7th grade Ch. 2 Sec. 1 Observing Chemical Change

Ch. 2

Sec. 1

Observing Chemical Change

chemistry

• study of matter & its changes

2 properties of matter

2 properties of matter

1. Physical 2. Chemical

physical property

•can be observed w/o changing substance

•ex: color, temp., texture

chemical property

•ability to change

•ex: burning, rusting

Observing Chemical Change

CHANGES IN MATTER

Physical change Chemical change

Alters form or Appearance only

Produces newsubstances

EvidenceEvidenceof chemical of chemical

reactionsreactions

solid solid formedformed

colorcolorchangechange

precipitationprecipitation gas gas productionproduction

changes changes inin

temp.temp.

changes changes in in

prop.prop.

Reaction of sodium with chlorine

color change

2 types ofchemical reactions

endothermic exothermic

absorbs heatreleases

heat

Is the reaction endothermic or exothermic? Explain.

Ziploc Bag Chemistry Experiment Materials:

– 3 ziploc bags– 2 tbsp. calcium chloride– 2 tbsp. baking soda– 3 cups of water (H20)

Procedure:– Add 1 tbsp. baking soda to a ziploc bag. Place a paper cup 1/3

full of water inside the bag in the upright position. Squeeze the excess air out and seal the bag. Spill the water into the bag by shaking it. Look, listen, and feel. Record your observations.

– Add 1 tbsp. of calcium chloride to a ziploc bag. Repeat the remaining steps in #1. Record your observations.

– Mix 1 tbsp. of baking soda and 1 tbsp. of calcium chloride in a 3rd ziploc bag and mix thoroughly. Repeat the remaining steps in #1. Record your observations.

substance observation type of change

baking soda + H20

calcium chloride + H20

calcium chloride + baking soda +

H20

substance observation type of changeNaHCO3 + H20

baking soda + water

chemical or physical

calcium chloride + water

CaCl + H20

calcium chloride + baking soda + water

CaCl + NaHCO3 + H20

substance observation type of change

baking soda + H20

Cold Turned white

physical

calcium chloride + H20

ClearNo soundHotter

chemical

calcium chloride +

baking soda + H20

WhiteHotter

CracklingBubbly , foamyBag

Exploded

chemical

Fizz Whiz Soda Pop Reaction• Add 2 small scoops of the Magic Color

Crystals to the cup of water. Stir with the stick to dissolve the crystals.

• Add 2 small scoops of baking soda to the Magic Color solution. What happened to the color? Stir with the stick.

• Add a scoop of citric acid to it. What happened to the color? Stir with the stick. Add another scoop of citric acid. Take a small sip. How does it taste?

Where’s the Evidence activityReaction Observations

Before Reaction

Predictions Observations During Reaction

Observations After Reaction

Sugar White, small particles, crystals, solid

Procedure:

1. Fold up the sides of the aluminum foil square to make a small tray.

2. Use a spoon to place a pea-sized pile of sugar into the tray.

3. Describe the appearance of the sugar in your data table.

4. Secure the candle on your table in a lump of clay.

5. Predict what you think will happen if you heat the sugar. Record your prediction.

6. Use tongs to hold the tray. Heat the sugar slowly by moving the tray gently back and forth over the flame. Make observations while the sugar is heating.

7. When you think there is no longer a chemical reaction occurring, blow out the candle.

8. Allow the tray to cool for a few seconds and set it down on your desk. Record your observations of the material left in the tray.