__ 4. A beaker has 100 g of water.The amount of energy needed to raise the temperature of the water 5^circ C is approximately A 420J/gcdot ^circ C B 210J/gcdot ^circ C C. 2100J/gcdot ^circ C D 1000J/gcdot ^circ C

Here's how to solve this problem:<br /><br />1. **Understand the concept:** We need to use the specific heat capacity of water, which tells us how much energy is needed to raise the temperature of 1 gram of water by 1 degree Celsius. The specific heat capacity of water is approximately 4.2 J/g°C. This means it takes 4.2 Joules of energy to raise the temperature of 1 gram of water by 1 degree Celsius.<br /><br />2. **Apply the formula:** The formula for calculating heat energy (Q) is:<br /><br /> Q = m * c * ΔT<br /><br /> Where:<br /> * Q = heat energy (Joules)<br /> * m = mass (grams)<br /> * c = specific heat capacity (J/g°C)<br /> * ΔT = change in temperature (°C)<br /><br />3. **Plug in the values:**<br /><br /> * m = 100 g<br /> * c = 4.2 J/g°C<br /> * ΔT = 5°C<br /><br /> Q = 100 g * 4.2 J/g°C * 5°C<br /> Q = 2100 J<br /><br />4. **Answer:** The amount of energy needed is 2100 J. Therefore, the closest answer is **B**. Note that the question seems to have mixed up the units in the options. The correct unit for energy is Joules (J), not J/g°C. The question likely intends to ask for the total energy, which is 2100 J.<br />