Physical heat energy answers

The physics interest group of 26 (08 Qinzhou) explored the ability of water on the earth's surface to absorb solar energy and conducted the following experiment: The basin is equipped with a surface area of ??6 kilograms of water, and the water is 0.1 square meters, when the sun shines After being lowered vertically for 15 minutes, the temperature increased by 5°C. Ask:

(1) How much energy did the water absorb within 6 kilograms of water in 15 minutes?

(2) How much heat does 1 square meter of water absorb per minute on average?

(3) If heated by the same mass as water with an elevated temperature, the liquefied gas burns in at least how many meters 3 way? (Assuming that all the heat released by burning LPG is absorbed by water, the calorific value of LPG is 5.0×107J/m3)

26. Answer:

(1) Q = cm △T = 4.2 × 10 Joules/(kg·℃) × 6 kg × 5 = ℃ × 1.26 10 Joules of heat

(2) On average, 1 square meter of water is absorbed per minute:

Q = = = 8.4×10J/min·m BR> (3) Obtained from Q = VQ: V = = = 2.52×10 m

24 (08 Tianjin) (5 points) It is known that the specific heat capacity of aluminum is 0.88×103J/(kg·℃). It represents the mass absorption when the heat in liters of kilograms of aluminum block at temperature I°C is absorbed. According to the physical meaning of the specific heat capacity mentioned above. Please calculate: the mass of a 5 kg aluminum block heated to 100°C at a temperature of 20°C. Heat absorbed by the number of aluminum blocks

Answer: 0.88×10J

Q = cm (TT) = 0.88×10J/(kg·℃)×5kg×(100℃-20 ℃)

= 3.52×10J

38 (08 Beijing) built a thermos of water. The temperature of 1kg water dropped from 90℃ to 40℃. The specific heat of water is called 4. What is the water heating requirement within 2×103J/(kg℃)? What is the discharge hot water bottle?

The answer; 2.1×105J

Page 2 (08 Miyun, Beijing) With a 3 kg thermos bottle with a built-in water temperature of 95°C to 45°C, how much heat does the water in the thermos bottle release?

(08 Qingdao) Heating 500 grams of water to 80℃, 4.2×104J absorbs heat, the water temperature is ℃, and the water temperature is the original ℃.

Answer: 20; 60.

17 (08 Huangshi) After a solar water heater is filled with water, the water quality is 30 kilograms. To raise the temperature of water from 20°C to 70°C it is necessary to absorb heat. If the heat is provided by the combustion of natural gas, at least incomplete combustion of natural gas cubic meters. (C water = 4.2 × 103J / (kg·℃ 8 liters × A 107J/cubic meter solar water heater is filled with 40 kilograms of water. Under sunlight, the water temperature is 25°C (calorific value of natural gas)

25 (08 Kunming) (6 points), find: (1 ) Water absorbs heat; (2) The exact amount of heat equivalent to the release of kilograms of coke is thermal burning [: q coke = 3×107J/kg angle water = 4.2×103J/(kg·℃)]

46 (08 Panzhihua) Solar energy is a clean energy source. The solar water heater can increase the temperature of water by 30°C per day by 500 kilograms, and then the heat released by the water is equivalent to the heat absorbed by burning a complete cubic meter of gas (J). The calorific value of natural gas is 7×107J/cubic meter, and the specific heat capacity of phosphorus water = 4.2×103J/(kg·℃))

29. (10 points) Measure water with a thermometer containing 2g of mercury Beaker

Temperature Tiger, 14

(1) Please use a thermometer to indicate the existence of two problems:

①;

(2) The thermometer displays the mass, volume, and density of mercury during the rising process (the words "rising", "decreasing" or "unchanged")

(3) The thermometer shows the amount of increase in the internal energy of mercury during the process (the word "increase" or "decrease") which is produced by the tract (the word "agent" or "heat transfer") can be changed in leaving.

(4) If the quantity displayed by the thermometer increases by 20°C, then how much heat is absorbed by mercury? The specific heat capacity of mercury is known to be C = 0.14 × 103 Joule/(kg· ℃)

Answer;?

(1) The line between the line of sight of the glass bulb thermometer in contact with the container (point 1) and the reading of the thermometer is not flush with the bottom of the surface (point 1)

( 2) Unchanged (1 point) Increased (1 point) Decreased (1 point) (3) Increased (1 point) Heat transfer (1 point)

(4) Heat absorbed by mercury Q = = cm⊿t0.14×103J/(kg·℃)×2×10-3kg×20=℃

5.6J Page 2 (08 Anhui) As shown in the figure, by using Beijing 2008 The Olympic torch bearer fuel is propane. Propane is liquefied in a gaseous state at room temperature through storage and transportation in a small propane tank under pressure. If the calorific value is 8.0×107J/kg, a 450g propane tank can be equipped with a complete combustion heat release temperature _______J

Answer: 3.6x107

24 (08 Taiyuan) The following table shows the technical parameters of some cars of a certain brand, in which the displacement means the working volume of the engine cylinder. Under normal circumstances, the engine Displacement, more power. Air-fuel ratio refers to the mass of air and fuel in the cylinder. The calorific value of gasoline means that the heat released by complete combustion per kilogram of gasoline is 4.6×103J. When the engine is at maximum power, the mixed cylinder gasoline and air density are 1.35 kg/m3, and the high-temperature and high-pressure gas pushes the piston 2,600 times in 1 minute. Please calculate (1) within 01 minutes

The engine does useless work when operating at maximum power.

