First year science questions

This one is so simple, I've done it.

1) Hypothesis: Is it the stirring of saliva with the tongue and the chewing of the teeth that sweetens the steamed bread and rice?

2) Requirements:

1.Grated steamed buns or rice.

2.Whole pieces of steamed bread or rice (use these to simulate the action of teeth respectively) 3Stirring of the tongue.

4.Saliva. Experimental Plan:

Group experiment 1: 1+3+4 (numbers are conditional serial numbers) and group experiment 2: 2+3+4

Group Experiment 3: 1+4

Group Experiment 4: 2+4

Group Experiment 5: 1+3

Group Experiment 6: 2+3

Description: Experiments 1 and 2 are the comparison of ground or unground steamed bread with iodization after tongue agitation and saliva.

Experiments 3 and 4 are the result of iodization without the action of the tongue.

Experiments 5 and 6 are the result of iodization without saliva.

1.Turn blue 2No blue.

The case of blueing is that the starch has not changed.

It does not change blue because the starch is broken down by salivary amylase into maltose.

Then through experiments, we know that experiment 1 is equivalent to people eating steamed bread, and the changes of steamed bread in the oral cavity.

The steamed bread is ground by the action of the teeth, and in the saliva, it is stirred evenly by the tongue to further decompose the starch in the saliva.

Starch is broken down by salivary amylase in the mouth to form sugars.

Plate tectonics, six large, "floating", asthenosphere, easy to trigger, Eurasian plate, American plate, African plate, Pacific plate, Indian Ocean plate, Antarctic plate, stable, active, non-stop, internal, external, wind, flowing water, glacier, wave, different, same, variable, steep slope, gentle slope, cliff, valley, ridge, saddle,

Plate drift six major gradually undercurrents more in Asia and Europe Africa Antarctica.

If you want to know more. Secret chat.

6.【Experiment 1】Fill the gas collection cylinder with a small amount of water in advance, and divide the remaining volume into five equal parts, and mark it. Then fill the burning spoon with a rubber stopper and a conduit with a sufficient amount of red phosphorus, clamp the latex tube with a spring clamp, ignite the red phosphorus in the combustion spoon, and immediately go deep into the gas collection cylinder to plug the rubber stopper.

After the red phosphorus is extinguished and the experimental device has cooled to room temperature, open the spring clamp.

1) Is it possible to conduct experiments with charcoal?

No, reason: The product is a gas

2) The phenomenon seen in the experiment is that a large amount of white smoke is produced, and when the spring clamp is opened, water enters the jar, and the volume of water accounts for about 1 5 of the volume of the jar. If the volume of water entering the jar is less than this value, what could be the cause? a c Fill in the serial number).

a The amount of red phosphorus is insufficient, and the oxygen in the bottle is not exhausted.

b may not be tightly corked, and the air in the bottle escapes when the red phosphorus begins to burn.

c Not cooled to room temperature.

The airtightness of the device is not good.

Experiment 2] Divide the volume of the test tube into five equal parts and mark it. Add a sufficient amount of white phosphorus to the test tube, plug the mouth of the test tube tightly with a rubber stopper, and put the test tube into hot water to make the white phosphorus burn. After the white phosphorus is extinguished and the tube has cooled to room temperature, place the tube upside down in a sink with water and remove the rubber stopper in the water.

1) In experiment two, the reason for removing the rubber stopper in water and not in air is to prevent air from entering the test tube.

2) From the analysis of the measurement results, the better effect in the appeal experiment is Experiment 2. Write two shortcomings of another experiment 1. The gas collector cylinder is too large and requires more phosphorus. 2. The air in the catheter will not be excluded, which will have an impact on the experimental results

3) The conclusion drawn from the appeal experiment about the composition of air is that air is composed of oxygen and nitrogen, and oxygen makes up about 1 5 4) The experiment also deduces that the nature of nitrogen is colorless, insoluble in water, and cannot be burned and does not support combustion

1. The error is too large. Diameter: (cm).

2. No, you should use water to make a mouth, because alcohol can kill cells.

1. The error is too large. The diameter is: (

2. No, you should use clean water.

1. Force is the reason for changing the state of motion of the object, the oars have a force on the water, and the water has a reaction force on the oars, and the boat will move forward.

2. Friction force f = multiplied by 2 times 10 = 4n, and because of uniform motion, f pushes = f = 4n

1.Experiments have shown that the plant's response to sunlight causes bending growth, which is just the plant's adaptation to light.

2.If an organism urins little or even sweats, it may live in (b).

A, grassland b, desert c, warm d, cold land.

3.The following organisms that are not environmental impacts are (d).

A, Chunjiang Plumbing Duck Prophet B, Sunflower Flowers Like the Sun C, Good Shade Under the Big Tree.

d. The spring breeze and the south bank of the Green River.

4.The four organisms (yeast, bacteria, paramecium, chlamydomonas) were classified using appropriate taxonomic methods until all four organisms were separated. (fungi, non-fungi, unicellular animals, unicellular plants).

5.In order to understand the main cause of food spoilage and the method of food preservation, a student designed the following experimental device (A and B are all clarified.

1) What is the main purpose of boiling the broth in the test tube using an alcohol lamp and other instruments after the device is placed? (sterilization).

2) What is needed in addition to the basic conditions for the living of the bacteria given in the experimental setup? What is the function of bending glass tubing? (Illumination).

3) Will the broth spoil the test tube? (a or b)a

1.Daylight 2 b 4.Fungi, non-fungi, unicellular animals, unicellular plants (1) sterilization (2) light. Comparison (3)a

(away from the plane mirror).

Meter seconds. Meter seconds.

1.The action of force is reciprocal, the paddle has a strong effect on the water, so the water also has a force on the oar, which is the reaction force.

g=10n/kg g=mg= 2kg ×10n/kg =20n

Traction force = 20n Because the average velocity moves in a straight line, thrust = traction (i.e. gravity) = 4n