1. Mass is measured with and instrument called a 2. When using a balance, the object to be measured
is placed on the

Two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate? a) produce x-rays using colliding electrons and send them to radios, which capture sound b) send messages using infrared radiation, which travel in the form of waves c) send radio waves through intervening media like radio and television d) produce sound waves using microwaves from heated objects

Compare and contrast physical changes with chemical changes.

How are isotopes of the same chemical element alike? how are they different?