SCI 1100: Density, Energy, and Thermodynamics Key Concepts

What is density and how is it calculated?

Density is the mass of an object divided by its volume (Density = Mass/Volume).

How do the densities of objects of different sizes but the same material compare?

The densities of objects made of the same material are the same regardless of their size.

What is a fluid?

A fluid is a substance that can flow, and the two common states of matter that are fluids are liquids and gases.

What is pressure?

Pressure is the force applied per unit area.

Do equal forces always apply equal pressures?

No, equal forces do not always apply equal pressures; pressure also depends on the area over which the force is applied.

What happens to pressure as you go deeper in a fluid?

Pressure increases as you go deeper in a fluid.

What is buoyant force?

Buoyant force is the upward force exerted by a fluid on an object submerged in it.

What causes buoyant force?

Buoyant force is caused by the pressure difference between the top and bottom of an object submerged in a fluid.

In which direction does buoyant force push?

Buoyant force pushes upward.

What does buoyant force equal?

Buoyant force equals the weight of the fluid displaced by the object.

What principle defines the buoyant force?

Archimedes' Principle defines that the buoyant force equals the weight of the fluid displaced.

How can you determine if a solid or liquid will float or sink?

An object will float if its density is less than that of the fluid; it will sink if its density is greater.

What is the density of water?

The density of water is approximately 1 g/cm³.

How do weight and buoyant force determine if an object floats?

An object floats if its weight is equal to the buoyant force; the amount submerged depends on the ratio of these forces.

What are energy and work?

Energy is the capacity to do work, and work is done when a force moves an object. Their standard unit is the Joule.

What are the two major types of energy?

The two major types of energy are kinetic energy and potential energy.

What are two factors that affect kinetic energy?

Kinetic energy is affected by the mass of the object and its velocity.

What are two factors that affect potential energy?

Potential energy is affected by the mass of the object and its height above a reference point.

What is thermodynamics?

Thermodynamics is the study of heat, energy, and work, and how they interact.

What are the three laws of thermodynamics?

The first law states energy cannot be created or destroyed; the second law states entropy of an isolated system always increases; the third law states as temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

How do nuclear reactions relate to the first law of thermodynamics?

Nuclear reactions demonstrate the conversion of mass into energy, illustrating the law of conservation of energy.

What is entropy?

Entropy is a measure of disorder in a system, and it generally increases over time.

How can entropy decrease?

Entropy can decrease locally in a system through energy input, but the total entropy of the universe still increases.

What is the Kelvin temperature scale?

The Kelvin scale is an absolute temperature scale with no negative numbers, where 0 K is absolute zero.

What determines the temperature of an object?

The temperature of an object is determined by the average kinetic energy of its molecules.

What happens molecularly when objects of different temperatures come in contact?

Heat flows from the hotter object to the cooler one until thermal equilibrium is reached.

What does absolute zero mean molecularly?

At absolute zero, molecular motion theoretically ceases.

What are the three ways heat can be transferred?

Heat can be transferred by conduction, convection, and radiation; conduction is the least efficient, and radiation can occur through a vacuum.

How are temperature and density generally related?

Generally, as temperature increases, density decreases; this principle explains how thermometers work.

What is unique about water and density?

Water is unique because it is less dense as a solid (ice) than as a liquid, allowing ice to float.