1. What are the wavelengths of sound waves at the limits of human hearing - 20 Hz and 20 kHz? The speed of sound in 20 ºC (72 ºF) air is 343 m/s

2. The wavelength of microwaves in an oven is 12 cm. What is the frequency of the waves?

3. What is the frequency of a photon that has a wavelength of 4.87 x 10^7 m?

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance