Chemistry 8 Lesson 6: Elements and Compounds – Molecules
1. Summary of theory
1.1. Single substance
a. What is a single element?
Definition: Substance made up of one chemical element.
Metallic element: Conducts electricity, conducts heat, has metallic luster.
– Non-metallic element: Does not conduct electricity, conducts heat, has no metallic luster.
*Conclusion: Substance made up of 1 chemical element. Consists of 2 types:
b. Structural features
– Metallic element: Atoms are arranged closely together and in a definite order.
– Non-metallic elements: Atoms bonded to each other by a certain number (Usually 2).
a. What is a compound?
– Define: Compounds are substances made up of 2 or more chemical elements.
+ Inorganic compounds: H2O, NaOH, NaCl, H2SO4…
+ Organic compounds: ONLY4 (Methane), CtwelfthH22O11 (road C2H2 (Acetylene), C2H4 (Ethene)…
b. Structural features
– In compounds: Elements bonded together in a certain ratio and order
A molecule is a particle representing a substance, consisting of a number of atoms bonded together and fully expressing the chemical properties of the substance.
b. Mass molecule
Molecular mass is the mass of a molecule in units of carbon.
1.4. Natural state
Each sample is a very large collection of atoms or molecules.
– Depending on the physical conditions, it can be in 3 states: solid, liquid, gas. In the gas state, the particles are far apart.
2. Illustrated exercise
2.1. Form 1: Observing patterns of elements and compounds
Observe the symbolic pattern of substances in Figure 1.25 and complete the following table
2.2. Form 2: True and false statements
Based on the figure below, indicate that the following statement is true. Water and ammonia:
A. They are all pure substances
B. All contain hydrogen atoms
C. All contain atoms of the same type.
D. There are 3 atoms in the molecule.
H2O and SMALL3 are compounds, so statement A is false.
H2O and SMALL3 All contain hydrogen atoms, so statement B is correct.
H2O contains H and O are different types of atoms, SMALL3 contains H and N are different types of atoms, so the statement C is incorrect.
H2O has 3 atoms in the molecule, SMALL3 There are 4 atoms in the molecule, so statement D is incorrect.
2.3. Form 3: Explain the phenomenon
Based on the molecular distribution when the substance is in different states, explain why:
a) Liquid water spontaneously spreads on the tray.
b) One milliliter of liquid water when converted to vapor again occupies a volume of about 1300 ml (at room temperature).
a) When the water is in the liquid state, the water molecules are close together and slide over each other, so the liquid water spreads out on the tray.
b) Although the number of water molecules is the same, water in the vapor state has a very large volume compared to when it is in the liquid state. The reason is due to the distribution of molecules: in the liquid state, the water molecules are right next to each other, sliding over each other; In the vapor state, the water molecules are very far apart, moving quickly and in different directions.
3.1. Essay exercises
Question 1: Compare elements and compounds?
Verse 2: Calculate the molar mass of the following substances: HCl, SO2, NaCl, KOH?
Question 3: Choose the given substances to fill in the blanks in the following sentences:
1…………….. is the main component of coal.
2. Expensive jewelry made from ……………..
3. Electrical wires are usually made from …………. covered with a layer of plastic.
4. Air consists of many gases, of which …………………………… 20% by volume.
The substances we just mentioned above: copper metal, gold metal, oxygen gas, carbon are called elements. So what is a single element?
Verse 4: What is the molecular model of the element?
3.2. Multiple choice exercises
Question 1: Is it correct to say the following (multiple answers can be selected)
A. Water molecule consists of elements hydrogen and oxygen
B. Chlorine is a metal
C. SMALL3 Odorless, colorless compound
D. Graphite is composed of the element C
Verse 2: Classification of organic and inorganic compounds: SMALL3, ONLY3COONa, P2O5, CuSO4,6HtwelfthO6, lead
A. Inorganic: SMALL3, P2O5, Lead
Organic: ONLY3COONa, OLD6HtwelfthO6
B. Inorganic: CuSO4, NS3
C. Inorganic: graphite, CuSO4, NS3, P2O5
D. There is no correct answer
Question 3: Calculate the molar mass of CH4 and THEY2O
A. ONLY4= 16 pts, H2O=18 ptC
B. ONLY4= 15 pts, H2O=17 ptC
C. ONLY4= HOW2O=18 ptC
D. Cannot calculate molecular mass
Verse 4: Choose the wrong answer:
A. Carbon dioxide is made up of 1 C element and 2 O . elements
B. Water is a compound
C. Table salt does not contain chlorine ingredients
D. There are 2 types of compounds, organic and inorganic
Question 5: The molecular mass of Cu is several times that of the molecular mass of Hydrogen
A. 4 times
B. 2 times
C. 32 times
D. 62 times
After studying this lesson, you will know:
- Elements are substances made up of one chemical element.
- Compounds are substances that are made up of two or more chemical elements.