Mass stays the same in a reaction
Grade 8 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
In a teacher's sealed flask, 60 g of one clear solution reacts with 15 g of another, and a yellow solid forms. Total after = total before. What is the mass after, Ari?
Bo watches a sealed jar: 120 g of solution and a 30 g tablet react and fizz inside. Total after = total before. What is the total mass after?
Steel wool (85 g) rusts inside a sealed jar holding 40 g of air. Total after = total before. What is the total mass after, Esme?
Next, the teacher fizzes the same tablet in a sealed bottle on the scale. What does the scale show, Kira?
- Less, as the fizz uses up mass
- More, as the bubbles push down
- Zero, once the tablet is gone
- The same mass as before
Luz wants a setup that shows mass is conserved. Which one works best?
- A container with a hole in the lid
- An open cup, so the gas has room to spread out
- A sealed container: nothing gets in or out
- An open cup, since gas adds no mass
Milo graphs a sealed flask's mass while two solutions react inside. What happens to the mass?
- It rises, as new products form
- It drops to 0 g
- It drops, as the reactants are used up
- It stays at 200 g
Pia graphs a sealed jar of steel wool as it rusts over 5 days. What happens to the mass?
- It drops, as the iron is used up
- It stays at 300 g
- It doubles
- It rises, as rust is new matter
Ren's glossary has a blank by conservation of mass. Which meaning fits there?
- Mass is destroyed when things react
- Total mass before a reaction = total mass after
- New substances bring new mass
- Solids keep their mass, but a gas weighs nothing
Tala reads about atoms in a reaction. What happens to them?
- They are rearranged into new substances
- New ones are made as products form
- They turn into light
- Some are destroyed and replaced
A reaction runs in a sealed jar. Why does its total mass stay the same, Zee?
- Products are lighter but bigger
- The same atoms are there, joined differently
- The jar stops the reaction
- Any gases made weigh nothing