E ExamMaster

CBSE Class 8 · Science

Nature of Matter: Elements, Compounds, and Mixtures

Official NCERT chapter from Curiosity (book code hecu1). ExamMaster notes are original teaching at CBSE Class 8 depth.

This lesson follows the official chapter “Nature of Matter: Elements, Compounds, and Mixtures” in Curiosity. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 8
  • Easy level
  • 8 concepts

1What Are Mixtures?

A mixture has more than one substance sitting together, and you can often unmix them by a physical job (pick, sieve, evaporate) as taught. Air, salt-and-sand, a salad — the parts keep their own tests.

A new substance with a new test is not this mixture-word.

Figure. A mixture is more than one substance sharing a jar and keeping their own properties. Iron and sulphur mixed can still be split by a magnet. The mix is a place, not a new substance.

How it works

  1. Name two parts you can still test separatelyThis mix.
  2. Name an unmix-job if you have oneSieve, magnet, evaporate.
  3. Call it a mixtureParts kept their tests.

2What Are Pure Substances?

A pure substance here is one kind of stuff with one set of tests (a melting story as taught, a single substance-word). Pure is a test-word, not “clean-looking”. A clear mix can still be a mixture.

Filtered muddy water that still has dissolved salt is not pure water.

Figure. A pure substance is one kind of matter with one set of properties — one melting point, one boiling point. A mixture fails that test because each part still has its own numbers.

How it works

  1. Ask whether more than one substance-word remainsThe test.
  2. If only one, call it pure in this chapter’s senseOne stuff.
  3. Refuse “looks clean” as the only testClear ≠ pure.

3What Are the Types of Pure Substances?

Pure substances split into elements and compounds as taught. An element is a stuff not broken into simpler stuffs by the class’s chemical jobs. A compound is more than one element joined as a new stuff with new tests (water, not a mix of gases you can sieve).

A mixture of iron and sulphur is not the compound you get after a taught heat-join.

Figure. Every pure substance is an element or a compound. An element is one type of atom. A compound is two or more types locked in a fixed ratio, with new properties of its own.

How it works

  1. Element: one stuff, not unmade by class chemistryThe first type.
  2. Compound: a new stuff from a join, new testsThe second type.
  3. Keep mixture as the unjoined sitting-togetherThree drawers.

4What Are Minerals?

A mineral at this class is a named natural stuff (often a compound or an element in the ground) you take for a use — as the lesson listed. It is not every pretty rock, and not a vitamin-ad “mineral”.

A garden pebble with no taught name is not this mineral-list.

Figure. A mineral is a named natural substance with a fixed composition — diamond is carbon, haematite is Fe₂O₃, rock salt is NaCl. A rock can hold more than one mineral; the mineral is the pure name you can write.

How it works

  1. Name a taught mineral or ore-word if you were given oneThis one.
  2. Name a use or a taking-cost if taughtThe job.
  3. Keep it in the pure-or-rock drawer the lesson usedNot a snack-ad.

5A definition is a test you can run

Mixture versus pure is a test: can you unmix by a physical job, and do parts keep their tests? If you cannot run that question, you have a heading.

A slogan “chemical-free” is not the test.

Figure. A definition here is a test, not a school name. If a physical test splits the sample, it is a mixture. If not, ask whether new properties sit in a fixed ratio: yes is a compound, no is an element.

How it works

  1. Try an unmix-job or a parts-testThe object.
  2. See parts remain or a new stuff appearMixture, or compound.
  3. Then the words have contentThe definition ran.

6Name the given before the unknown

The given is the sample and the job (unmix or heat-join). The unknown is mixture / element / compound. Copy the tests of the parts before you say compound.

Calling saltwater an element because it is clear is a silent given.

Figure. Before you classify, name what you were given and the test you will run. Salt plus sand is the given; water and a filter is the test; sand left and salt water are what the test names. The unknown is not a guess at the start.

How it works

  1. Name the sample and what you didThe given.
  2. Name the drawerThe unknown.
  3. Use parts-tests or new-testsGiven first.

7One worked case is enough at this class

One unmix or one join-contrast is enough. A page of the same salt-sand clone does not add a new drawer.

Ten twins of one sieve are still one idea.

Figure. One worked pair is enough at this class: iron with sulphur. Mixed, a magnet still takes the iron — mixture. Heated, the magnet fails because FeS is a new substance — compound. Do not invent a second pair until this one is solid.

How it works

  1. Run one sortThe case.
  2. A second only as a checkOptional.
  3. StopThis class.

8A miss: swapping the school name for the picture

A jewellery-ad “pure gold” is a setting. The science is the test-word. A shiny photo and skipping unmix/join is the swap-miss.

A brand stamp is not an element-test.

Figure. The miss is treating the school name on the jar as the substance. If the magnet still takes iron, the sample is still a mixture, whatever the label says. The picture is the test, not the printed name.

How it works

  1. Keep the ad as a storyA setting.
  2. Ask mixture, element, or compoundThe science.
  3. Run a parts-test or a new-stuff testDo not swap.
Salt mixed with sand is
  1. A mixture — parts keep tests; you can unmix
  2. An element
  3. A compound called sand-salt

Sitting together, not a new stuff.

Notes

  • Mapped to the official NCERT chapter “Nature of Matter: Elements, Compounds, and Mixtures”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Recap

Hold these pegs from the official chapter “Nature of Matter: Elements, Compounds, and Mixtures”. The wording is ExamMaster’s teaching, not a textbook recap.

What Are Mixtures?
A mixture has more than one substance sitting together, and you can often unmix them by a physical job (pick, sieve, evaporate) as taught.
What Are Pure Substances?
A pure substance here is one kind of stuff with one set of tests (a melting story as taught, a single substance-word).
What Are the Types of Pure Substances?
Pure substances split into elements and compounds as taught.
What Are Minerals?
A mineral at this class is a named natural stuff (often a compound or an element in the ground) you take for a use — as the lesson listed.
A definition is a test you can run
Mixture versus pure is a test: can you unmix by a physical job, and do parts keep their tests? If you cannot run that question, you have a heading.
Name the given before the unknown
The given is the sample and the job (unmix or heat-join).

Practise Nature of Matter: Elements, Compounds, and Mixtures

Reading is free and needs no account. Practice, mocks and progress live in the app.

  • A 4-question practice set that ends the chapter
  • 1 quick check with worked explanations
  • Timed mocks scored with the real marking scheme
  • Readiness tracked per topic, kept on your device
Continue with Google — freeNo card, no trial. Works offline once installed.