An echocardiogram (echo=sound + card=heart + gram=drawing) is an ultrasound test that can evaluate the structures of the heart, as well as the direction of blood flow within it. Technicians specially trained in echocardiography produce the images and videos, often using a special probe or transducer that is placed in various places on the chest wall, to view the heart from different directions.
Cement powder is usually mixed with sand and aggregate (gravel, granite) and when needed, they are mixed with water to form concrete. Figures 4 and 5 Builders and masons, prior to the use of modern cement, used a mixture of lime (calcium hydroxide), sand and water, known as lime mortar or simply mortar.
Calcium hydroxide is formed by one #Ca^(2+)# cation and two #OH^(-)# anions, which implies that its chemical formula will be #Ca(OH)_2#. Here's how you'd figure this out. If you look at the periodic table, you'll see that calcium is in group 2. That means that it has two valence electrons that it must give up in order to be stable.