Physics Chapter 3: Density

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Questions and Answers

Which factor contributes to the density of objects in the sea compared to those on land?

Presence of impurities in water

Concentration of air in the rocks

Temperature variations

Density of sea rocks versus land rocks (correct)

What is the relative density of iron, given its density is $7800 ext{ kg/m}^3$ and the density of water is $1000 ext{ kg/m}^3$?

1.5

0.125

7.8 (correct)

10.8

What does a higher API gravity indicate about a petroleum liquid?

It is denser than water

It contains more impurities

It will sink in water

It is lighter than water (correct)

Which statement correctly defines relative density?

The comparison of a body's density with that of a reference body, usually water Signup and view all the answers

An object that does not sink in the Dead Sea is likely due to which factor?

Increased concentration of impurities Signup and view all the answers

What is the correct formula to calculate density?

Density = mass / volume Signup and view all the answers

Which method is used to find the volume of irregular shapes?

Displacement method Signup and view all the answers

Which of the following statements about density is true?

An object with closer atoms will have a higher density. Signup and view all the answers

How can mass be determined according to the provided information?

Using a pan balance Signup and view all the answers

Why is density considered a measure of compactness?

It factors in both mass and volume of a substance. Signup and view all the answers

What is the first step in calculating the density of a regular-shaped object?

Determine the mass of the object Signup and view all the answers

Which of the following substances is likely to have the highest density?

Iron Signup and view all the answers

What defines relative density?

It compares the density of a substance to water. Signup and view all the answers

What is the primary formula used to calculate density?

Density = mass / volume Signup and view all the answers

If a stone has a mass of 20 g and its density is 5 g/ml, what is its volume?

4 ml Signup and view all the answers

Why can deep sea fishes control their density?

They can change the volume of air in their bodies. Signup and view all the answers

Which substance is less dense than water, allowing it to float?

Ice Signup and view all the answers

When the temperature of a gas increases, what happens to its density?

Density decreases. Signup and view all the answers

What would happen to a steel bolt placed in mercury?

It will float. Signup and view all the answers

If the mass of a sphere with a diameter of 6 cm is 70 g, how would you express its density in kg/m³?

17500 kg/m³ Signup and view all the answers

If an object with a mass of 700 g has a density of 350 kg/m³, what is its volume in m³?

0.002 m³ Signup and view all the answers

Study Notes

Chapter 3: Density

Lesson Outcomes:
- Demonstrate understanding of density and relative density.
- Determine density of regular and irregular objects.
Keywords:
- Force, mass, volume, density, relative density.
Learning Objective:
- Demonstrate understanding of force and pressure.

Submarine Functionality

Floating Submarine:
- Ballast tanks filled with air.
Submerging Submarine:
- Vent holes open.
- Air escapes as tanks fill with water.
Rising Submarine:
- Vent holes closed.
- Compressed air pumped into tanks forces water out.

Density Definition

Density: Amount of matter per unit volume.
Density Formula: Density = Mass / Volume (ρ = m/V)

Density Examples

Density Comparison (Cork, Wood, Metal):
- Cork < Wood < Metal (cork has lowest density).
Gases:
- Hydrogen: 0.089 kg/m³
- Oxygen: 1.43 kg/m³
- Carbon Dioxide: 1.96 kg/m³
Liquids:
- Alcohol: 789 kg/m³
- Water: 1000 kg/m³
- Mercury: 13534 kg/m³
Solids:
- Aluminium: 2700 kg/m³
- Steel: 7500 kg/m³
- Uranium: 18800 kg/m³

Density in Different States of Matter

Gases:
- Fill the available space.
- Larger volume = lower density.
- Temperature affects expansion and density.
- Warm air rises, cold air sinks.
Liquids:
- Ice is less dense than water.
- This explains why lakes/ponds freeze from the top down.
Solids:
- Materials can be identified and separated by density.
- Example: Steel bolt floats on mercury.

Factors Affecting Density

Temperature: Higher temperature = lower density (hot air rises).
Pressure: Higher pressure = higher density (sea rocks denser than surface rocks).
Impurities/Concentration: Impurity can change density. Example: Dead Sea.
Atoms in Material: Heavier atoms = higher density (gold is much denser than common materials).

Relative Density

Relative Density (Specific Gravity):
- Ratio of a substance's density to the density of a reference substance (usually water).
- Density of iron: 7800 kg/m³
- Density of water: 1000 kg/m³
- Relative Density of iron: 7.8
API Gravity:
- Inverse measure of petroleum liquid density relative to that of water
- Above 10API = lighter (floats)
- Below 10API = heavier (sinks)

Methods to Determine Density

Regular Shapes:
- Find mass using a pan balance.
- Find volume with appropriate geometric formula (e.g., V = L × W × H for rectangular prism, V= πr³ for a sphere.)
- Density = Mass / Volume.
Irregular Shapes:
- Find mass using a pan balance.
- Find volume using displacement method (water displacement in a graduated cylinder).
- Density = Mass / Volume.

Project-1: Finding Density of Given Objects

Objective: Calculating the density of provided objects.

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Description

Explore the concept of density through various examples and its application in understanding buoyancy with submarines. Learn how to calculate density for regular and irregular objects while comparing the densities of different materials, including gases and liquids.