Test: Physical Quantities and Measurement - Class 8 MCQ

An object with a density of 0.5 g/cm³ will float in a liquid with a density of 0.8 g/cm³ because it is less dense than the liquid. This principle is essential in applications involving flotation and buoyancy.

The relative density of a substance with a density of 7.8 g/cm³ compared to water (1 g/cm³) is 7.8. This means that the substance is 7.8 times denser than water, explaining why it would sink.

When the mass of an object increases while the volume stays the same, the density increases. This is because density is directly proportional to mass; as mass increases, density must also increase if volume does not change.

The volume of an irregular solid can be determined using the displacement method. This involves submerging the solid in water and measuring the volume of water displaced, which equals the volume of the solid.

The first step in measuring the density of a liquid is to measure its mass using a beam balance. After determining the mass, the volume can be measured, and density can then be calculated.

The density of water decreases as it freezes, which is why ice floats on water. This decrease in density is unusual for substances, as most become denser when solidified.

A density bottle is significant because it ensures that a fixed volume of liquid is measured. This precision is vital for accurately calculating the density of the liquid in question.

Ice, with a density of 0.917 g/cm³, will float in water because its density is less than that of water (1 g/cm³). This characteristic of ice is crucial for aquatic life, as it insulates the water below.

The mass of the liquid is 45 g - 20 g = 25 g. The density is calculated as: Density = Mass/Volume = 25 g / 50 cm³ = 0.5 g/cm³.

Generally, the density of a substance decreases when it is heated because its volume tends to increase. However, water is an exception, as its density increases when heated from 0°C to 4°C before decreasing at higher temperatures.

The relative density of a substance is the ratio of its density to the density of water. This helps in determining how a substance will behave in water, such as whether it will float or sink.

The SI unit of density is kg/m³. This unit expresses mass in kilograms and volume in cubic meters, providing a standard way to quantify how dense a substance is.

Objects with higher density than water sink because the buoyant force exerted by the water is insufficient to support them. The weight of the object exceeds the upward buoyant force, causing it to sink.

A cube ruler is not typically used to measure the volume of liquids. Instead, measuring cylinders, density bottles, and beakers are specifically designed for that purpose, with clear markings for accurate measurement.

Submarines use the principle of buoyancy by controlling the density of their internal air tanks. When they fill these tanks with water, their density increases, causing them to sink. Conversely, when filled with air, their density decreases, allowing them to rise.

An object will float in a liquid when its density is equal to the liquid's density. At this point, the buoyant force matches the weight of the object, resulting in it floating at the surface.

Cork has a density of approximately 0.25 g/cm³, which is less than that of water (1 g/cm³). This lower density allows cork to float on water, making it useful in various applications.

The buoyant force is the upward force exerted by a fluid on an object submerged in it. This force is responsible for the object's ability to float and is equal to the weight of the fluid displaced by the object.

An object will sink in water if its density is greater than that of water (1 g/cm³). Conversely, if its density is less than water, it will float. This principle is fundamental to understanding buoyancy.

Density is defined as the mass of an object divided by its volume. This relationship helps us understand how tightly packed the matter in an object is, which is crucial in determining whether it will float or sink in a liquid.