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Revision videos, vocabulary practice and written questions for IGCSE.

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IGCSE Computer Science

Revision videos for IGCSE Computer Science, unit by unit.

IGCSE Co-ordinated Sciences

Biology revision for Cambridge IGCSE Co-ordinated Sciences, topic by topic. Vocabulary videos with Vietnamese meanings, then the concepts, then a quiz.

IGCSE Computer Science

30 videos

Revision videos for IGCSE Computer Science, unit by unit: Grade 9 data representation, data transmission and hardware.

Grade 9 · Unit 1: Data representation

Denary, binary and hexadecimal

Place values, converting denary to binary and back, and why hex is used for bytes.

binaryhexadecimaldenary

Binary addition, overflow and shifts

Adding binary numbers with carries, overflow when a ninth bit is needed, and logical shifts as multiply and divide.

binary additionoverflowlogical shift

Two's complement

Negative numbers in binary: the -128 place value, invert and add one, and reading a signed byte.

two's complementnegative numbers

Text: ASCII and Unicode

Character sets give every character a code. ASCII's 128 codes, Unicode's millions, and the storage trade-off.

ASCIIUnicodecharacter set

Images

Pixels, resolution, colour depth, image file size and metadata.

pixelsresolutioncolour depth

Sound

Sampling an analogue wave: sample rate, bit depth, quality against file size.

samplingsample ratebit depth

Storage units and file sizes

Bit to pebibyte in steps of 1024, and calculating image and sound file sizes.

KiBMiBfile size

Compression

Why files are compressed, lossy against lossless, and run-length encoding step by step.

lossylosslessRLE

Unit 1 quiz

Ten questions with a think-time countdown and explained answers.

Grade 9 · Unit 2: Data transmission

Data packets and packet switching

Packet structure, routing, out-of-order arrival and reassembly.

Simplex, half-duplex and full-duplex

Which way the data flows, and when.

transmission mode

Serial and parallel transmission

Bits one by one or all at once, skew, crosstalk and USB.

serialparallelUSB

Error detection

Why errors happen, and checksums, echo checks and ARQ.

Parity checks

Parity bits and parity blocks, including finding and fixing a flipped bit.

Check digits

The multiply, add, divide-by-10 method with a worked example and a practice question.

check digitworked example

Encryption

Eavesdroppers, symmetric keys and the public and private key pair.

Unit 2 quiz

Ten questions with a think-time countdown and explained answers.

Crosstalk in transmission

How a signal leaks into a neighbouring wire, corrupts data, and how twisted pairs and shielding fix it.

crosstalkinterferencetwisted pair

When to use serial or parallel

Choosing between serial and parallel: inside a computer, computer to printer, USB, Ethernet and a distance rule of thumb.

serialparallelprinterUSB

Grade 9 · Unit 3: Hardware

Inside the CPU

The control unit, ALU and registers, the Von Neumann architecture and the three buses.

The fetch-decode-execute cycle

Follow one instruction through the PC, MAR, MDR, CIR and ACC registers, then run a small program.

cpuregistershardware

What makes a CPU faster?

Clock speed, number of cores and cache size, with the run times worked out.

cpuperformancehardware

Embedded systems

A computer built into a device for one job: examples, and how it differs from a general-purpose computer.

embeddedhardware

Input devices

Keyboards, mice, touch screens, microphones, cameras, scanners and barcode / QR readers.

Output devices

Screens, projectors, printers, 3D printers and speakers: what each one does.

Sensors and actuators

A control loop: a sensor measures, the processor decides, an actuator acts. A thermostat shown step by step.

sensorsactuatorshardware

Primary storage: RAM, ROM and virtual memory

Volatile RAM, non-volatile ROM with the boot program, and what virtual memory does when RAM is full.

ramrommemoryhardware

Secondary storage

Magnetic, optical and solid-state storage, plus cloud storage.

storagehardware

Network hardware: NIC, MAC, IP and routers

What a network interface card, MAC address, IP address (IPv4 and IPv6) and router each do.

networkipmacrouterhardware

Unit 3 quiz

Ten questions with a think-time countdown and explained answers.

