Is it true that you get density by dividing mass by volume? and which one in the picture is denser?

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

What would be the original temperature of a gas that has a volume of 2.0 l and a pressure of 2.0 atm and an unknown temperature that the volume increased to 3.5 l in its pressure decreased to 1.0 atm if the final temperature is measured to be 11°c

If you need to add 27.50ml of a solution, which piece of glassware would you use to deliver this volume and explain how you would determine if the 27.50 ml was measured?