(2) It affects the consumption quality of gasoline.

(3) In engine efficiency.

Solution: (1) 1 minute of useless work: W = PT = 75×10 width×60 = 4.5×10 Joules

(2) Work must be done with high-quality gasoline Consumption:

M = =ρV1.35kg/m×1.8 x10m×1.62 =×10kg

(3) The heat energy released by complete combustion of gasoline within 1 minute:

Q = 1.62×10kg×4.6×10J /catties×2600 = 1.94×10J

Engine efficiency:

η=×100%=×100% = 23.2%

(08 Wuhu) One hundred thousand plastic bags are used to make barrels of crude oil in China’s annual consumption. It is known that the calorific value of oil is 4.4×107 Joules/kg, and the heat that can be released after complete combustion of L kg is ______J. If only 42% is absorbed in water, at room temperature, the temperature of the water can rise ______kg 2 0℃[ Water 4.2×103 Joules/specific heat capacity (kg·℃)]. Since June 1, 2008, China has begun to restrict the use of plastic bags for the purpose of______(write can).

Answer: 1.4x107; 220; Energy (reducing pollution, protecting the environment) protection;

12 (08 Jiangmen) The volume specific heat capacity of water is called 4.2×103 Joules/(kg ·℃), L kg, water at 20℃ absorbs 2.1×105J of heat, and the temperature rises to ℃. In life, we often see car engines driving tank irrigation. This is because the water is large, so more water can be taken under the same conditions, and the heat dissipation effect is good.

Answer: 70; specific heat capacity; heat.

35. (08 Hangzhou) In the experiment, when the water temperature rose to 89℃ for "boiling water observation", Xu started the time and recorded the water temperature for 1 minute each time. Then, plot the temperature versus time image based on the experimental data.

(1) As can be seen from the image, the beginning of the time required for water to heat from 93°C to boiling is ▲ minutes.

(2) It can be inferred from the image that if the water continues to be heated for 1 minute, the temperature of the water remains unchanged under other conditions and is ▲℃.

(3) If the mass of the experimental water allowed to be measured is LKG, the water will be heated from 89°C to 94°C to the amount of heat absorbed [C specific heat of water = 4.2×l03J/(kg ·℃)

Answer:? 35. (6 points)

(1)3; (2 points)

(2)99 (2 points)

(3) According to △T (1 minute) you can get: Q = 4.2×103×1×5 = 2.1×104 (J Q = cm) (1 minute)

35. (08 Nanjing) Use a gas stove to boil water, gas 0.5 kg, making 50 kg of water increase from 20℃ to 70℃. The specific heat capacity of water is called 4.2×103J/(kg·℃), and that of hot gas is 4.2×107J/kg. Requirements:

(1) Heat release from incomplete combustion of 0.5 kg of gas.

(2) Water (3) Water heater, gas stove efficiency

Answer: Heat absorbed:

(1) Heat released by 0.5 kg of completely burned gas

Q = MQ =0.5 kg × 4.2 × 10J / kg = 2.1 × 10J

(2) Water absorption heat

Q = cm (TT) = 4.2 × 10J / (kg·℃ ） %=×100%=50%

31 (08 units) (6 points) Xiaoxing household solar hot water heater with a water tank capacity of 200L. Xiaoxing conducted observation activities: one morning, he used a thermometer to measure the water temperature at 20°C, and then sent the water heater to the water tank. At noon, the "temperature sensor" showed that the water tank temperature was 45°C. Please solve the following problems:

(1) The mass in the water tank; the water heat absorbed by the water and [c = 4.2×103J/(kg·℃)] (4 points)

(2) If water absorbs heat provided by burning gas, a gas stove and an efficiency of 40%, at least ask how much gas is burned (calorific value of gas q = 4.2×107J/kg) (2 points) (2) Water absorbs heat. (3) Water boiling efficiency of gas stove.

//Pure thermal calculation!

24. (08 Guang'an) 1 kg of coal can release 2.9×107J of heat and can heat 20 kg of water to 100℃[C water = 4.2×103J/complete combustion (kg·℃)].

36 (08 Wuxi) At the beginning of this year, the freezing snow in southern China affected the hearts of people across the country.

