Unit 2

Bahan Berasid, Beralkali dan Neutral di Sekeliling Kita

Di dapur, Nenek membuat jeruk mangga dengan cuka. Kemudian dia mencuci pinggan dengan sabun. Ayah pula menabur kapur di kebun sayur.
Bahan berasid, beralkali dan neutral ada di sekeliling kita. Mari kenal ciri dan kegunaannya!

酸性物质 = bahan berasid；碱性物质 = bahan beralkali；中性物质 = bahan neutral 这一课看看身边的酸性、碱性和中性物质：它们尝起来、摸起来有什么特点，平时有什么用途，还有什么天然的东西可以代替石蕊试纸。奶奶用醋腌芒果，用肥皂洗碗，爸爸在菜园撒石灰，这些都用到了酸碱知识。例子：腌芒果用的醋是酸性，洗碗的肥皂是碱性。注意：这一课最后还有复习，把整个单元的重点再整理一次。

acidic substance = bahan berasid; alkaline substance = bahan beralkali; neutral substance = bahan neutral This lesson looks at the acidic, alkaline and neutral things around us: how they taste and feel, how we use them, and which natural materials can replace litmus paper. Grandma pickles mango with vinegar and washes plates with soap, while Dad spreads lime in the vegetable garden. Example: the vinegar for the pickles is acidic, and the dishwashing soap is alkaline. Watch out: the lesson ends with a review of the whole unit, so keep the key ideas in mind.

Ciri bahan

Rasa dan sentuhan

Ciri ini membantu kita mengenal bahan

sifat	rasa	sentuhan	contoh
asid	masam	–	cuka, sos tomato, buah anggur
alkali	pahit	licin	air sabun, ubat gigi
neutral	tawar, manis atau masin	–	air suling, air gula, air garam

酸 = masam；苦 = pahit；滑 = licin；淡 = tawar；咸 = masin 酸性物质通常是酸味的，例如醋、番茄酱、葡萄。碱性物质通常带苦味，摸起来滑滑的，例如肥皂水、牙膏。中性物质的味道是淡的、甜的或咸的，例如蒸馏水、糖水、盐水。例子：洗手时肥皂摸起来滑溜溜，这就是碱性物质的特点。注意：盐水是咸的，但它是中性，不要以为咸就是酸性或碱性。

sour = masam; bitter = pahit; slippery = licin; tasteless = tawar; salty = masin Acidic substances usually taste sour, like vinegar, tomato sauce and grapes. Alkaline substances usually taste bitter and feel slippery, like soapy water and toothpaste. Neutral substances taste plain, sweet or salty, like distilled water, sugar water and salt water. Example: soap feels slippery on your hands when you wash them, which is a feature of an alkali. Watch out: salt water is salty but neutral, so a salty taste does not mean acid or alkali.

Cuba

Sabun terasa licin apabila disentuh. Sabun bersifat …

滑溜溜 = licin 摸起来滑滑的、尝起来苦苦的，通常是碱性物质的特点。肥皂、洗洁精、牙膏都是碱性。酸性的特点是酸味，中性的东西摸起来不会特别滑。例子：洗发水起泡后摸起来滑滑的，它也偏碱性。注意：这些特点只是“通常如此”，最准的方法还是用试纸检验。

slippery = licin Feeling slippery and tasting bitter are the usual features of an alkali. Soap, dishwashing liquid and toothpaste are all alkaline. An acid is known for its sour taste, and neutral things do not feel especially slippery. Example: shampoo feels slippery once it foams, and it leans alkaline as well. Watch out: these features are only usual signs; the most reliable way is still to test with indicator paper.

