How does light differ from other types of waves

What type of matter is made of only one kind of atom

Answer asap : ( a. how does mucus prevent the entry of pathogens? b. describe two ways white blood cells protect us from pathogens.

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt