Chemistry B Unit Test 3
1. An ice pack makes the surroundings cold. This is an example of...
an endothermic reaction
an exothermic reaction
a system in equilibrium
a system that releases heat
2. Which of the following needs to remain constant in order for a calorimeter
to work effectively?
temperature
time
pressure
none of the above
3. Which of the following graphs shows an exothermic reaction? How do you know?
A because the ∆H value is positive
B because the ∆H value is negative
A because the ∆H value is negative
B because the ∆H value is positive
4. A 500g piece of Aluminum has a temperature increase of 7 degrees. The specific heat of Aluminum is 0.900 J/gC. If you were using q = m c ∆T to find the amount of heat produced, which value would you plug in for "m"?
500 g
0.900 J/gC
3150 J
7 degrees
5. What is a potential energy diagram used for?
To show how much kinetic energy is released in a chemical reaction
To show the change in potential energy of the reactants and the products of a reaction
To show the potential energy in the surroundings versus the system
To show the kinetic energy versus the potential energy of the reactants only
6. For the formula: q = m c ∆T, What does the c stand for?
heat
mass
specific heat
change in temperature
7. For the formula: q = m c ∆T, What does the ∆T stand for?
heat
mass
specific heat
change in temperature
8. Water has a relatively high specific heat capacity. This means that...
it takes a lot of heat energy to increase its temperature.
it is easier to heat up and does not take much energy to do so.
it does not change temperature.
it does not absorb heat energy very well.
9. The amount of energy that is required to raise the temperature of one gram of pure substance or material by one degree Celsius (1°C) is called __________.
enthalpy
specific heat
mass
temperature
10. Nitrogen reacts with hydrogen to produce ammonia according to the following equation: N2(g)+3H2(g)→2NH3(g); ΔH=-92 kJ mol-1 The energy change for this reaction is best described as...
exothermic, because the energy of the bonds in the products is greater than the energy of the bonds in the reactants
endothermic, because the energy of the bonds in the products is greater than the energy of the bonds in the reactants
exothermic, because the energy of the bonds in the products is less than the energy of the bonds in the reactants
endothermic, because the energy of the bonds in the products is less than the energy of the bonds in the reactants
11. According to the following chart that shows specific heat capacity values, which of the following substances would heat up the fastest?
Aluminum
Copper
Gold
Water
12. What is the name of the device that is used to measure the amount of heat absorbed or released during chemical reactions?
Heat tranfser
Heat of formation
Specific heat
Calorimeter
13. In which of the following scenarios would water molecules have the highest average kinetic energy?
Liquid water at 90 °C
Steam at 200 °C
Ice at 0 °C
Liquid water at 89 °C
14. If two objects have different temperatures, heat will flow from the warmer object to the cooler one UNTIL ____________
one object freezes
both objects increase in temperature
they both have the same temperature
one reaches a temperature of zero
15. For a skillet, used for cooking food, do you want a high or low specific heat? Why?
High, so that it will need more energy to heat up.
Low, so that it will change temperature quickly.
The type of skillet does not affect how fast it heats up.
Need more information to determine.
16. A metal cube at temperature of 10°C immersed in a liquid at temperature of 70°C. What is the temperature of the metal cube when thermal equilibrium is achieved between the cube and the liquid?
Same as the room temperature
Less than 10°C
Between 10°C and 70°C
More than 70°C
17. Heat energy moves from __________ to __________ objects.
cooler, warmer
small, large
large, small
warmer, cooler
18. Using q = m c ∆T, calculate the energy (q) released when 240 g of iron is cooled by 65 °C. The specific heat (c) of iron= 0.452 J/g°C
-7051.2 J
-15,600 J
-108.48 J
-29.38 J
19. Explain how calorimetry works. What is the process? How is the data used?
20. When thinking about flow of heat, describe what would happen if you submerged a scorching hot piece of iron metal in a bath of cool water. What happens to the water? What happens to the iron? Explain why.
21. In your own words, explain how having an understanding of the chemistry behind energy is useful when looking at the calories in different food items.
plz I need help my first time on this website.....
1. To answer question 1, we need to understand the concept of endothermic and exothermic reactions. An endothermic reaction is a reaction that absorbs heat from the surroundings, while an exothermic reaction is a reaction that releases heat into the surroundings. In this case, since an ice pack makes the surroundings cold, it is an example of an exothermic reaction, where the ice pack releases heat into the surroundings. Therefore, the correct answer is "an exothermic reaction".
2. For question 2, we need to determine which variable needs to remain constant for a calorimeter to work effectively. A calorimeter is a device used to measure the amount of heat absorbed or released during a chemical reaction. To obtain accurate results, the temperature inside the calorimeter needs to remain constant. Therefore, the correct answer is "temperature".
3. In question 3, we are asked to identify which graph represents an exothermic reaction. In an exothermic reaction, heat is released from the system into the surroundings. This means that the ∆H (change in enthalpy) value for the reaction will be negative. Looking at the answer choices, we can see that option B has a negative ∆H value. Therefore, the correct answer is "B because the ∆H value is negative".
4. Question 4 asks which value to plug in for "m" in the equation q = m c ∆T when calculating the amount of heat produced. Here, we are given a 500g piece of Aluminum, so the mass (m) would be 500 g. Therefore, the correct answer is "500 g".
5. A potential energy diagram is used to show the change in potential energy of the reactants and products of a chemical reaction. Therefore, the correct answer for question 5 is "To show the change in potential energy of the reactants and the products of a reaction".
6. In question 6, we need to determine what the "c" stands for in the equation q = m c ∆T. Here, "c" represents the specific heat of the substance, which is the amount of heat energy required to raise the temperature of one gram of the substance by one degree Celsius. Therefore, the correct answer is "specific heat".
7. Question 7 asks for the meaning of the symbol ∆T in the equation q = m c ∆T. In this equation, ∆T represents the change in temperature, calculated by subtracting the initial temperature from the final temperature. Therefore, the correct answer is "change in temperature".
8. Water having a relatively high specific heat capacity means that it takes a lot of heat energy to increase its temperature. This is because water has strong intermolecular forces, and it can absorb a large amount of heat energy before its temperature starts to rise significantly. Therefore, the correct answer for question 8 is "it takes a lot of heat energy to increase its temperature".
9. The amount of energy required to raise the temperature of one gram of a substance by one degree Celsius is called specific heat. Therefore, the correct answer to question 9 is "specific heat".
10. According to the given equation and the given value of ΔH, we can determine that the energy change for this reaction is exothermic. An exothermic reaction releases energy, and since the ΔH value is negative (-92 kJ mol^-1), it indicates a release of energy. Therefore, the correct answer for question 10 is "exothermic, because the energy of the bonds in the products is less than the energy of the bonds in the reactants".
11. To determine which substance would heat up the fastest, we need to consider the specific heat capacity values given in the chart. The substance with the lowest specific heat capacity will heat up faster because it requires less heat energy to raise its temperature. Looking at the options, we can see that aluminum has the lowest specific heat capacity value. Therefore, the correct answer for question 11 is "Aluminum".
12. The device used to measure the amount of heat absorbed or released during chemical reactions is called a calorimeter. Therefore, the correct answer to question 12 is "Calorimeter".
13. The average kinetic energy of water molecules is directly related to the temperature of the water. According to the kinetic molecular theory, as the temperature increases, the average kinetic energy of the molecules also increases. Therefore, the water molecules would have the highest average kinetic energy in scenario B, where the liquid water is at 90 °C. Therefore, the correct answer for question 13 is "Liquid water at 90 °C".
14. When two objects have different temperatures, heat will flow from the warmer object to the cooler one until they both reach the same temperature. Heat always flows from higher temperature to lower temperature until equilibrium is reached. Therefore, the correct answer for question 14 is "they both have the same temperature".
15. For a skillet used for cooking food, it is preferable to have a low specific heat. This is because a low specific heat means that the skillet can change temperature quickly when heat is applied, allowing for faster and more efficient cooking. Therefore, the correct answer for question 15 is "Low, so that it will change temperature quickly".
16. When thermal equilibrium is achieved between the metal cube and the liquid, they will both reach the same temperature. In this case, the temperature of the metal cube will be between 10°C and 70°C. Therefore, the correct answer for question 16 is "Between 10°C and 70°C".
17. Heat energy moves from warmer objects to cooler objects. This is because heat flows from higher temperature regions to lower temperature regions in order to equalize the temperature. Therefore, the correct answer for question 17 is "warmer, cooler".
