[填空题]
In an experiment, a liquid-filled beaker is positioned k9 u* *dt4ybsorf w37i35e ribnhhy cj)g6es z*147 iion an electronic balance. An immersion heater 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 ofe j ih*h47nigc) s6y1z the liquid over time t once the boiling commenced.
The theoretically predicted relationship between time $t$ and $m$ is $L_v$=$frac{Pt}{C−m}$
$C$ is the initial mass of the liquid when $t=0\,s$ 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±0.1 W and measures m=0.120±0.001kg, C=0.125±0.001 kg, and t=600±1 s.
(1)Calculate the percentage error in the measured value of $L_v$. $The\,percentage\,error\,of\,L_v$
= %
(2)For this experiment, calculate the value of $L_v$ and its absolute uncertainty. $L_v$ = $\times10^6\,Jkg^{-1}$
(3)The accepted value of $L_v$ is $2.3\times10^6\,Jkg^{−1}$. 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).
