Tutor profile: Craig G.

What are three ways that humans produce excess carbon dioxide, and why is this an issue for our planet?

Humans produce excess carbon dioxide a number of ways. Some of the primary ways are through the burning of fossil fuels for electricity and transportation, eating a diet high in red meat, and deforestation. Excess carbon is an issue because carbon dioxide and other greenhouse gases in the atmosphere trap heat and prevent it from radiating back into space. An excess of these greenhouse gases is causing the planet's temperature to dramatically increase and resulting in significant changes to our climate.

Explain the difference between a chemical and a physical change, and describe which type of change is taking place when iron rusts.

The difference between a chemical and a physical change is in the composition of the substance. In a chemical change the composition of the substance undergoing a reaction actually changes; where as, in a physical change only the physical appearance or traits change, like color for example, but the actual composition of the substance remains the same. While a color change is often an example of a physical change, rust is an example of a chemical change because the actual composition of the iron is changed due to oxidation.

What is photosynthesis, and why is it important for life on Earth?

Photosynthesis is the process by which plants convert light energy, carbon dioxide, and water into chemical energy and oxygen that can be used by other organisms. It is important because it 1) produces the chemical energy or food that other living organisms need to carry out metabolic processes 2) removes carbon dioxide from the atmosphere 3) produces oxygen that all living things need for cellular respiration.