2. Solar energy slightly promotes the water cycle.
3.C
4. Hydrogen and oxygen are obtained after water electrolysis, indicating that they are composed of hydrogen and oxygen.
5.400 grams
6.CBDEA remains 3. 1 times 10 to the third power.
7.C
8. 16.2 18 1.7
9. Increased pressure
10.A
1 1.C
12. A barrel with large contact area and low pressure 1.6 times 10 to the fifth power.
1 Measure the mass of 20 needles first, then measure the mass of this pile of needles, and divide it by 1 needle mass to get the number of needles in this pile.
2 measure the mass m, calculate G=MG, and measure the contact area s, P=G/2S=MG/2S.
two
1.A
2.B
3. 1288 times 10 cubic 1.5 times 10 cubic buoyancy has nothing to do with the immersion of the object.
4.A
5.600 N 200 kg /M2 44
6.0.8n0. 12kg omitted
7. Increase or decrease is equal to 2 10.5.
8.& lt is not 20%
9. Crystal precipitation lowers the temperature, and the solubility of potassium nitrate decreases; The sinking concentration, density and buoyancy of wood blocks decrease.
10. Saturated solution can be concentrated solution or dilute solution. Add NACI solid evaporation solvent 1 105 to the third solution (which cannot be pumped out). seven
1 1. 10。 8G 50G
three
1.D
2.B
3.C
4.A
5.A
6.D
7.D
8.D
9. Omit
10. Tension f, length of scale component l fl/v10-(P0-fl)/v p.
four
1. Take the air out of the packaging bag to prevent bacteria from entering. Because there is no air, the packaging bag is crushed by atmospheric pressure and sticks tightly to the food.
2. When the pressure decreases and the boiling point decreases, the temperature in the pot is still higher than 100 food intake.
3.D
4.B
5.D
6.A
7.A
8.D
9.B
10. High temperature in summer, low temperature in winter and little annual precipitation.
1 1. Specific heat is a characteristic of substances, and each substance has its own specific heat. The specific heat of water is the largest. Several different substances have the same specific heat, such as ice and kerosene.
12. Low north wind and high north wind are cold and dry.
five
1. During the day, the temperature of sand on the desert surface is high, and many animals have formed the adaptability of staying up at night in order to avoid initial burns.
2.D
3.B
4. neuron d
5. Yes, in order to avoid the improper influence of auxin produced by terminal buds, A should be selected as the research object. If auxin produced by leaves of C and A and B is selected, the third group cannot be established.
6. 123675 48 8
7. Effector of auditory afferent nervous system
six
1.C
2.B
3.
4.A
5.B
6.B
7.B
8.A
9.C
10.a is greater than diastolic increase, rising and increasing sweat evaporation C.
seven
1.S 1 When S2 is closed, L 1 and L2 are both open; S2 is off, while S 1 is on, L 1 and L2 are not lit; When both S 1 and S2 are closed, L 1 is open and L2 is closed.
2.A
3.A
4.D
5.B
6.A
7.A
8. 100 Euro
9. 16。 7 ou
eight
1.D
2.B
3.A
4.B
5.C
6.A
7.D
Step 8 omit