A teacher writes 2 H2 + O2 gives 2 H2O on the board and points to the H2O. What is that substance called in this reaction?

In the equation 2 Mg + O2 gives 2 MgO, a student asks what the large 2 written in front of MgO is called. What is the correct term for it?

Students drop zinc pieces into hydrochloric acid. The zinc slowly shrinks, bubbles of a gas that pops when lit rise, and the test tube grows warm. What has taken place inside the tube?

A sealed flask of baking soda and vinegar is weighed before and after it fizzes, and the balance reads 82.4 g both times. Which idea does this observation show?

A candle burns on an open balance and the reading falls steadily as gases from the flame drift away into the room. What kind of system is the student weighing?

Overnight the air temperature falls below 0 degrees Celsius and a puddle of liquid water on a driveway becomes solid ice. Which term names this change of state?

A hand warmer packet gets hot after it is opened, because the iron powder inside reacts with oxygen from the air. Which term describes this reaction?

A girl presses the plunger of a sealed syringe and the matter inside is squeezed into a much smaller space, then pushes the plunger back out. Which state of matter behaves this way?

On a humid afternoon, drops of water collect on the outside of a cold glass of iced tea that nobody has spilled. Which process put the water there?

A student stirs sugar into hot tea and keeps stirring until the sugar crystals can no longer be seen anywhere in the cup. Which term describes what happened to the sugar?

A blacksmith hammers a bar of iron into a flat sheet. The sheet has a new shape, and tests show it is still iron. Which term describes the change?

As a nail rusts, iron and oxygen combine and iron oxide builds up on the surface. Which term names the iron and the oxygen in this reaction?

A student mixes two chemicals in a plastic cup. The thermometer in the cup falls from 22 degrees Celsius to 8 degrees Celsius and the cup feels cold. Which term describes the reaction?

Blocks of dry ice on a stage give off a thick cloud of carbon dioxide gas, and no puddle of liquid is ever left behind. Which process is this?

A lab report reads: 'We poured the two clear solutions together and a cloudy yellow solid settled to the bottom. That solid is called a ___.' Which term completes the sentence?

A lab report reads: 'We counted the same number of each kind of atom on both sides of the arrow, so our equation is ___.' Which term completes the sentence correctly?

A write-up reads: 'In H2O, the small 2 printed just after the H tells how many hydrogen atoms are in one molecule. That small number is called a ___.'

A report reads: 'We heated the water and its particles moved faster and spread further apart. The energy we transferred into the water is called ___ energy.'

A report reads: 'Powdered chalk fizzed away in acid in 20 seconds, while the same mass of chalk lumps took 90 seconds. Powdering the chalk increased the ___.'

A report reads: 'We stoppered the flask so that no gas could escape, and the mass on the balance stayed the same. We ran the reaction in a ___.'