Penunjuk saintifik

Rasa dan sentuhan tidak selamat

Gunakan kertas litmus untuk keputusan yang tepat

Tidak selamat

bahan beracun tidak boleh dirasa; kulit boleh berasa perit

Tidak tepat

lidah setiap orang berbeza; rasa boleh mengelirukan

Cara saintifik

uji dengan kertas litmus dan rekod keputusan

科学指示剂 = penunjuk saintifik；有毒 = beracun；刺痛 = perit 用舌头尝、用手摸，都不是科学的检验方法。有些物质有毒，尝了会中毒；有些物质碰到皮肤会刺痛。而且每个人的感觉不一样，味道可能让人判断错。所以科学上用石蕊试纸来判断酸碱。例子：漂白水绝对不能尝也不能用手摸，要检验就用试纸。注意：老师说可以摸的安全物质才可以摸，而且摸完要马上洗手。

scientific indicator = penunjuk saintifik; poisonous = beracun; stinging = perit Tasting and touching are not scientific ways to test. Some substances are poisonous, and some make the skin sting. People also sense taste differently, so taste can mislead us. That is why scientists use litmus paper to decide whether something is an acid or an alkali. Example: bleach must never be tasted or touched; to test it, use indicator paper. Watch out: touch only the safe samples the teacher allows, and wash your hands right after.

Cuba

Mengapakah kita tidak boleh merasa bahan di makmal?

实验室安全 = keselamatan di makmal 实验室里的液体可能有毒或有腐蚀性，尝了会伤害身体，所以不可以尝。物质不一定是甜的，石蕊试纸会不会湿也跟能不能尝无关。例子：一瓶透明的液体看起来像水，其实可能是清洁剂。注意：看到不认识的液体，不闻、不尝、不摸，先问老师。

lab safety = keselamatan di makmal Liquids in a lab may be poisonous or harmful, so tasting them can hurt the body. A substance is not necessarily sweet, and whether litmus paper gets wet has nothing to do with tasting. Example: a bottle of clear liquid may look like water but actually be a cleaning agent. Watch out: with any unknown liquid, do not sniff, taste or touch it; ask the teacher first.

Kegunaan

Bahan berasid dan beralkali dalam kehidupan

Dalam pertanian, perubatan dan rumah

Pertanian

kapur (alkali) ditabur pada tanah berasid

Perubatan

ubat gastrik (alkali) mengurangkan asid dalam perut

Isi rumah

cuka, asam jawa (asid) untuk masakan dan membersih; sabun (alkali) untuk mencuci

农业 = pertanian；医药 = perubatan；家用产品 = produk kegunaan isi rumah；石灰 = kapur；罗望子 = asam jawa 酸碱物质在生活中很有用。农民在酸性的土地上撒碱性的石灰，让土地适合种菜。胃药是碱性的，可以减少胃里过多的酸。家里用酸性的醋和罗望子煮菜、清洁，用碱性的肥皂洗东西。例子：奶奶用罗望子水擦铜锅，铜锅就变得亮亮的。注意：石灰是碱性，醋和罗望子是酸性，别把它们的性质记反了。

agriculture = pertanian; medicine = perubatan; household products = produk kegunaan isi rumah; lime = kapur; tamarind = asam jawa Acids and alkalis are very useful. Farmers spread alkaline lime on acidic soil so vegetables grow well. Gastric medicine is alkaline and reduces extra acid in the stomach. At home, acidic vinegar and tamarind are used for cooking and cleaning, and alkaline soap is used for washing. Example: Grandma rubs tamarind water on a brass pot and it starts to shine. Watch out: lime is alkaline while vinegar and tamarind are acidic, so do not swap them around.

Cuba

Tanah kebun Pak Hassan terlalu berasid. Dia menabur kapur. Kapur bersifat …

用石灰改良土地 = menabur kapur 土地太酸，蔬菜长不好。要减少酸，就要加相反性质的东西，也就是碱性的石灰。如果再加酸性的东西，土地会更酸；中性的东西则帮不上忙。例子：果园的土地太酸时，园主也会撒石灰。注意：酸和碱相遇，会互相抵消一部分，这叫中和。

spreading lime = menabur kapur When soil is too acidic, vegetables grow poorly. To reduce the acid, we add something of the opposite kind, which is alkaline lime. Adding an acid would make the soil even more acidic, and a neutral substance would not help. Example: an orchard owner also spreads lime when the soil becomes too acidic. Watch out: when an acid meets an alkali they cancel each other out partly, and this is called neutralising.

Ubat gigi

Mengapa kita memberus gigi?

Asid dalam mulut boleh merosakkan gigi

Ubat gigi (alkali) meneutralkan asid dalam mulut.

