← Back to course
Science Launch G5 / Week 04 / Friday
5/6
Week 04 · Something New

Friday

Reaction or not?
// Mixing can make a new substance
⏱ about 15 min

Friday: Reaction or not?

Rocket pins his fizz-engine sketch to the wall. He has filled a whole notebook page with test results.

Before the test, Raven asks one more question. "Which of our experiments made something new, and which did not?"

Rocket counts on his fingers. "Salt dissolving: not new. Vinegar fizzing: new."

Nova blinks happily. "Great discovery," she says. "You are sorting changes by evidence now."

Sorting changes

Some changes only change form. Ice melting is still water. Dissolved salt is still salt.

Other changes make a new substance. We know because we see evidence like gas, a color change, a temperature change or a precipitate.

ChangeDoes it form a new substance?
Ice melts into water.?
Baking soda and vinegar fizz and make carbon dioxide.?
Salt dissolves and later comes back as salt crystals.?
Two clear liquids mix and a solid appears.?
Baking powder fizzes in water.?
WHY THIS EXERCISEGas or a new solid is evidence of a new substance. Melting and dissolving keep the same substance.
THINK IT THROUGH
  • Read the question.
  • Tap your answer.
Rocket mixes sand and salt in a jar. No bubbles, no color change, no heat. Is it a reaction?
A change that makes a new substance is a chemical ____.
Facts or observations that show something is true are called ____.
Think about it
Last week you learned weight is conserved.
Even when a new substance forms, the total weight stays the same in a closed container.

Your evidence checklist

When you see a change, run through a checklist.

Did a gas form? Did the color change? Did it get warmer or cooler? Did a solid appear?

If the answer is yes to any, you have evidence of a reaction.

USE THE CHECKLIST
  • Read the question.
  • Tap your answer.
Two clear liquids mix and turn cloudy as a solid forms. What is your conclusion?
Ice melts in a cup. Is a new substance formed?
In a closed container, what happens to the total weight during a reaction?
CHECKING A CHANGE FOR EVIDENCE
  • ?Observe the substances before mixing.
  • ?Record what you see.
  • ?Mix them carefully.
  • ?Watch for gas, color, temperature or a solid.
  • ?Decide if a new substance formed.
WHY THIS EXERCISECareful observation turns a guess into evidence.
Try it
With a grown-up, look around the kitchen for changes, like ice melting, sugar dissolving or a fizzing cup.
For each one, decide: same substance or new substance?
Draw two cups. In one, show a change of form only. In the other, show evidence of a reaction and label it.

You can now tell mixtures from reactions. Tomorrow is Launch Lab with your family.

← Thursday