Is Matter Around us Pure? — Practice Quiz

Suspension

Step 1: Suspensions have large particles that are visible to naked eye. Step 2: These large particles are heavy and affected by gravity. Step 3: When left undisturbed, gravity pulls these particles down, causing them to settle. Step 4: Solutions have dissolved particles that are too small to settle. Step 5: Colloids have particles that are small enough to remain suspended due to constant motion.

20%

Step 1: Calculate total mass of solution = mass of solute + mass of solvent = 25g + 100g = 125g. Step 2: Use the formula: Mass percentage = (Mass of solute/Mass of solution) × 100. Step 3: Mass percentage = (25g/125g) × 100. Step 4: Mass percentage = 0.2 × 100 = 20%. Step 5: The answer is 20%, meaning 20g of salt is present in every 100g of solution.

Water

Step 1: A compound is made of two or more elements chemically combined in fixed proportion. Step 2: Water (H2O) contains hydrogen and oxygen elements chemically bonded together. Step 3: Iron, oxygen, and gold are pure elements - they contain only one type of atom. Step 4: Elements cannot be broken down into simpler substances by chemical means. Step 5: Compounds can be broken down into their constituent elements through chemical reactions.

Chemical change

Step 1: When iron and sulphur are heated together, they react chemically to form iron sulphide. Step 2: The new compound (iron sulphide) has completely different properties from iron and sulphur. Step 3: Chemical bonds form between iron and sulphur atoms, creating a new substance. Step 4: This cannot be reversed by simple physical means - you cannot separate iron and sulphur easily from iron sulphide. Step 5: Chemical changes involve formation of new substances with different properties.