Question 1: Define density in your own words and explain why it is an important property in the particle model of matter.

Answer: Density is the mass of a substance per unit volume, usually expressed in grams per cubic centimeter (g/cm³). It helps determine how tightly particles are packed together in a material, which influences its buoyancy, stability, and material properties.

Question 2: What is the formula used to calculate the density of an object? Include the units typically used for each quantity.

Answer: Density = Mass / Volume, where mass is in grams (g) and volume is in cubic centimeters (cm³).

Question 3: A block of aluminum has a mass of 270 grams and a volume of 100 cm³. Calculate its density.

Answer: Density = 270 g / 100 cm³ = 2.7 g/cm³

Question 4: Which of the following materials has the highest density? A) Water B) Aluminum C) Sulfur D) Cotton

Answer: B) Aluminum

Question 5: Fill in the blank: An object with a mass of 500 grams and a volume of 250 cm³ has a density of ______ g/cm³.

Answer: 2

Question 6: Explain how the particle model helps to understand why different materials have different densities.

Answer: The particle model suggests that matter is made up of tiny particles that are constantly moving and are packed together at different densities. Materials with tightly packed particles have higher densities because more mass is concentrated in a given volume, while materials with loosely packed particles have lower densities. Changes in temperature, pressure, or material type affect how particles are arranged, influencing the overall density.

Question 7: Describe a simple experiment to determine the density of a solid object. Include the steps and safety precautions.

Answer: To determine the density of a solid object, first measure its mass using a balance. Then, find its volume by submerging it in a graduated cylinder filled with water and recording the water level before and after submersion. The volume is the difference in water levels. Calculate density using the formula: density = mass / volume. Safety precautions include handling the balance carefully, avoiding water spillage, and ensuring the object is dry before weighing.

Question 8: A piece of sulfur has a mass of 16 grams and a volume of 8 cm³. What is its density? Show your work.

Answer: Density = 16 g / 8 cm³ = 2 g/cm³

Question 9: In everyday life, why is understanding the density of materials useful? Provide two examples.

Answer: Understanding density helps in choosing materials for specific purposes, such as selecting lightweight materials for aircraft or dense materials for ballast. It also explains why objects float or sink in water, which is important in designing ships and submarines.

Question 10: Compare the densities of water and aluminum and explain why a boat made of aluminum can float on water.

Answer: Water has a density of about 1 g/cm³, while aluminum's density is approximately 2.7 g/cm³. Despite aluminum being denser than many solids, a boat made of aluminum can float because it displaces a volume of water equal to its weight, according to Archimedes' principle. The overall density of the boat (including air inside) is less than water, allowing it to float.