Presents many interesting pieces of information from the history of pi.

Explains and demonstrates how to calculate the percent difference using a formula.

Explains and demonstrates how to calculate the percent change using a formula.

Explains what a parabola is and the vocabulary used to describe one and gives several examples of parabolas in real life.

Describes six levels of organization in the biological world - individual species, population, community, ecosystem, biome, and biosphere.

Discusses the cause of a hailstorm, the impact, and some famous hailstorms.

Presents a map and an alphabetical list of all the European countries and their capital cities.

Discusses the geography of Europe and presents a table of 51 European countries and their capitals and a second table of 12 autonomous regions and their capitals.

Explains what thermal energy is, describes some different types, and presents facts about each type.

Explains what potential energy and chemical potential energy are and gives examples of the latter.

Explains what kinetic and potential energy are and how they differ.

Presents interesting information about rainforests and the importance of preserving them.

Explains the roles of consumers, producers, and detrivores or decomposers and how energy flows through the different levels of the energy pyramid of a tropical rainforest.

Describes five types of landforms found in a tropical rainforest.

Explains what mutualism, commensalism, and parasitism are.

Discusses the history of the hydrogen bomb, how it works, countries that have the hydrogen bomb, efforts to prevent its misuse, and interesting facts about it.

Discusses the pros and cons of nuclear weapons and provides a list of facts about them.

Discusses the physical geography of the Sahara Desert, the climate, its landforms, the plants and animals that live there, and some of the people who live there or visit.

Describes how a food chain works in a desert and how the Mojave desert food chain works in particular.

Describes the layers of a rainforest, adaptations plants have made, and animals that live there.

Explains what a food web is, the complexity of one in a rainforest, and how energy flows through a food web.

Presents the formula and an example showing how to find the cross-sectional area of a cylinder. In this case, it is the same as the surface area for the circular faces.

The modern periodic table has evolved over a long period of time as new discoveries have been made. Learn about the contributions made by different scientists to its development.

Describes each of the five layers of the atmosphere from the troposphere, which is closest to the Earth, up to the outermost one, the exosphere.