Question

PHYS 205 Winter 2019 Lab 1 Homework NAME 4. Suppose we heat sample A, which is 150 g of ice at-10 C, and sample B, which is 150 gofice at 0 °C, in the same microwave oven until both samples of water are at 30 °C. Will the time taken to heat sample A be (a) longer than, (b) shorter than, or (c) equal to the time to heat sample B? Explain your reasoning. 5. An ice cube at a temperature of-20 °C is put in a plastic bowl and which is in a microwave oven, and the oven is turned on. When the oven is turned off, the bow contains water that is at a temperature of 60 C. Assuming the microwave transferred energy to the ice at a constant rate throughout, draw a graph (below) of the temperature of the Ha0 as a function of time. The endpoints of the graph are given. n placed Finish: Water, 60-c time (s) Start: Ice, -20 °C Explain your graph looks the way it does. why

Answer 1

Sample �A� longer time than sample because �A� required energy to become -20 degree c, so it takes extra time to reach at 30 degree c, (since they have mass) therefore since dQ/dt = constant, therefore more heat is required more time taken. (i) -20 degree to 0 degree c () rightdoublearrow Q_1 = m s increment T = m(0.5) (20) Q_1 = 10 m (ii) 0 degree c (Ice) to 0 degree c (water) Q_2 = mL_mt = 80 m for melting (iii) 0 degree c (water) to 60 degree c (water) Q_3 = m s increment T therefore Q_3 = m(1) (60) = 60 m