Density
Define Density and mention it's SI unit.
Density = M/V(mass per unit volume)
S.I unit = kg/m3
What is a measuring cylinder?What capacities is it available in?
A measuring cylinder is a piece of laboratory glassware used to measure the volume of liquids accurately. It is typically a tall, narrow, cylindrical container with a flat base and a spout for pouring.
50, 100, 200, 500mL
Name the law of floatation.
The law of flotation states that an object will float if the buoyant force (the upward force exerted by the fluid) on it is equal to or greater than its weight. This principle is a consequence of Archimedes' principle, which states that any object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the object. Thus, an object will float if its weight is less than or equal to the weight of the fluid it displaces.
A metal block has a mass of 200 grams and a volume of 50 cubic centimeters. What is its density?
Solution:
Density = Mass / Volume
Density = 200 g / 50 cm³
Density = 4 g/cm³
Explain the exception of density and mention the density increase or decrease with mention of temperature.
Water contracts from 0-4 celcius and expands on heating above 4 celcius. So the density of water increases from 0-4 cel cius and then decreases above 4 celsius.
Describe how a measuring cylinder is used.
A measuring cylinder, also known as a graduated cylinder, is a common laboratory instrument used to measure the volume of a liquid with precision. Here’s how you use one:
Select the Right Cylinder: Choose a measuring cylinder with an appropriate volume range for your needs. They come in various sizes, from 10 mL to 2 liters or more.
Place on a Flat Surface: Ensure the measuring cylinder is on a flat, level surface to get an accurate reading. This helps prevent errors caused by tilting.
Pour the Liquid: Carefully pour the liquid into the measuring cylinder. If you’re transferring from another container, do it slowly to avoid spills and splashes.
Check the Meniscus: Look at the liquid level at eye level to get an accurate reading. The liquid will curve slightly at the edges, forming a meniscus. For most liquids, you should read the bottom of the meniscus to determine the volume.
Read the Measurement: Observe the graduation marks on the cylinder. Each mark represents a specific volume. Read the value at the bottom of the meniscus to determine the liquid’s volume.
Record the Measurement: Note the volume as indicated by the graduation marks.
Clean and Store: After use, clean the measuring cylinder thoroughly and store it properly to prevent contamination and damage.
Why is it easier for a person to in in sea water than in river water?
It's easier for a person to float in seawater than in river water because seawater is denser than freshwater. This increased density in seawater comes from its higher salt content. Here’s how it affects floating:
Density and Buoyancy: Seawater’s greater density means it provides more buoyant force for the same volume of water displaced. This is because the weight of the seawater displaced is greater than the weight of the freshwater displaced.
Easier Floating: Due to the increased buoyant force, you need to displace less of the seawater to balance your weight and stay afloat. In contrast, in river water (which is less dense), you need to displace more water to achieve the same buoyant force and stay afloat.
If a piece of iron has a mass of 400 grams and a volume of 50 cubic centimeters, and a piece of wood has a mass of 200 grams and a volume of 100 cubic centimeters, which one is denser?
Iron:
Density = Mass / Volume
Density = 400 g / 50 cm³
Density = 8 g/cm³
Wood:
Density = Mass / Volume
Density = 200 g / 100 cm³
Density = 2 g/cm³
The piece of iron is denser than the piece of wood.
Define Relative Density with it's unit.
Relative Density is the ratio of density of the substance to the density of water.
There is no unit.
What is a measuring beaker? State it's capacities.
A measuring beaker is a common piece of laboratory glassware used for measuring and mixing liquids. It is typically cylindrical with a flat bottom and a spout for easy pouring. Beakers come in various sizes and are marked with graduated scales to indicate volume.
Capacities
Measuring beakers are available in a range of sizes, commonly including:
Why does a large ship made of steel float on water, while a small rock sinks?
A large ship floats because it is designed with a hull that displaces a large volume of water, creating an upward buoyant force greater than its weight. The steel ship’s overall density is less than the density of water. A small rock, however, does not displace enough water to create sufficient buoyant force and sinks.
A metal sample has a mass of 150 grams and a volume of 50 cubic centimeters. If the density of water is 1 g/cm³, what is the relative density of the metal?
Density of the metal = Mass / Volume
Density of the metal = 150 g / 50 cm³
Density of the metal = 3 g/cm³
Relative Density = Density of the metal / Density of water
Relative Density = 3 g/cm³ / 1 g/cm³
Relative Density = 3
How to determine the density of an irregular solid?