(1) Snow and ice cover cause damage. If the weight of the wire somewhere between two adjacent poles is 3000N, when the volume of snow-covered ice reaches 10 cubic meters of filaments, will the gravity of these ice filaments themselves be many times greater? (G is taken as 10N/kg, ice ρ = 0.9×103 kg/cubic meter)

(2) Snowstorms cause tensions in countries with a wide range of power. In severe cases, if the meter is pressed for one day and the power shortage is 3.4×1015J, how many tons of coal energy is equivalent to the energy produced by incomplete combustion? (Q = Coal 3.4×107J/kg)

(3) Xiao Ming said on TV that in order to make the roads blocked by ice and snow open as soon as possible, people in some places spread salt on the icy roads. Xiao Ming guessed that the reason may be that it shortened the melting time with the salt ice. Is this guess correct? Xiao Ming decided to use the refrigerator at home to make ice and explore it in a room with a room temperature of about 10°C. Xiao Ming helps you design a feasible option.

//Hot comprehensive, comprehensive power hot topic!

15 (08 Yancheng) The chemical energy converted into energy by burning wheat straw has a very low utilization rate. To solve this problem, a research team dried rice straw at a pressure of 1.2×106Pa and made coal from the straw. The physical meaning of 1.2×106Pa is the pressure of n forces per square meter of area; the calorific value of coal straw is 2.2×107J/kg. The complete combustion of 1kg of straw coal can release heat.

0 (08 Chongqing) Car radiators and other refrigeration equipment commonly use water as a coolant, which is the greater ______________________ property of water used; if the car radiator is installed in water 5KG, the temperature is 10 process At ℃, heat is absorbed by water____________________J. [Known C in water = 4.2×103J/(kg·℃)]

29 (08 Suzhou) is equipped with a solar water heater with 100KG of cold water at 20°C. After one day, the water temperature rises to 60°C. These absorption Calories of water J. These calories are equivalent to the heat given off by kilograms of completely burned gases.

[4.2×103J/(kg·℃) specific heat capacity of water, hot gas is 4.2×107J/kg]

Answer: (1) 1.68×107 (2) 0 0.4

53 (08 Harbin) (6 points) Use the materials processing equipment at the construction site as shown in the figure. The efficiency of the known diesel engine is 40%, the calorific value of diesel is 4×107J/kg, when the device is upgraded to 3200N by 5m of reconstructed material. Lasting 4 seconds, 4 grams of diesel fuel

The incomplete combustion of 4 grams consumed by the diesel engine (1) releases a large amount of heat? What is the engine output?

(2) How much wasted work is done by the building materials of the reinforcement? What is the efficiency of the entire device?

(3) Please use the website to evaluate the rationality of the unit’s construction.

20 (08 Zhenjiang) has the advantages of hydrogen, high calorific value, no pollution and many other advantages. The thermal hydrogen value is 14.3×107J/kg, and the combustion of 0.5 kg of hydrogen can completely release heat; if half a tank of hydrogen is spent, the calorific value of the remaining hydrogen (greater than/equal to/less than) is 14 0.3×107J/kg.

Answer: 7.15x107; equal to

28 (08 Zhenjiang) (7 points) Determine the rated power efficiency of the student's physics interest group electric water heater kilowatt water heater add 2 kg of water so the water heater Work, and draw a graph of the temperature changes with time during electrical heating treatment, find:

(1) After heating for 2 minutes, the temperature of the water will rise a lot. C?

(2) How much heat does the water absorb when heated for 6 minutes?

(3) The efficiency of the electric water heater refers to the ratio of water to absorb heat and the heat released by the electric water heater. How normal is the efficiency of the water heater?

21 (08 Foshan) Xiaotong’s family used bottled liquefied petroleum gas, and the liquefied petroleum gas bottle was charged with a weight of 21 kilograms. LPG takes a calorific value of 5×107J/kg.

(1) How much heat is released when 1 kilogram of LPG is completely burned?

(2) If the heat of complete combustion of 60% LPG bottle is released, then the heat is dissipated?

(3) Xiaotong wants to save energy and reduce energy consumption. How much heat can you put in water at 20℃ to be heated to 100℃ for all the heat lost during use?

15 (2008 Bengbu II) Xiao Ming, who lives on the fifth floor of a seven-story dormitory building, installed electric-assisted solar water heaters on the roof of each floor of his house, receiving 50% of the total effective area of ??solar energy. , which can receive the internal energy of water converted from solar energy. Requirements: ⑴ Assuming the height of the water pipes in Xiaoming's home from the mouth to the seven roof surfaces from the small household water pressure ground to the height of the water heater tank next to the roof of the fifth-floor tank, how many should be at least acted upon? ⑵

When the weather is fine, if the average solar radiation per square meter of area is obtained in one hour, this food can be heated to what mass of water can be heated every day when the initial temperature is 20°C Spend? (Receiving daily solar energy for 10 hours, the specific heat capacity of water is ℃).

Answer; (1) W = MGH = 9000J (4 points)

(2) Q =cmΔt=4.2ⅹ103100 (T-20)=2.8ⅹ106 1.2 10 50% , T = 60℃..