8th Grade Chemistry - Quiz 2: Endo/Exo, P Table, + Diagrams

To be able to…

Orange = repeat topics from last quiz that are fair game

Blue = new topics also on this quiz

Highlight = Learn Topics

• Can you compare the difference between an atom, an element, and a molecule?

• Can you identify the different equipment in a chemistry lab AND how to use them?

  • Beakers, flasks, graduated cylinders, pipettes, balances, hot plates, test tubes

• Can you explain which chemistry lab equipment and units of measurement (Celcius, mL, g) are used for measuring solids and liquids?

• Can you identify the difference between endothermic and exothermic reactions in regards to temperature and energy levels?

• Who created the modern Periodic Table of elements and why was his theory accepted?

• How is the periodic table organized AND how can you use these trends to predict certain properties of the elements?

  • Groups and Periods

  • Metals, Nonmetals, Metalloids

  • Solids, Liquids, Gases

  • Valence Electrons

  • Atomic Radius [optional]

• What are the 3 subatomic particles and what are their charges?

  • Why is a neutron important?

• How can you find the p+e-n?

• Can you draw a Bohr Diagram of an element?

• Can you draw a Lewis Dot Diagram of an element? What do the dots represent?

• What are the 4 families of the periodic table and where are they on the periodic table?

Topics that can be asked on any quiz all year:

• Identifying independent and dependent variables

• Graphing and analyzing graphs

• Writing hypotheses

ANSWERS:

1. Atom vs. Element vs. Molecule

• Atom: The smallest unit of matter, made up of protons, neutrons, and electrons. Example: A hydrogen atom (H).

• Element: A pure substance made of only one kind of atom. It’s found on the periodic table. Example: Oxygen (O).

• Molecule: Two or more atoms chemically bonded together. They can be the same or different elements. Example: H₂O (water) or O₂ (oxygen gas).

2. Chemistry Lab Equipment & Their Uses

• Beakers: Used to hold, mix, and heat liquids. Not great for precise measurements.

• Flasks (Erlenmeyer Flasks): Used to swirl and mix without spilling. Also good for heating liquids.

• Graduated Cylinders: Used to measure the volume of liquids accurately (in mL).

• Pipettes: Used to transfer small amounts of liquids precisely.

• Balances: Used to measure the mass of solids (in grams).

• Hot Plates: Used to heat substances.

• Test Tubes: Hold small amounts of substances for reactions and experiments.

3. Measuring Solids & Liquids

• Solids: Use balances to measure mass in grams (g).

• Liquids: Use graduated cylinders or pipettes to measure volume in milliliters (mL).

• Temperature: Use a thermometer (measured in Celsius (°C)).

4. Endothermic vs. Exothermic Reactions

• Endothermic: Absorbs energy/heat from surroundings. Temperature drops. Example: Photosynthesis.

• Exothermic: Releases energy/heat into surroundings. Temperature rises. Example: Combustion (burning wood).

5. The Modern Periodic Table

• Created by: Dmitri Mendeleev in 1869.

• Why Accepted: He arranged elements by atomic mass and left gaps for undiscovered elements, predicting their properties accurately. Later, the table was reorganized by atomic number, confirming his ideas.

6. Periodic Table Organization & Trends

• Groups (Columns): Elements in the same group have similar chemical properties because they have the same number of valence electrons.

• Periods (Rows): Elements in the same period have the same number of electron shells.

Element Properties:

• Metals: Left side, shiny, good conductors, malleable.

• Nonmetals: Right side, brittle, poor conductors.

• Metalloids: Along the zigzag line, have properties of both metals and nonmetals.

States of Matter:

• Solids, Liquids, Gases: Most elements are solid at room temperature, with a few gases (like oxygen) and only two liquids (mercury and bromine).

Trends:

• Valence Electrons: Increase across a period, stay the same down a group.

• Atomic Radius (Optional): Decreases across a period, increases down a group.

7. Subatomic Particles & Their Importance

• Protons (p⁺): Positive charge, found in the nucleus. Determine the element’s identity.

• Neutrons (n⁰): No charge, found in the nucleus. Important for stabilizing the atom.

• Electrons (e⁻): Negative charge, orbit the nucleus. Involved in chemical bonding.

Why are neutrons important?
They stabilize the nucleus. Without them, protons would repel each other due to their positive charges.

8. Finding p⁺, e⁻, and n⁰

• Protons (p⁺): Equal to the atomic number (found on the periodic table).

• Electrons (e⁻): Equal to protons in a neutral atom.

• Neutrons (n⁰): Subtract atomic number from atomic mass (mass number - atomic number).

9. Drawing Diagrams

• Bohr Diagram Prompt: Draw the nucleus with protons and neutrons inside. Then, add electrons in shells around the nucleus based on the element’s atomic number.

• Lewis Dot Diagram Prompt: Write the element’s symbol and place dots around it representing the number of valence electrons.

  • USE PERIODIC TABLE AND DRAW A COUPLE OF EXAMPLES

10. Four Families of the Periodic Table

1. Alkali Metals (Group 1): Very reactive, 1 valence electron.

2. Alkaline Earth Metals (Group 2): Reactive, 2 valence electrons.

3. Halogens (Group 17): Very reactive nonmetals, 7 valence electrons.

4. Noble Gases (Group 18): Inert gases, 8 valence electrons (except Helium with 2).