[填空题]
In an experiment, a liquid-filled beaker is positioned on an elecc7 7fqtp k4r v,b1j3vqt7nc lyn uiz-5 lme0kql3;;sa:ronic balance. An immersion heat75a3-uen;lq cs:kmiy ;zn0 ller with a power rating of$P$ is introduced into the water. Once the water begins to boil, a researcher monitored the change in mass $m$ of the liquid over time $t$ once the boiling commenced.
The theoretically predicted relationship between time $t$ and $m$ ism$L_v=\frac{Pt}{C-m}$
C is the initial mass of the liquid when t=0s and$L_v$ is the latent heat of vaporisation of water.
1.Give the units of $L_v$ in fundamental SI units.
2.In a particular experiment, the researcher uses a heater of power 65.0$\pm$0.1W and measures m=0.120$\pm$0.001kg,C=0.125$\pm$0.001kg,and t=600$\pm$1s.
1.Calculate the percentage error in the measured value of $L_v$. %
2.For this experiment, calculate the value of $L_v$ and its absolute uncertainty. $\times10^6J\:kg^{-1}$
3.The accepted value of $L_v$ is $2.3\times10^6J\:kg^{-1}$.Explain why the experimental value does not match the accepted value.
3.The researcher plots a graph to show how m varies with t.
1.Outline why P must be kept constant during the experiment.
2.Assuming the relationship $L_v=\frac{Pt}{C-m}$ is correct, sketch the expected mass-time relationship on the axes below. (There is no need to put numbers to the axes).
3.Outline how to obtain the value of $L_v$ from the graph you have drawn in c(ii).
