Natural gas is a fuel that is used for heating and cooking in many homes and buildings. It is composed of almost pure methane, CH₄, and burns with a hot, blue flame. The chemical equation for the burning of methane is show below : CH4 + 2O2 → CO2 + 2H2O

Describe the burning of methane as a chemical reaction by explaining the following :

1. How can you tell from the chemical equation that this is a chemical reaction and not just a physical change ?

2.What observations would you see that indicate a chemical reaction?

3.is it an exothermic or endothermic reaction? What observation support your choice ?

The earth's moon is unusually large. two popular theories of the moon's origin include the "sister world" hypothesis, which states that the moon formed from the same materials as the earth, near enough to the earth that they fell into orbit around each other. a second theory is the "capture" hypothesis, in which the moon formed elsewhere in the solar system, and the earth's gravity pulled it into its orbit. studies of what the moon is made of indicate that some of its materials had to come from the earth or from the same area of the solar system where the earth had formed. at the same time, the moon does not contain much of the material that makes up the earth's core, so the moon could not have formed from the same materials as the earth. how do the two facts above affect the described theories of the moon's origin? a. they show that scientists will never agree on where the moon came from. b. they show that more experiments on moon formation need to be done. c. they show that no theory accounts for the existence of the moon. d. they show that neither theory is complete and entirely correct.

If you burn 10 kilograms of wood in a fire (combustion) what is the weight of the products after the fire has finished burning the wood?

Ascientist is measuring the pressure that is exerted by each of the following gases in the atmosphere: carbon dioxide, oxygen, and nitrogen. which term most likely describes what she is measuring?