Maharashtra State Board Class 7 Science Elements Compounds and Mixtures Notes / Textbook Exercises and Extra Question and Answers.
Class 7 Science Elements Compounds and Mixtures Notes
Matter:
- Matter refers to the substance an object is made of.
- It can exist in solid, liquid, or gaseous states.
- An object’s properties are determined by the matter it contains.
Properties of Matter:
- Matter has two essential properties: mass and volume.
- Mass and volume are attributed to the substances that matter comprises.
Substances:
- Substances are forms of matter made of a single constituent.
- Examples include gold, diamond, water, and chalk.
- These substances have consistent properties.
Mixtures:
- Mixtures are combinations of two or more substances.
- Proportions of components in mixtures can vary.
- No chemical change occurs during mixture formation.
Particles of Matter:
- All matter consists of tiny particles.
- The smallest particles are molecules.
- Elements are substances composed of identical atoms and cannot be further decomposed.
Elements:
- Elements are represented by symbols derived from their names.
- Some elements share initial letters, leading to the use of pairs of letters for symbols.
- Elements are classified into metals, non-metals, and metalloids based on their properties.
Compounds:
- Compounds are formed by the chemical combination of atoms from different elements.
- Compounds have properties distinct from their constituent elements.
- They are represented by molecular formulas.
Separating Mixtures:
Unwanted substances in mixtures can be separated using methods such as filtration, sorting, winnowing, and sublimation.
Separating Immiscible Liquids:
- Immiscible liquids in a mixture can separate into distinct layers.
- Heavier liquid settles at the bottom, while lighter liquid floats on top.
Difficult-to-Separate Mixtures:
Some mixtures, like turbid water, ink, and milk, contain tiny and light solid particles that remain evenly distributed and are hard to separate.
Chromatography:
- Chromatography is used to separate substances in a solution, especially when multiple substances are dissolved in small proportions.
- It is used in pharmaceutical science and scientific laboratories.
Who are my companions? [Solved]
| Group ‘A’ | Group ‘B’ |
| Stainless steel | (e) Alloy |
| Silver | (f) Metal |
| Bhajani mixture | (c) Mixture for milling |
| Salt | (b) Compound |
| Coal | (d) Element |
| Hydrogen | (a) Non-metal |
Write the names of elements from the following symbols : Zn, Cd, Xe, Br, Ti,Cu, Fe, Si, Ir, Pt.
- Zn – Zinc
- Cd – Cadmium
- Xe – Xenon
- Br – Bromine
- Ti – Titanium
- Cu – Copper
- Fe – Iron
- Si – Silicon
- Ir – Iridium
- Pt – Platinum
What are the molecular formulae of the following compounds?
Hydrochloric acid, sulphuric acid, sodium chloride, glucose, methane.
- Hydrochloric acid – HCl
- Sulfuric acid – H2SO4
- Sodium chloride – NaCl
- Glucose – C6H12O6
- Methane – CH4
