consider the combustion of methane in oxygen (a reaction we've seen when we've lit soap bubbles on fire), which is a highly exothermic reaction.: true or false
1. once the activation energy has been reached increasing the concentration of methane and oxygen will increase the rate of the reaction.
2. a successful collision (one that leads to the combustion of methane) will will not need to meet the activation energy due to the extreme exothermic nature of the reaction.
3. once the activation energy has been reached, increasing the temperature will have no effect on the rate of the reaction.
4. a mixture of methane and oxygen can be kept in the same container indefinitely at room temperature with no change because the collisions taking place between the molecules do not have enough energy to reach overcome the reaction barrier.

the cold front replaces the warmer air at the ground level changing the wind to be breezy and denser.there is also an immediate drop in the temperature.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.

qualitative observation deals with data that can be observed with our senses: sight, smell, touch, taste, and hearing. they do not involve measurements or numbers. for instance, colors, shapes, and textures of objects are all qualitative observations.