Chemical Change- Sience

Question 1

Basic concept of atoms

Answer 1

Basic Concept: All matter is made up of tiny particles known as atoms.

Question 2

Structure of an Atom:

Answer 2

Nucleus: Contains protons (positively charged) and neutrons (neutral).
• Electrons: Negatively charged particles that orbit the nucleus in shells/energy levels.

Question 3

Atomic Number and Mass Number:

Answer 3

Atomic Number: The number of protons in an atom (also equal to the number of electrons).
• Mass Number: The total number of protons and neutrons in an atom.

Question 4

To find the number of neutrons:

Answer 4

Subtract the atomic number from the mass number.

Question 5

Electron Configuration:

Answer 5

For the first 20 elements, electrons fill shells as follows:
• 1st shell: 2 electrons
• 2nd shell: 8 electrons
• 3rd shell: 8 electrons
• 4th shell: up to 18 electrons (though for the first 20 elements, only 2 or 8 will typically fill)

Question 6

Periodic table first 20

Answer 6

Atomic Number,Element,Symbol
1,Hydrogen,H
2,Helium,He
3,Lithium,Li
4,Beryllium,Be
5,Boron,B
6,Carbon,C
7,Nitrogen,N
8,Oxygen,O
9,Fluorine,F
10,Neon,Ne
11,Sodium,Na
12,Magnesium,Mg
13,Aluminum,Al
14,Silicon,Si
15,Phosphorus,P
16,Sulfur,S
17,Chlorine,Cl
18,Argon,Ar
19,Potassium,K
20,Calcium,Ca

Question 7

Transition Elements:
•

Answer 7

Copper (Cu), Iron (Fe), Tin (Sn), Lead (Pb), Gold (Au), Mercury (Hg), Silver (Ag), Zinc (Zn).

Question 8

Groups and Periods:
•

Answer 8

Groups: Vertical columns in the periodic table (e.g., Group 1, Group 2, Group 17).
• Periods: Horizontal rows, indicating the number of electron shells.
3. Similar Properties: Elements in the same group have similar chemical properties due to the same number of valence electrons.

Question 9

Chemical Change

Answer 9

process that results in the formation of new substances (e.g., rusting of iron, combustion).
• Examples:
• Iron reacting with oxygen to form iron oxide (rust).
• Burning wood producing ash and gases.

Question 10

Physical Change:

Answer 10

A change that does not alter the chemical composition of a substance (e.g., melting, boiling).
• Examples:
• Ice melting to water.
• Dissolving sugar in water.

Question 11

Comparison:
of physical and chimcial change

Answer 11

Physical Change: The substance changes in form or appearance, but its chemical makeup stays the same (like melting or breaking something).
• Chemical Change: A new substance is formed with different properties. This usually can’t be reversed easily (like rusting or burning).

Question 12

Chemical Equations

Answer 12

1. Writing Word Equations: Represents chemical reactions using the names of the reactants and products.
   • Example:
   • Magnesium + Oxygen → Magnesium Oxide.

Question 13

The Fire Triangle

1.

Answer 13

Three Components:
• Heat: Energy source.
• Fuel: Material that burns.
• Oxidizer: Usually oxygen in the air.
2. Putting Out Different Types of Fires:
• Class A (solid combustibles): Water or foam.
• Class B (flammable liquids): Foam, CO2, or dry chemical.
• Class C (electrical): CO2, dry chemical; do not use water.
• Class D (metals): Special powders designed for metal fires.

Question 14

Formation of Ions: metal

Answer 14

Formation of Ions:
• Metal Atoms: Tend to lose electrons and form positively charged ions (cations).

Question 15

Formation of Ions:

•	Non-metal Atoms:

Answer 15

• Non-metal Atoms: Tend to gain electrons and form negatively charged ions (anions).

Question 16

Chemical Formulas:

Answer 16

Used to represent the number of atoms in a molecule or ionic compound.
• Example: In NaCl (sodium chloride), there is 1 sodium atom and 1 chlorine atom.

Question 17

Cation Formation:
•

Answer 17

Cations form when atoms lose electrons, leaving them with a positive charge.

Question 18

Anion Formation:

Answer 18

Anions are tiny particles that have a negative charge because they gain extra electrons from other atoms.