Mass stays the same in a reaction
Grade 8 Science Worksheet
Circle the best answer, or write your answer on the line.
Bo's teacher mixes 130 g of one solution with a second solution in a sealed jar. The products total 200 g. What was the mass of the second solution?
Before, iron 56 g and oxygen ? g; after, rust 80 g. Jun reads the table for steel wool rusting in a sealed jar. How much oxygen joined the iron?
Before, copper 64 g and oxygen ? g; after, copper oxide 80 g. A teacher heats copper powder in a sealed tube and it turns into black copper oxide. Using the table, how much oxygen joined the copper, Kira?
Before, hydrogen peroxide 68 g; after, water 36 g and oxygen ? g. In a teacher's sealed flask, yeast helps hydrogen peroxide break down into water and oxygen. Using the table, how much oxygen formed, Luz?
Milo leaves steel wool in an open dish on a scale. Over days it rusts and the reading goes up. Why?
- Rust is new matter made in the dish
- Oxygen from the air joined the iron
- The dish got heavier by itself
- Water evaporated from the dish
Noah's book says a burned log leaves ash that weighs far less than the log. Where did most of the mass go?
- It was destroyed by the burning
- Into gases, which weigh nothing
- Into the ground under the fire
- Into the air as gases
A fizzing tablet in an open cup makes the scale drop by 4 g. Where did the 4 g go, Pia?
- Into the cup's walls
- Into the air as carbon dioxide gas
- Nowhere: gas bubbles weigh nothing
- It was used up by the fizzing
Ren graphs the same fizzing reaction twice: once in an open cup (line P) and once in a sealed bottle (line Q). Which line shows conservation of mass?
- Line P: its mass changed, so it reacted more
- Both lines equally
- Line Q: nothing could escape
- Neither: mass drops in reactions
In Tala's open-cup graph, the mass falls from 300 g to 296 g. What was the mass of the gas that escaped?
- 0 g: gases weigh nothing
- 296 g
- 300 g
- 4 g
Zee's open dish of steel wool rusts, and its mass rises from 150 g to 153 g. How much oxygen joined from the air?
- 153 g
- 3 g
- 303 g
- 0 g: air adds no mass