Is freezing water a physical or chemical change

The reactions of photosynthesis occur in the of plant cell? a. mitochondria. b. lysosomes. c. chloroplasts. d. chlorophyll

Astring vibrates with a frequency of 10 hz. why can't a person hear the sound waves produced by the vibrating string, no matter how large the amplitude of the waves? out! this is homework and due tomorrow! you so much!

How many neutrons does an element have if its atomic number is 50 and its mass number is 166