To determine whether the reaction was exothermic (gave off heat) or endothermic (absorbed heat).
Measuring it before, after and during the reaction with a thermometer.
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One reason is because certain reactions require a precise temperature to occur. If the temperature is not achieved and maintained precisely then the reaction will stop.
Yes. It existed before human beings did, or before the solar system.
Ignition temperature is the temperature a substance needs to reach before it is combustible. Activation energy is the energy required to start a reaction occurring. Temperature is directly affected by heat. Heat is a form of energy. Therefore as you add energy to a substance it heats up. It will reach its ignition temperature and combust. The combustion is the reaction.
The temperature will depend on the reaction that is under consideration.
Temperature.
As the temperature increases, the reaction time decreases.
An increase in temperature speeds up the reaction rate.
You measure the ambient temperature before the experiment in case the experiment is sensitive to ambient temperature. You want to record all of the environmental factors that might affect the experiment before starting it. You measure the ambient temperature after the experiment for the same reason, and also in case the experiment affected the ambient temperature. Depending on the experiment, environmental factors may need to be considered when analyzing the results.
You measure the ambient temperature before the experiment in case the experiment is sensitive to ambient temperature. You want to record all of the environmental factors that might affect the experiment before starting it. You measure the ambient temperature after the experiment for the same reason, and also in case the experiment affected the ambient temperature. Depending on the experiment, environmental factors may need to be considered when analyzing the results.
Temperature xD