Question

a block of copper (specific heat = 385 j/kg·k) requires 635,000 j of thermal energy to change in temperature from 17°c to 139°c. what mass of this copper block?
13.5 kg
5.68 kg
4.00 kg
11.9 kg
multiple choice 5 points
the of an object is a measure of the average kinetic energy of the particles in the object.
temperature
conductivity
charge

Explanation:

First Question (Mass of Copper Block)

Step1: Recall the heat formula

The formula for heat energy is \( Q = mc\Delta T \), where \( Q \) is heat energy, \( m \) is mass, \( c \) is specific heat, and \( \Delta T \) is the change in temperature.

Step2: Calculate the change in temperature

\( \Delta T = T_2 - T_1 = 139^\circ C - 17^\circ C = 122^\circ C \) (since the change in Celsius is the same as the change in Kelvin).

Step3: Rearrange the formula to solve for mass

From \( Q = mc\Delta T \), we get \( m = \frac{Q}{c\Delta T} \).

Step4: Substitute the values

Given \( Q = 635000 \, J \), \( c = 385 \, J/kg\cdot K \), and \( \Delta T = 122 \, K \) (or \( ^\circ C \)), substitute into the formula:
\( m = \frac{635000}{385 \times 122} \)
First, calculate the denominator: \( 385 \times 122 = 385 \times (120 + 2) = 385 \times 120 + 385 \times 2 = 46200 + 770 = 46970 \)
Then, \( m = \frac{635000}{46970} \approx 13.5 \, kg \)? Wait, no, wait, let's recalculate:
Wait, \( 385 \times 122 = 385 \times 122 \). Let's do 385120=46200, 3852=770, so 46200+770=46970. Then 635000 / 46970 ≈ 13.5? Wait, but let's check again. Wait, maybe I made a mistake. Wait, 385122: 122300=36600, 12285=10370, so 36600+10370=46970. Then 635000 divided by 46970: 635000 ÷ 46970 ≈ 13.5? Wait, but let's check the options. Wait, maybe I miscalculated. Wait, 385122=46970. 635000 / 46970 ≈ 13.5? Wait, but let's check the options. The first option is 13.5 kg. Wait, but let's check again. Wait, maybe I made a mistake in the change in temperature. Wait, 139 - 17 is 122, that's correct. Specific heat is 385 J/kg·K. So 635000 / (385*122) = 635000 / 46970 ≈ 13.5. So the mass is approximately 13.5 kg.

Second Question (Measure of Average Kinetic Energy)

The temperature of an object is defined as a measure of the average kinetic energy of the particles in the object. Conductivity is related to heat transfer, and charge is related to electric properties, so they do not measure average kinetic energy.

Answer:

(First Question):
13.5 kg (the first option)