IGCSE Co-ordinated Sciences

13 videos

Cambridge IGCSE Co-ordinated Sciences biology, topic by topic: vocabulary with Vietnamese meanings, the concepts, then a quiz. Slow, simple English for students who learn in a second language.

B4 Enzymes

B4 Enzymes: key vocabulary

Twelve key words for IGCSE Co-ordinated Sciences topic B4, with the Vietnamese meaning, how to say each word, a picture and an example. Ends with a test section, and a typing trainer on the site.

vocabularyenzymesVietnamese

What are enzymes?

Why the body needs catalysts, what a catalyst does, and why enzymes are proteins that work as biological catalysts. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

enzymescatalystVietnamese

How enzymes work

The active site, the substrate, the enzyme-substrate complex and the products; why complementary shapes make an enzyme specific. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

enzymesactive siteVietnamese

Enzymes: temperature and pH

Why a higher temperature speeds up an enzyme, what the optimum is, and how heat or the wrong pH changes the shape of the active site (denaturation). With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

enzymestemperaturepHdenaturationVietnamese

Investigating enzymes: temperature and pH

A practical with amylase, starch and iodine on a spotting tile: how to test the effect of temperature and pH, keep it a fair test and read the results. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

enzymespracticaliodineamylaseVietnamese

B4 quiz: enzymes

Ten think-time questions on enzymes: catalysts, the active site, specificity, temperature, pH and the amylase practical. Below the video: written workbook questions with model answers.

quizenzymesrevision

B5 Plant nutrition

B5 Plant nutrition: key vocabulary

Twelve key words for IGCSE Co-ordinated Sciences topic B5, with the Vietnamese meaning, how to say each word, a picture and an example. Ends with a test section, and a typing trainer on the site.

vocabularyphotosynthesisVietnamese

Photosynthesis explained

What photosynthesis is, the word and balanced equations, how chlorophyll changes light energy into chemical energy, and what plants do with the glucose. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

photosynthesischlorophyllequationVietnamese

Inside a leaf: structure and function

A cross-section of a dicotyledonous leaf: cuticle, epidermis, palisade and spongy mesophyll, vascular bundle with xylem and phloem, stomata and guard cells, and what each one does. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

leafstomatapalisadexylemVietnamese

Does a plant need chlorophyll, light and CO₂?

How to test a leaf for starch, and the experiments that show chlorophyll, light and carbon dioxide are needed for photosynthesis, with controls. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

photosynthesispracticalstarch testcontrolsVietnamese

The rate of photosynthesis

A pondweed experiment: counting oxygen bubbles to see how light intensity and temperature change the rate of photosynthesis, and what a limiting factor is. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

photosynthesisratelimiting factorpracticalVietnamese

Nitrate and magnesium: what plants need

Why plants need nitrate ions (for amino acids and proteins) and magnesium ions (for chlorophyll), and what deficiency does to growth. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.

nitratemagnesiumdeficiencymineralsVietnamese

B5 quiz: plant nutrition

Ten think-time questions on plant nutrition: photosynthesis, chlorophyll, leaf structure, transport, the starch test, limiting factors and mineral ions. Below the video: written workbook questions with model answers.

quizplant nutritionrevision

Practise what you learned

Type the words, answer the questions and check yourself after each video.

B4 Enzymes: workbook questions – Eight written questions with model answers: write your answer, check it, and tick the marks you earned. Vietnamese help for every question.
B5 Plant nutrition: workbook questions – Nine written questions with model answers: write your answer, check it, and tick the marks you earned. Vietnamese help for every question.
B4 Enzymes: vocabulary trainer – Learn the 12 words by typing them: from the Vietnamese meaning, from the definition, from the sound and from an example sentence. Words you miss come back; words you know come back later.
B5 Plant nutrition: vocabulary trainer – Learn the 12 words by typing them: from the Vietnamese meaning, from the definition, from the sound and from an example sentence. Words you miss come back; words you know come back later.
Check yourself: What are enzymes? – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: How enzymes work – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: Enzymes: temperature and pH – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: Investigating enzymes: temperature and pH – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: Photosynthesis explained – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: Inside a leaf: structure and function – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: Does a plant need chlorophyll, light and CO₂? – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: The rate of photosynthesis – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Check yourself: Nitrate and magnesium: what plants need – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.

See all practice →