Specific heat is a measure of how much heat energy must be added to one gram of a substance to cause a one degree Celsius increase in temperature. The formula for this relationship is:
Q= c*m* AT
• Q is the amount of heat added to the substance;
• c is the specific heat of the substance;
• m is the mass of the substance; and
• AT is the change in temperature of the substance.
A substance has a mass of 10 grams. This substance has 45 joules of heat added to it, and the change in temperature is 5 degrees. What is the specific heat of the substance? J/gK
Correct Answer & Rationale
Correct Answer: 0.9
To determine the specific heat, we use the formula \( c = \frac{Q}{m \Delta T} \), where \( Q \) is the heat added (45 J), \( m \) is the mass (10 g), and \( \Delta T \) is the temperature change (5 °C). Plugging in the values: \( c = \frac{45 \, \text{J}}{10 \, \text{g} \times 5 \, \text{°C}} = 0.9 \, \text{J/g°C} \). Other options may arise from calculation errors, such as misapplying the formula or using incorrect units. For instance, if one mistakenly divides by a different temperature change or mass, it would yield incorrect specific heat values. Thus, 0.9 J/gK accurately reflects the relationship between heat, mass, and temperature change for this substance.
To determine the specific heat, we use the formula \( c = \frac{Q}{m \Delta T} \), where \( Q \) is the heat added (45 J), \( m \) is the mass (10 g), and \( \Delta T \) is the temperature change (5 °C). Plugging in the values: \( c = \frac{45 \, \text{J}}{10 \, \text{g} \times 5 \, \text{°C}} = 0.9 \, \text{J/g°C} \). Other options may arise from calculation errors, such as misapplying the formula or using incorrect units. For instance, if one mistakenly divides by a different temperature change or mass, it would yield incorrect specific heat values. Thus, 0.9 J/gK accurately reflects the relationship between heat, mass, and temperature change for this substance.
Other Related Questions
If these results correctly predict the performance of this kneepad design, what is the probability that one of the kneepads will require a force of 145 N or greater to cause failure?
- A. 53%
- B. 22%
- C. 75%
- D. 25%
Correct Answer & Rationale
Correct Answer: D
To determine the probability of a kneepad requiring a force of 145 N or greater to cause failure, we analyze the data provided. The correct option, 25%, indicates that one-fourth of the kneepads are expected to fail under this force, aligning with statistical predictions for this design. Option A (53%) overestimates the likelihood, suggesting more than half will fail, which is not supported by the data. Option B (22%) underestimates the probability, indicating fewer kneepads will fail than expected. Option C (75%) is excessively high, implying a significant majority would fail, which contradicts the predicted performance. Thus, 25% accurately reflects the failure rate at this force threshold.
To determine the probability of a kneepad requiring a force of 145 N or greater to cause failure, we analyze the data provided. The correct option, 25%, indicates that one-fourth of the kneepads are expected to fail under this force, aligning with statistical predictions for this design. Option A (53%) overestimates the likelihood, suggesting more than half will fail, which is not supported by the data. Option B (22%) underestimates the probability, indicating fewer kneepads will fail than expected. Option C (75%) is excessively high, implying a significant majority would fail, which contradicts the predicted performance. Thus, 25% accurately reflects the failure rate at this force threshold.
Which statement describes one feature of the Rutherford-Bohr atom model that the Thomson model does not share?
- A. The Rutherford-Bohr model identifies different elements by the numbers of particles present.
- B. The Rutherford-Bohr model maintains the observed neutral charge of atoms.
- C. The Rutherford-Bohr model correctly describes the types of particles in the atom.
- D. The Rutherford-Bohr model restricts the positive charge of the atom to the nucleus.
Correct Answer & Rationale
Correct Answer: D
The Rutherford-Bohr model uniquely restricts the atom's positive charge to the nucleus, a significant advancement over the Thomson model, which depicts a diffuse positive charge throughout the atom. Option A is incorrect as both models can identify elements based on particle numbers, but the Rutherford-Bohr model adds more detail about electron arrangements. Option B is misleading; both models account for atomic neutrality, but the Rutherford-Bohr model provides a clearer structure. Option C is also inaccurate; while the Rutherford-Bohr model describes particles more accurately, it does not fundamentally change the types of particles present compared to Thomson's model.
The Rutherford-Bohr model uniquely restricts the atom's positive charge to the nucleus, a significant advancement over the Thomson model, which depicts a diffuse positive charge throughout the atom. Option A is incorrect as both models can identify elements based on particle numbers, but the Rutherford-Bohr model adds more detail about electron arrangements. Option B is misleading; both models account for atomic neutrality, but the Rutherford-Bohr model provides a clearer structure. Option C is also inaccurate; while the Rutherford-Bohr model describes particles more accurately, it does not fundamentally change the types of particles present compared to Thomson's model.
What statement describes one or more needed changes to this experiment that would allow the experimenter to draw a valid conclusion?
- A. Salt water should have been used to make the ice cubes for the cup of salt water.
- B. The time for ice cubes to melt should have been measured in minutes.
- C. At the beginning, both cups should have contained the same mass of water at the same temperature.
- D. The energy released should have been measured, not calculated.
Correct Answer & Rationale
Correct Answer: C
Option C highlights the necessity for both cups to start with the same mass of water at the same temperature to ensure a fair comparison. This control eliminates variables that could skew results, allowing for a valid conclusion about the melting rates of ice cubes in different solutions. Option A is incorrect because using salt water to make ice cubes would not provide relevant data on how the ice behaves in fresh versus salt water. Option B is not a change that affects the experimental validity; measuring time in minutes is appropriate, but the key is ensuring conditions are equal. Option D suggests a measurement method change, but calculating energy based on temperature changes is acceptable in this context.
Option C highlights the necessity for both cups to start with the same mass of water at the same temperature to ensure a fair comparison. This control eliminates variables that could skew results, allowing for a valid conclusion about the melting rates of ice cubes in different solutions. Option A is incorrect because using salt water to make ice cubes would not provide relevant data on how the ice behaves in fresh versus salt water. Option B is not a change that affects the experimental validity; measuring time in minutes is appropriate, but the key is ensuring conditions are equal. Option D suggests a measurement method change, but calculating energy based on temperature changes is acceptable in this context.
Which statement is a valid conclusion from the data?
- A. The male athletes used more energy than the female athletes after 30 minutes of exercise.
- B. Strenuous exercise is more difficult for male athletes than female athletes.
- C. The average increase in heart rate was lower for the females than for the males.
- D. All the females had a lower heart rate than the males after 30 minutes of exercise.
Correct Answer & Rationale
Correct Answer: C
Option C accurately reflects the data, indicating a measurable difference in heart rate between male and female athletes after 30 minutes of exercise. This conclusion is supported by the data trends, which typically show a higher average heart rate in males. Option A makes an assumption about energy expenditure without specific data to support it, making it invalid. Option B incorrectly suggests a subjective comparison of difficulty, which cannot be deduced from heart rate data alone. Lastly, Option D overgeneralizes by claiming that all females had lower heart rates than males, which is unlikely and not supported by typical statistical findings, as individual variations exist.
Option C accurately reflects the data, indicating a measurable difference in heart rate between male and female athletes after 30 minutes of exercise. This conclusion is supported by the data trends, which typically show a higher average heart rate in males. Option A makes an assumption about energy expenditure without specific data to support it, making it invalid. Option B incorrectly suggests a subjective comparison of difficulty, which cannot be deduced from heart rate data alone. Lastly, Option D overgeneralizes by claiming that all females had lower heart rates than males, which is unlikely and not supported by typical statistical findings, as individual variations exist.