中和 = meneutralkan；糖果 = gula-gula；刷牙 = memberus gigi 吃完糖果，牙缝里的食物残渣会被细菌变成酸，酸会慢慢伤害牙齿。牙膏是碱性的，刷牙时它会把口中的酸中和掉，牙齿就比较安全。动画就是这个过程。例子：Kumar 每晚吃完宵夜都刷牙，所以很少蛀牙。注意：牙膏是碱性，不是酸性；如果牙膏是酸的，反而会伤害牙齿。

neutralise = meneutralkan; sweets = gula-gula; brush teeth = memberus gigi After we eat sweets, bits of food on the teeth are turned into acid, and this acid slowly damages the teeth. Toothpaste is alkaline, so brushing neutralises the acid in the mouth and keeps the teeth safer. The animation shows this process step by step. Example: Kumar brushes his teeth every night after supper, so he seldom gets cavities. Watch out: toothpaste is alkaline, not acidic; an acidic paste would harm teeth instead.

Fikir

Selepas makan gula-gula, Kumar memberus gigi. Mengapakah ini baik?

推理题 = soalan berfikir 吃糖后口中变酸。牙膏是碱性的，刷牙时碱把酸中和，所以对牙齿好。牙膏不会增加口中的酸，也不会让嘴巴变酸。例子：有些漱口水也是用来减少口中的酸。注意：回答“为什么”时，要同时说出牙膏的性质（碱性）和它做了什么（中和酸）。

thinking question = soalan berfikir After sweets, the mouth becomes acidic. Toothpaste is alkaline, and when we brush, the alkali neutralises the acid, which is good for the teeth. Toothpaste does not add acid or make the mouth sour. Example: some mouthwashes are also meant to reduce acid in the mouth. Watch out: a good answer to why gives both the property of toothpaste, alkaline, and what it does, neutralising acid.

Padankan

Bahan dan kegunaannya

用途配对 = padankan kegunaan 石灰撒在酸性的土地上；醋用来腌芒果；胃药减少胃里过多的酸；肥皂用来洗碗。每样东西都跟它的性质有关：石灰、胃药、肥皂是碱性，醋是酸性。例子：除了芒果，醋也可以腌洋葱和黄瓜。注意：胃药是吃进肚子里的，石灰不可以吃，它们虽然都是碱性，用途完全不同。

matching uses = padankan kegunaan Lime is spread on acidic soil; vinegar preserves pickled mango; gastric medicine reduces extra stomach acid; soap washes the plates. Each use is linked to the property: lime, gastric medicine and soap are alkaline, while vinegar is acidic. Example: besides mango, vinegar can also pickle onions and cucumbers. Watch out: gastric medicine is swallowed but lime must never be eaten; both are alkaline yet their uses are completely different.

Pengganti kertas litmus

Penunjuk daripada tumbuhan

Ekstrak tumbuhan juga berubah warna

penunjuk	dalam asid (limau nipis)	dalam alkali (soda bikarbonat)
ekstrak kubis ungu	merah jambu	hijau
ekstrak bunga raya	merah jambu	hijau
ekstrak kunyit	kuning	merah

Penunjuk lain: kertas pH

提取液 = ekstrak；紫甘蓝 = kubis ungu；大红花 = bunga raya；黄姜 = kunyit；pH 试纸 = kertas pH 没有石蕊试纸时，可以用植物的汁当指示剂。紫甘蓝汁在酸里变粉红色、在碱里变绿色；大红花汁也是酸里粉红、碱里绿色；黄姜汁在酸里还是黄色，在碱里却变红。pH 试纸也是一种指示剂。例子：把青柠汁滴进紫甘蓝汁，紫色马上变成粉红色。注意：黄姜汁在酸里不变色，要用碱才看得出变化。

extract = ekstrak; purple cabbage = kubis ungu; hibiscus = bunga raya; turmeric = kunyit; pH paper = kertas pH Without litmus paper, plant juices can act as indicators. Purple cabbage extract turns pink in an acid and green in an alkali; hibiscus extract also turns pink in an acid and green in an alkali; turmeric extract stays yellow in an acid but turns red in an alkali. pH paper is another indicator. Example: drip lime juice into purple cabbage extract and the purple turns pink at once. Watch out: turmeric does not change in an acid, so only an alkali shows its colour change.

