Mrs. Lawrence's Thermochemistry Quiz

1. If a reaction releases heat (energy), it is referred to as

Endothermic

Exothermic

Isothermic

A chemical change

If a reaction releases heat (energy), it is referred to as exothermic. This means that during the reaction, energy is being released from the system into the surroundings. The reaction is characterized by a decrease in the internal energy of the system, resulting in an increase in temperature of the surroundings. This energy release can often be observed as an increase in temperature, production of light, or formation of a flame.

Explanation

If a reaction releases heat (energy), it is referred to as exothermic. This means that during the reaction, energy is being released from the system into the surroundings. The reaction is characterized by a decrease in the internal energy of the system, resulting in an increase in temperature of the surroundings. This energy release can often be observed as an increase in temperature, production of light, or formation of a flame.

2. To convert degrees Celsius to degrees Kelvin, you

Multiply by 1.8 and add 32.

Subtract 32 and divide by 1.8.

Add 273.

Subtract 273.

To convert degrees Celsius to degrees Kelvin, you need to add 273. This is because the Kelvin scale starts at absolute zero, which is -273 degrees Celsius. Adding 273 to the Celsius temperature will give you the equivalent temperature in Kelvin.

Explanation

To convert degrees Celsius to degrees Kelvin, you need to add 273. This is because the Kelvin scale starts at absolute zero, which is -273 degrees Celsius. Adding 273 to the Celsius temperature will give you the equivalent temperature in Kelvin.

3. Which of the following is NOT a unit for heat?

Celsius

Calories

Joules

Kilocalories

Celsius is a unit for temperature, not heat. Heat is measured in units such as calories, joules, and kilocalories. Celsius is used to measure the temperature of a substance or the amount of heat energy it contains, but it is not a unit for heat itself.

Explanation

Celsius is a unit for temperature, not heat. Heat is measured in units such as calories, joules, and kilocalories. Celsius is used to measure the temperature of a substance or the amount of heat energy it contains, but it is not a unit for heat itself.

4. The heat absorbed by 50g of water to change from 10C to 30C is equal to

50 calories

500 calories

1000 calories

1000 joules

The heat absorbed by a substance can be calculated using the formula Q = mcΔT, where Q is the heat absorbed, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature. In this case, the mass of water is given as 50g and the change in temperature is 30C - 10C = 20C. The specific heat capacity of water is approximately 1 calorie/g°C. Plugging in these values into the formula, we get Q = (50g)(1 calorie/g°C)(20C) = 1000 calories. Therefore, the correct answer is 1000 calories.

Explanation

The heat absorbed by a substance can be calculated using the formula Q = mcΔT, where Q is the heat absorbed, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature. In this case, the mass of water is given as 50g and the change in temperature is 30C - 10C = 20C. The specific heat capacity of water is approximately 1 calorie/g°C. Plugging in these values into the formula, we get Q = (50g)(1 calorie/g°C)(20C) = 1000 calories. Therefore, the correct answer is 1000 calories.

5. The heat required to melt 1 gram of a solid at its melting point is called the

Specific heat capacity

Heat of vaporization

Law of Conservation of Energy

Heat of fusion

The heat required to melt 1 gram of a solid at its melting point is called the heat of fusion. This term specifically refers to the amount of energy needed to change a substance from a solid to a liquid state, without changing its temperature. It is a measure of the strength of the bonds between the particles in the solid, as breaking these bonds requires energy. The heat of fusion is an important property to consider in processes such as melting or freezing substances.

Explanation

The heat required to melt 1 gram of a solid at its melting point is called the heat of fusion. This term specifically refers to the amount of energy needed to change a substance from a solid to a liquid state, without changing its temperature. It is a measure of the strength of the bonds between the particles in the solid, as breaking these bonds requires energy. The heat of fusion is an important property to consider in processes such as melting or freezing substances.