The first two units of chemistry in the ninth grade should be summarized in detail

Purity is relative, impure is absolute bumper boy. Ice water co-existence is pure, clean air must be a mixture, pure water is a mixture, and table salt is a mixture. Dry ice is not ice, and mercury is not silver.

Combustion and ** are both physical and chemical changes. Dry ice sublimation is a physical change, electrical and thermal conductivity is a physical change, rust and decay are chemical changes, and separating gases using different boiling points is a physical change.

1.The number of neutrons is not necessarily equal to the number of protons, the number of neutrons can be 0.

2.Relative atomic weight and molecular weight have no unit and are a ratio.

3.The empty mass of hydrogen is not 1, but slightly larger than 1.

4.Compounds composed of ions have no molecular weight, and some compounds such as silicon dioxide and silicon carbide have no molecular weight, and the significance of their chemical formula only explains the ratio of the number of atoms.

There is no O2 molecule in the noisy skin.

6.Food and beverage labels are marked with the amount of x (element symbol), which refers to an element and not an atom, let alone an element.

7.Most metal elements are solid at room temperature and pressure, but mercury is in a liquid state, and the melting point of cesium and gallium is close to room temperature and is easy to be in a supercooled state.

8.The amount of oxygen in the earth's crust is at the top of the list, but not in the air.

changes and properties of substances, determination of air composition and properties of oxygen, preparation methods; Uses, etc.

Chemical Equations and Phenomena Learn about basic chemical reactions.

This address is there, go find it,

The main content of the first unit of the People's Education Edition is divided into three topics.

1.Changes and properties of matter.

2.Chemistry is an experiment-based science.

3.Step into the chemistry lab.

Unit 3 Water in Nature.

1. The composition of water.

On what basis can it be inferred that water is a compound composed of two elements, hydrogen and oxygen?

2. Elemental substances and compounds.

What are the similarities between elementals and compounds? What's the difference? Want to learn to differentiate? Give a few examples of each and write the chemical formula?

3. Understand the particulate nature of matter.

What are the different types of particles that make up matter? What is the relationship between them?

Fourth, the nature of the molecule.

What are the characteristics of a molecule? Give a few examples to prove that molecules are in constant motion? What are a few examples of intermolecular spacing?

5. Purification of water.

1) What is the difference between pure water and natural water? What is the difference between hard water and soft water?

2) What are the operations for purifying water? What is the most decontaminated operation?

3) What are the principles of water purification for alum and activated carbon?

4) What kind of mixtures can be separated by filtration? What is the meaning of "one sticker, two low, three reliance" in the operation essentials of filtration?

6. Water pollution.

What are the main ** of water pollution? How can it be prevented?

7. Save water.

Recognise the Conservation Symbol and list common water-saving practices in your daily life?