Displacement method
Define Eureka Can. Draw a diagram of a Eureka can.
How does it work?
A Eureka Can is a laboratory tool used to measure the volume of an irregularly shaped object by determining the volume of water it displaces. It is also referred to as an overflow can.
How It Works
Initial Setup:
Submerge Object:
Displaced Water Collection:
Measure Displaced Water:
Why does ice float on water? How can a submarine dive or rise to the surface of water when desired?
Why Ice Floats on Water
Ice floats on water because it is less dense than liquid water. This happens due to the unique properties of water when it freezes:
Density Difference: Because ice has a lower density than liquid water, the buoyant force (upward force) exerted by the water on the ice is greater than the weight of the ice, causing it to float.
How a Submarine Dives or Rises to the Surface
A submarine can dive or rise to the surface by adjusting its buoyancy, which is controlled through its ballast system. Here’s how it works:
1. Diving
Ballast Tanks: To dive, a submarine fills its ballast tanks with water. These tanks are located in various parts of the submarine and can be filled with water or air.
Increasing Weight: When the tanks are filled with water, the submarine's overall density increases, causing it to sink as its weight becomes greater than the buoyant force.
2. Rising to the Surface:
Ballast Tanks: To rise, the submarine expels the water from the ballast tanks and replaces it with air (often using compressed air).
Decreasing Weight:As the tanks are filled with air, the submarine’s density decreases because air is much less dense than water. This reduction in density makes the submarine lighter, and it starts to rise as the buoyant force exceeds its weight.
A solid object has a mass of 500 grams and displaces 200 cubic centimeters of water when submerged. Determine the density of the object.
To determine the density of the solid object, you need to use the formula for density:
Density=Mass/Volume
Given:
Substitute these values into the formula:
Density=500 grams/200 cubic centimeters
Density=2.5 grams per cubic centimeter
So, the density of the solid object is 2.5 grams per cubic centimeter
Why does relative density has no unit?
How to determine the density of the liquid?
The relative density does not have a unit because it is a ratio of two-dimensionally same quantities.
To determine the density of a liquid, you can follow these steps:
Measure the Mass: Use a precise scale or balance to weigh a container (such as a graduated cylinder) when it is empty. Record this mass. Then, fill the container with the liquid and weigh it again. Subtract the mass of the empty container from the mass of the container with the liquid to get the mass of the liquid.
Measure the Volume: Measure the volume of the liquid using the graduated markings on the container, such as a graduated cylinder or pipette. Ensure you read the measurement at eye level to avoid parallax errors, and be consistent in measuring at the liquid's meniscus (the curve at the surface of the liquid).
Calculate Density: Use the formula for density:
Density=Mass/VolumeDefine Density bottle. Draw a diagram of a density bottle. How do you determine the density of a liquid using a density bottle?
A density bottle is a laboratory apparatus used to determine the density of liquids with high precision. It typically consists of a glass bottle with a precisely known volume and a stopper that fits snugly to prevent any leakage. The bottle is often used to measure the mass of a known volume of liquid and, from this, calculate the liquid's density.
To determine the density of a liquid using a density bottle, follow these steps:
Clean and Dry the Bottle: Ensure the density bottle is clean and completely dry before use to avoid contamination or errors in measurement.
Weigh the Empty Bottle: Weigh the empty density bottle with its stopper using a precise balance. Record this mass as M1
Fill the Bottle with the h20: Carefully fill the bottle with the water to be tested. The liquid should be filled to the neck of the bottle. Replace the stopper securely to prevent any leakage.
Fill the Bottle with the liquid: Weigh the bottle with the liquid and stopper. Record this mass as M3.
Calculate the Density of the Liquid: Density =
(M3-M1)g/(M2-M1)cm3
State the principal of floatation with three possibilities and diagrams.
The principle of flotation states that:
An object placed in a fluid will float if the buoyant force acting on it is equal to or greater than the weight of the object.
Three possibilities : The weight of the body is greater than the buoyant force.
The weight of the body is equal to the buoyant force.
The weight of the body is less than the buoyant force.
A hollow sphere is filled with a gas that has a density of 0.5 grams per liter. If the sphere has a volume of 2 cubic meters, what is the mass of the gas inside the sphere?
To find the mass of the gas inside the sphere, follow these steps:
Convert the volume of the sphere from cubic meters to liters:
Calculate the mass of the gas:
Convert the mass from grams to kilograms (if needed):
So, the mass of the gas inside the sphere is 1000 grams or 1 kilogram.