Реши задание на изображении

Quick answers

Task 1: 1 → B, 2 → C, 3 → A

Task 2:

1. Oxygen gas (\(\mathrm{O_2}\)) — Element
2. Pure water (\(\mathrm{H_2O}\)) — Compound
3. Sea water — Mixture
4. Iron filings (\(\mathrm{Fe}\)) — Element
5. Carbon dioxide (\(\mathrm{CO_2}\)) — Compound
6. Air — Mixture

Task 3:

1. \(\mathrm{NaCl}\): 2 elements — sodium (Na), chlorine (Cl)
2. \(\mathrm{H_2SO_4}\): 3 elements — hydrogen (H), sulfur (S), oxygen (O)
3. \(\mathrm{CaCO_3}\): 3 elements — calcium (Ca), carbon (C), oxygen (O)

Task 4 (visible part):

1. Sand from water — Filtration

Why / key steps

• Element: only one type of atom. \(\mathrm{O_2}\) has two atoms, but both are oxygen, so it is still an element.
• Compound: different elements chemically bonded in a fixed ratio, e.g. \(\mathrm{H_2O}\) or \(\mathrm{CO_2}\).
• Mixture: substances together but not chemically bonded; can be separated by physical methods. Sea water and air are mixtures.
• Counting elements in a formula: count different chemical symbols, not subscripts. In \(\mathrm{H_2SO_4}\), the symbols are H, S, O → 3 elements. In \(\mathrm{CaCO_3}\), Ca, C, O → 3 elements.
• Separation: choose a method based on a physical property. Insoluble solid in liquid → filtration.

Check

• Task 1: B matches “identical atoms of a single type,” C matches “different atoms strongly bonded,” A matches “mixed but not bonded.”
• Task 2: \(\mathrm{O_2}\) and Fe are elements; \(\mathrm{H_2O}\) and \(\mathrm{CO_2}\) are compounds; sea water and air are mixtures.
• Task 3: subscripts tell atom count, not element count.
• Task 4: sand is insoluble, so it can be filtered out.

Task 4 is cut off after item 1. Are there more items below it?