1. Normally, it is a colorless and odorless gas with a density greater than that of air. 2. Comparison of gas density: Comparative formula 3. The average formula of air: 29; the formula of oxygen: 32 (density is greater than air)

(1) Sulfur combustion: Sulfur Oxygen—ignite—sulfur dioxide S O2—ignite—SO2 Phenomenon: In the air: a weak light blue flame is emitted, heat is released, and a gas with a pungent odor is generated. In oxygen: emits a bright blue-purple flame, releases heat, and generates a gas with a pungent odor. (2) Charcoal burning Carbon Oxygen—ignite—carbon dioxide C O2—ignite—CO2 Phenomenon: In the air: red light, heat, and gas that can turn clear lime water into turbidity In oxygen: emits white light, releases heat, and generates gases that can make clear lime water turbid. (3) Combustion of iron in oxygen Iron Oxygen—ignite—iron oxide F e O2—ignite—F e3O4 Phenomenon: Combustion in oxygen: violent combustion, sparks radiating, heat release, and formation of a black solid

1) Combination reaction: the reaction of two or more substances to produce another substance (characteristic: multiple changes) 2) Oxidation reaction: the reaction between a substance and oxygen (oxygen element - oxygen, oxide, etc.)

Potassium chlorate to produce oxygen Manganese dioxide MnO2 (1) Potassium chlorate - heating - potassium chloride oxygen KCIO3 - △ - KCl O2 (2) Device: Solid heating type (3) Methods of collecting oxygen (depending on the density and solubility of the gas): upward air discharge and drainage method (4) Fullness check: upward air exhaust method: place the wooden stick with sparks on the mouth of the bottle. If it re-ignites, it will be full; drainage method: there are bubbles emerging from the mouth of the bottle. (5) Check whether it is oxygen: put the wooden stick with sparks into the bottle, and if it re-ignites, it will be oxygen. (6) Operation sequence: Check and collect at fixed points (tea house collects interest at fixed points)

hydrogen peroxide to oxygen (1) Hydrogen peroxide-manganese dioxide-water oxygen H2O2—MnO2—H2O O2 (2) Device: solid-liquid non-heating type (3) The functions of the long-neck funnel and the separatory funnel: add liquid at any time; the long-neck funnel: the lower end nozzle extends below the liquid level (liquid seal) - to prevent gas from escaping from the long-neck funnel; the advantages of the separatory funnel: can Control the flow rate of liquid to obtain smooth air flow (4) Operation sequence: connect the instrument, check the air tightness of the device, load the medicine (put the solid first and then add the liquid), collect the gas

catalyst 1) Catalyst: A substance that can speed up the chemical reaction rate of other substances in a chemical reaction without changing its own quality and chemical properties before and after the reaction. 2) Verify that manganese dioxide is a catalyst for the hydrogen peroxide to oxygen reaction: 1. Prove that manganese dioxide can speed up the reaction rate - Comparative experiment 2. Prove that the mass of manganese dioxide remains unchanged before and after the reaction - Separate from the mixture (filtration, washing , dried) and weighed after coming out 3. Prove that the chemical properties of manganese dioxide remain unchanged before and after the reaction - do a comparative experiment again 3) Verify that manganese dioxide is a catalyst for the decomposition reaction of potassium chlorate: 1. Prove that it can accelerate the reaction rate 2. Prove that the chemical properties of manganese dioxide do not change before and after the reaction 3. Prove that the quality of manganese oxide before and after the reaction does not change (manganese dioxide is removed from the mixture separation)

How to separate manganese dioxide from the reaction mixture: 1. Dissolve, filter, wash, dry—obtain manganese dioxide 2. Dissolve, filter, evaporate—obtain potassium chloride

The basis for selecting the generating device (solid-solid heating type, solid-liquid non-heating type): the state of the reactants and reaction conditions The basis for selecting the collection device (upward air exhaust method, downward air exhaust method, drainage method): density and dissolution of gas

decomposition reaction Decomposition reaction: a reaction in which one reactant produces two or more other substances Multifunctional bottle: 1. Collect gas: Upward air exhaust method: long tube in air, short tube out air; downward air exhaust method: short tube in air, long tube out air; Drainage method: short tube in air, long tube out Out of water 2. Test gas (long tube inlet, short tube out) Example: Test whether oxygen contains carbon dioxide - clarify lime water