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Science Launch G5 / Week 04 / Tuesday
2/6
Week 04 · Something New

Tuesday

Clues of a reaction
// Mixing can make a new substance
⏱ about 15 min

Tuesday: Clues of a reaction

Raven pins four cards to the corkboard in the workshop. Each card has a drawing: bubbles, a color wheel, a thermometer and a cloudy cup.

"These are the four signs," she says. "Scientists look for them after mixing."

Rocket squints at the cloudy cup. "Why is that one a clue?"

Nova shines a light through a cup of clear water. "What do you notice when a solid suddenly appears in a clear liquid?" she asks.

"Something new was made," Rocket says. "It did not exist a second ago."

Four kinds of evidence

Scientists use four kinds of evidence to tell that a chemical reaction happened.

EvidenceWhat you observe
Gas is producedBubbles or fizzing appear
Color changeThe mixture turns a new color
Temperature changeThe mixture gets warmer or cooler
A precipitate formsA solid appears when two liquids are mixed

Seeing one of these is good evidence. Seeing more than one is even stronger.

Bubbles are evidence that a ____ was produced.
A solid that forms when two liquids mix is called a ____.
If a mixture gets warmer or cooler, that is a ____ change.
SPOT THE EVIDENCE
  • Read the question.
  • Tap your answer.
Two clear liquids are mixed and a white solid appears. What is the evidence called?
Which is NOT one of the four kinds of evidence?
Careful
In a lab, you never feel a mixture with your hands or taste it.
A grown-up can check temperature with a thermometer.

Stronger with more clues

One clue is good evidence of a reaction.

Two or more clues together make the case even stronger.

Scientists write down every clue they observe, not just the first one.

ObservationIs it evidence of a reaction?
A mixture suddenly turns purple.?
A mixture gets warm by itself.?
A powder is poured into a cup.?
Fizzing bubbles appear.?
WHY THIS EXERCISEColor, temperature, gas and precipitates are clues. Pouring is just an action.
WHICH CLUE?
  • Read the question.
  • Tap your answer.
A mixture turns from blue to green. Which kind of evidence is this?
A mixture gets cooler as you watch the thermometer. Which kind of evidence?
Who should check a mixture's temperature?
How many kinds of evidence of a reaction did you learn today? Type a number.
WHY THIS EXERCISEGas, color change, temperature change and a precipitate make four.
Try it
Make four clue cards like Raven's: bubbles, color, thermometer and a cloudy cup.
On the back of each, write what you would observe.
◈ COMBINE AND CHECK

Press each step to mix the starting materials on the bench.

Guess first: is it the same stuff, or something new? Then read the clue under the badge.

You now know what to look for. Tomorrow you will collect your own evidence.

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