Question 1: Define density in terms of mass and volume, including its SI unit.

Answer: Density is the mass per unit volume of a substance, measured in kilograms per cubic metre (kg/m³).

Question 2: Explain why measuring density is important in identifying materials.

Answer: Measuring density helps identify materials because each material has a characteristic density, distinguishing it from others.

Question 1: What are the main variables that need to be controlled during a density experiment?

Answer: The main variables include temperature (to ensure constant conditions), and the accuracy of measurements of mass and volume.

Question 2: Describe the method to measure the volume of an irregular solid object.

Answer: The volume of an irregular object can be measured using water displacement; the increase in water level indicates the volume.

Question 1: A metal block has a mass of 450 grams and a volume of 150 cm³. Calculate its density in kg/m³.

Answer: Density = mass/volume = 0.45 kg / 0.00015 m³ = 3000 kg/m³

Question 2: An object has a density of 2.7 g/cm³ and a mass of 27 grams. What is its volume in cm³?

Answer: Volume = mass/density = 27 g / 2.7 g/cm³ = 10 cm³

Question 1: List three safety precautions that should be followed when handling liquids and solids during the density experiment.

Answer: Wear safety goggles, handle chemicals carefully to avoid spills, and ensure proper disposal of materials.

Question 2: Identify two variables that must be kept constant during the experiment and explain why.

Answer: Temperature and measurement accuracy must be kept constant to ensure consistent and reliable results.

Question 1: A student measures the mass of an aluminium cube as 270 grams and its volume as 100 cm³. How does this value compare to the known density of aluminium (2.7 g/cm³)? Is this consistent? Explain.

Answer: The calculated density is 2.7 g/cm³ (270 g/100 cm³), which matches the known density of aluminium, indicating consistent and accurate measurement.

Question 1: Describe how you would perform an experiment to determine the density of a new plastic material. Include the steps, variables to control, and safety precautions. Justify each step based on scientific principles. (6 marks)

Answer: To determine the density of a new plastic, first measure its mass using a balance, ensuring it is dry and clean. Then, measure its volume by submerging it in water and recording the water displacement, making sure to control the water temperature to prevent expansion. Repeat measurements for accuracy. Control variables such as temperature and ensure the plastic is fully submerged without air bubbles. Use safety goggles and handle water carefully to prevent spills. Calculate density using the formula: density = mass/volume. Justify steps by explaining how each measurement relates to the particle model and the importance of controlling variables for accuracy.

Question 1: How is density measurement important in the shipping industry, particularly in relation to cargo safety and efficiency?

Answer: Density measurement helps determine the weight-to-volume ratio of cargo, ensuring ships are not overloaded and are balanced for safe navigation, while also maximising cargo space for efficiency.