ.tɪ.kəl/, mineral /ˈmɪn.ə.ɹəl/
- /h/ — um sopro suave, diferente do “r”: hydrogen /ˈhaɪdɹəd͡ʒ(ə)n/, household /ˈhaʊshoʊld/, hydroxide /haɪˈdɹɒks.aɪd/, hydrochloric /ˌhaɪdrəʊˈklɔrɪk/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Faça shadowing frase por frase na velocidade normal, repetindo cada uma até o seu ritmo ficar igual ao do falante.
- Grave a sua voz e compare com o original, prestando atenção a palavras como acid, concentration, hydrogen.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.