Which of these is an indication that a chemical reaction has occurred?

1) melting of a substance

2) boiling of a substance

3) formation of a precipitate

4) freezing of a substance

What causes static electricity

All visible light (light that our eyes can detect) has a wavelength between 400-700 nanometers.  Wavelengths just smaller than 400 nm are ultraviolet light.  Wavelengths just larger than 700 nanometers are infrared light.

Why do all parts of our solar system orbit around the sun

What is the correct displacement for the following vectors: 4 km south, 2 km north, 5 km south, and 5 km north? 2 km south 16 km total 11 km west 6 km south

A uniform electric field with a magnitude of 125 000 N/C passes through a rectangle with sides of 2.50 m and 5.00 m. The angle between the electric field vector and the vector normal to the rectangular plane is 65.0°.

Two small plastic spheres between them has magnitude 0.22 N. What is the charge on each sphere is one the other? Explain whether it can be determined from the information give, whether the charges are positive or negative.

If it has enough kinetic energy, a moleculeat the surface of the Earth can escape the Earth's gravitation. The acceleration of gravity is 9.8 m/s2, and the Boltzmanns' constant is 1.38066*10-23 J/K.

True or False. Alcohol is toxic to most fruit flies, but fruit flies that metabolize alcohol quickly survive alcohol exposure better than normal metabolizers.

Aerobic exercise is exercise where oxygen is not present. Question options: True False

The force between a pair of. 005 charges is 750 N. What is the distance between them?