Cuba

Ekstrak kubis ungu dititiskan ke dalam cuka. Warnanya menjadi …

紫甘蓝指示剂 = penunjuk kubis ungu 醋是酸性的。紫甘蓝汁遇到酸会变成粉红色；遇到碱才会变绿色。蓝色不是它在酸里的颜色。例子：紫甘蓝汁滴进橙汁，同样会变粉红色。注意：先判断液体是酸还是碱，再看表格里的颜色。

purple cabbage indicator = penunjuk kubis ungu Vinegar is acidic. Purple cabbage extract turns pink when it meets an acid and turns green only with an alkali. Blue is not its colour in an acid. Example: a few drops of the extract in orange juice also turn pink. Watch out: first decide whether the liquid is an acid or an alkali, then read the colour from the table.

Ingat semula

Pokok asid, alkali dan neutral

Rumusan unit

ASID

litmus biru → merah
rasa masam
cuka, jus oren, sos tomato

ALKALI

litmus merah → biru
pahit, licin
sabun, ubat gigi, air kapur sirih

NEUTRAL

tiada perubahan
tawar, manis, masin
air suling, air gula, air garam

Bina “pokok” dengan tiga dahan: setiap dahan untuk satu sifat.

复习 = ingat semula；树枝 = dahan 整个单元的重点：酸性让蓝纸变红，味道酸；碱性让红纸变蓝，苦而滑；中性两张纸都不变，味道淡、甜或咸。可以画一棵“酸碱中性树”，三根树枝各挂一类例子，复习更容易。例子：在“碱性”树枝上挂肥皂、牙膏和石灰水的卡片。注意：同一种东西只能挂在一根树枝上，挂之前先想清楚它的性质。

review = ingat semula; branch = dahan The key points of the unit: an acid turns blue litmus red and tastes sour; an alkali turns red litmus blue and is bitter and slippery; a neutral substance changes neither strip and tastes plain, sweet or salty. Drawing a tree with three branches, one per property, makes revision easier. Example: hang cards for soap, toothpaste and lime water on the alkali branch. Watch out: each item belongs on only one branch, so decide its property before you hang it.

Mari jawab

Cecair X tidak mengubah warna kertas litmus merah dan biru. Cecair X mungkin …

找出中性液体 = cari cecair neutral 两张试纸都没变色，表示液体是中性。盐水是中性；醋是酸性，会让蓝纸变红；肥皂水是碱性，会让红纸变蓝。例子：蒸馏水和糖水也都可以是这题的答案。注意：盐水是咸的，但咸味不会让试纸变色。

finding the neutral liquid = cari cecair neutral If neither strip changes, the liquid is neutral. Salt water is neutral; vinegar is acidic and would turn blue litmus red; soapy water is alkaline and would turn red litmus blue. Example: distilled water and sugar water would also fit this question. Watch out: salt water tastes salty, but saltiness does not change the colour of litmus.

Mari jawab

Siti berkata, “Kopi ini pahit, jadi kopi pasti alkali.” Adakah cara Siti betul?

高阶思维 = KBAT Siti 只靠苦味就说咖啡一定是碱性，这样不科学。味道只是线索，不能当作证据；要知道咖啡的性质，必须用石蕊试纸来检验。例子：苦瓜汁也很苦，但要知道它是酸是碱，同样要用试纸检验。注意：答“对”的两个理由都错了，舌头不会比石蕊试纸更准。

higher-order thinking = KBAT Siti decides coffee must be alkaline just because it is bitter, which is not scientific. Taste is only a clue, not proof; to know the property of coffee, it must be tested with litmus paper. Example: bitter gourd juice is bitter too, but its property still has to be found with indicator paper. Watch out: both reasons for answering yes are wrong; the tongue is never more accurate than litmus paper.

Ringkasan

Syabas!

kenal · guna · uji

Asid masam, alkali pahit dan licin, neutral tawar. Rasa bukan penunjuk saintifik. Kapur, ubat gastrik, cuka dan ubat gigi berguna dalam kehidupan.

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