GreekMan

We just began looking at uniform electric fields at school and for the weekend we were given some problems to complete. I came to one of the problems which involved a concept i am unsure about and so have had trouble completing the problem. I am a unsure of what it means when something has been earthed, so would somebody be able to help me with the following problem, and also if possible, expalin to me what it means when somethng has been earthed: What would the potential difference be between two parallel plates if the upper plate is at a potential of 1000V and the lower plate is earthed?

Which would transfer heat to water more efficiently, a glass beaker or an aluminium can?

We did do a practical on the enthalpy of combustion of certain hydrocarbons. During the lesson i commented on how the values that we calculated from the method that we used would not take into account the heat loss during the practical. However, that was the only practical we will be doing before we have to design this one. So i a really not sure what method to use in order to reduce the heat loss, or how to take into account the heat that is lost during the practical. Would someone be able to explain this to me?

For Chemistry we need to design and perform a practicle to determine the enthalpy of combustion of oly foods. We hve been told that the oily food we will be using is a variety of nuts. We have only just begun learning about enthalpy in Chemistry, and so I am not sure how I to design a method in order to determine the entahlpy of combustion of a nut. Would anybody be able to offer any assistance?