18. To calculate the energy (q) released when cooling 240 g of iron by 65 °C, we can use the equation q = m c ΔT, where m is the mass, c is the specific heat, and ΔT is the change in temperature. Plugging in the known values, we get q = (240 g) × (0.452 J/g°C) × (65 °C) = -7051.2 J. Since the energy released is negative (indicating the release of heat), the correct answer for question 18 is "-7051.2 J".
19. Calorimetry is the process of using a calorimeter to measure the amount of heat absorbed or released during a chemical reaction. The process involves placing the reactants or products into a calorimeter, which is an insulated container. The reactants undergo the chemical reaction, and the heat transfer is measured by monitoring the temperature change inside the calorimeter. The data obtained from calorimetry can be used to calculate the heat of reaction, determine the specific heat of substances, and study energy changes in chemical processes.
20. When a scorching hot piece of iron is submerged in cool water, heat will flow from the iron (hotter object) to the water (cooler object). This is because heat moves from higher temperature regions to lower temperature regions. As a result, the water will absorb heat energy from the iron and its temperature will increase. The iron, in turn, will lose heat energy to the water and its temperature will decrease. Eventually, both the water and the iron will reach a thermal equilibrium, where their temperatures stabilize and become equal. This process occurs due to the transfer of heat energy through conduction and convection.
21. Having an understanding of the chemistry behind energy is useful when looking at the calories in different food items because it helps us understand how the energy stored in chemical bonds is released when food is digested. Different food items have different amounts of stored chemical energy, and by understanding the chemistry of metabolism and energy release, we can make informed choices about the types and quantities of food we consume. Additionally, understanding energy chemistry allows us to calculate the energy content of food items and make dietary choices based on our energy needs.
1. An ice pack making the surroundings cold is an example of an exothermic reaction.
2. Temperature needs to remain constant in order for a calorimeter to work effectively.
3. Graph B shows an exothermic reaction because the ∆H value is negative.
4. For "m" in the equation q = m c ∆T, you would plug in the value 500 g.
5. A potential energy diagram is used to show the change in potential energy of the reactants and products of a reaction.
6. In the formula q = m c ∆T, "c" stands for specific heat.
7. In the formula q = m c ∆T, "∆T" stands for change in temperature.
8. Water having a relatively high specific heat capacity means that it takes a lot of heat energy to increase its temperature.
9. The amount of energy required to raise the temperature of one gram of a substance by one degree Celsius is called specific heat.
10. The energy change for the reaction between nitrogen and hydrogen to produce ammonia is exothermic because the energy of the bonds in the products is less than the energy of the bonds in the reactants.
11. According to the specific heat capacity values, gold would heat up the fastest.
12. The device used to measure the amount of heat absorbed or released during chemical reactions is called a calorimeter.
13. Steam at 200 °C would have the highest average kinetic energy for water molecules.
14. Heat will flow from the warmer object to the cooler one until they both have the same temperature.
15. For a skillet used for cooking food, you want a high specific heat so that it will need more energy to heat up.
16. When thermal equilibrium is achieved between the metal cube and the liquid, the temperature of the metal cube will be between 10°C and 70°C.
17. Heat energy moves from warmer to cooler objects.
18. Using the formula q = m c ∆T, the energy released when 240 g of iron is cooled by 65 °C is -7051.2 J.
19. Calorimetry works by measuring the heat exchange between a system and its surroundings. This is done by using a calorimeter, a device that can isolate the system and measure temperature changes. The data collected from calorimetry can be used to calculate the heat capacity or specific heat of a substance, determine the energy change in a chemical reaction, and analyze the energy content of food.
20. When a scorching hot piece of iron metal is submerged in cool water, the water will heat up and the iron will cool down. This is because heat from the hot iron will transfer to the cooler water until thermal equilibrium is reached. The water will absorb the heat energy from the iron, causing its temperature to rise, while the iron will lose heat energy to the water, causing its temperature to decrease. This process is known as heat transfer or thermal conduction.
21. Having an understanding of the chemistry behind energy is useful when looking at the calories in different food items because the energy content of food is measured in calories. These calories represent the amount of energy released when the food is metabolized in the body. By understanding the chemistry of energy, we can analyze the nutritional content of food and make informed decisions about our diet and overall health.