"General Review of the Ninth Grade Chemistry Volume 1" PPT courseware 3

"General Review of the Ninth Grade Chemistry Volume 1" PPT courseware 3

Unit 1 Entering the World of Chemistry

Topic 1 Chemistry makes the world more colorful

1. What is chemistry

Chemistry is a science that studies the composition, structure, properties and changes of substances.

Composition, structure: elements make up matter, molecules and atoms make up matter

1. Distinguish between "change" and "nature"

When describing "nature", there are usually words such as "have, can, can, and will", which are descriptions of results.

2. Distinguish between “physics” and “chemistry”

"Physical" in "property" is generally a visible state

The key to "change" is "whether new substances are produced or not"

Topic 3 Entering the chemistry laboratory

1. Laboratory rules

1. The "three no's" principle: don't touch, don't smell, don't taste

2. The "minimum amount" principle: 1~2mL of liquid, and the solid should cover the bottom of the test tube.

3. Drug handling: put into designated containers

2. Experimental equipment and operation

1. Selection of laboratory gas preparation equipment

(1) Generating device: state and conditions of reactants

Solid-solid heating, solid-liquid heating, solid-liquid non-heating

(2) Collection device: properties of products

How does the density compare to air (air discharge method upward or downward); not easily soluble in water and does not react with water (drainage method)

Unit 2 The air around us

1. What is air made of?

1. Experimental determination

(1) Selection of combustion substances: the product is solid or liquid

(2) Requirements for the device: good air tightness

2. Conclusion: Air is composed of a variety of gases, N2 accounts for 78%, O2 accounts for 21%, rare gases 0.94%, CO2 0.03%, and others 0.03% (volume ratio)

2. Air is a precious resource (purpose)

1.O2: supports combustion and supplies breathing

2. N2: An important raw material for manufacturing nitric acid and nitrogen fertilizer; because of its inactive chemical properties, it is often used as a protective gas; the low temperature of liquid nitrogen is used as a freezing anesthetic for surgery, or a refrigerant for superconducting materials.

3. Rare gas: It is extremely inactive in chemical properties, so it can also be used as a protective gas, welding metal, filling light bulbs, and can be used as an electric light source when energized.

Units 4 and 5 Material composition and law of conservation of mass

1. Several microscopic particles that constitute matter

The particles that make up matter?

Molecule A particle that maintains the chemical properties of a substance.

atom The smallest particle involved in chemical changes.

Ion A charged atom or group of atoms.

Characteristics of molecules

Molecules are in constant motion.

There are gaps between molecules.

The size and mass of molecules are small.

Give examples of the characteristics of molecules.

6. Law of Conservation of Mass and Chemical Equations

1. Law of conservation of mass?

The sum of the masses of the substances participating in the reaction is equal to the sum of the masses of the substances produced after the reaction. This law is called the law of conservation of mass.

Note: (1) "participate" and "generate" in the concepts;

(2) The law of conservation of mass can only be applied to chemical changes, not physical changes.

Why does the law of conservation of mass exist in nature?

In a chemical reaction, the types of atoms do not change before and after the reaction, the number does not increase or decrease, and the mass of the atoms does not change.

Exercise: When a substance is burned in oxygen, only CO2 is generated, then the composition of the substance must contain ( ) elements, and may contain ( ).

chemical equation

1. Concept: Use chemical formulas to express chemical reactions.

2. Principles for writing chemical equations:

a. Based on objective facts;

b.Satisfy the law of conservation of mass.

3. Note: "△", "ignition" and "high temperature" in the conditions of chemical equations have different meanings and must not be mixed.

4. Be able to read chemical equations.

practise

Use a chemical equation to express the process of removing small amounts of impurities from the following substances (impurities are in parentheses).

(1) CO (CO2) (2) CO2 (CO)

(1) CO2 can be removed by passing the mixed gas through a sufficient amount of NaOH solution. NaOH solution does not react with CO.

CO2+2NaOH==Na2CO3+H2O

(2) Pass the mixed gas through a glass tube containing a sufficient amount of hot copper oxide. After sufficient reaction, the CO turns into CO2 and is exported. CO2 does not react with copper oxide.

CO+CuO===Cu+CO2

Discussion: How many methods can you use to distinguish between CO2 and CO?

Reference answers: (1) It is possible to use different densities;

(2) Carbon dioxide can make clear lime water turbid;

(3) Carbon dioxide can turn purple litmus test solution red;

(4) Carbon dioxide can extinguish fires, but carbon monoxide can burn;

(5) Carbon monoxide can turn dark red blood into bright red.

Unit 7: Fuel and its Utilization

1. Burning and extinguishing fire

Burning conditions:

(1) Combustibles; (2) Oxygen (or air);

(3) Reach the minimum temperature required for combustion (also called ignition point)

Fire extinguishing principle:

(1) Remove combustible materials or isolate combustible materials from other items (to remove fuel from the bottom of the cauldron);

(2) Isolate oxygen (or air);

(3) Reduce the temperature below the ignition point of combustibles.

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