Indicators of chemical reactions

Indicators of chemical reactions

Formation of a gas

Emission of light or heat

Formation of a precipitate

Color change

Emission of odor

OBSERVING CHANGES OF MATTER

• MATTER – Anything that has mass and

takes up space

• CHEMISTRY –The study of matter and how it

changes

T = Properties and Changes of Matter

Properties of Matter ― Physical Property ―Characteristic of a substance that

can be observed without changing the substance into another substance ―Examples – ―Melting point, color, Luster, texture,

Hardness, flexibility

T = Properties and Changes of Matter

Properties of Matter ―Chemical Property ―Characteristics of a substance

that describes its ability to change into other substances. •Examples –Burning, Rusting, Tarnishing (patina)

Chemical Properties! IDEAS?

Burning • Burnt Marshmallow • Bread to toast • Cookies in the oven • Firewood • Grass fire • ? Candle ? • Definition?

– React with Oxygen while heated!

Rusting • Bike frame • Bike Chain • Outdoor light fixtures • Lawn furniture

What RUSTS?? HOW? anything with Iron (Fe) in it!! Reacts with oxygen in water!

TARNISH?? Metal + Oxygen or

a Sulfide

T = Properties and Changes of Matter

Changes of Matter ―Physical Change ―Consists of any change which alters

the appearance or form without changes is chemical makeup changing it into another substance.

―Examples ― change of state (solid, liquid, gas),

shape, bending, crushing, cutting (ie-braiding hair)

T = Properties and Changes of Matter

Changes of Matter ―Chemical Change (chemical

reaction)

―Matter changing into a new substance

― examples, burning gasoline, burning magnesium, baking a cake

Student Activity - Classifying

Physical Change

Chemical Change

A. Piece of metal is heated until it changes to a liquid B. Two clear solutions mixed. A yellow powder forms and settles to the bottom C. Water left in a dish overnight has disappeared by the next day D. A blacksmith hammers a piece of red-hot iron into the shape of knife blade.

T = Properties and Changes of Matter

Bonding and Chemical Change ―Chemical changes occur when bonds

break and new bonds from - Review

- Bonds made by sharing or transferring electrons (what types of bonds are these?)

- Covalent vs Ionic

― O2 (in air) + Mg metal

T = Evidence of Chemical Reactions

Changes in Properties ―Precipitate

― Solid from solution ―Color Change ―Production of gas ―Change in moisture content ―Hardening

T = Evidence of Chemical Reactions

Changes in Energy — Types - Heat, light and electricity — Reaction - Absorption or release of energy ―Endothermic

― Absorption of energy (cold to touch)

―Exothermic ― Release of Energy (warm to touch)

Student Thoughts!!

Exothermic Reactions (feels warm)

Gives of Heat/Energy

• Digestion

• Burning Fuel

• Hand warmers

Endothermic Reactions (feels cold)

Absorbs Heat/Energy

• Photosynthesis

• Chemical cold pack

Assessment Questions

•

Writing a Conclusion – Power Outline

• T = Hypothesis

What happened-the results

Details—Description

Details-

Details

Hypothesis right or wrong or somewhere in between.

Details- The why!!!! (Y)

Details-

Details

Conclude with thoughts of what was made! What are your results.

Conclusion Part 2

When the sugar is heated it will come together and harden because it was a chemical change. When the sugar was heated it melted and turned brown then hardened. The sugar emitted a sweet scent. It turned a little translucent and slightly amber in hue. While it smelled sweet it also smelled slightly bitter. Our hypothesis was partially correct. The sugar turned hard but we did not think about the color change. We also did not anticipate the change in the fumes of the sugar. As the sugar was heated it carmalized and thickened.

Power Outline – 5 th Period • T= Hypothesis

The Results –What Happened-What it saw

Details –Description

Details

Details

Hypothesis- Right, Wrong, Somewhere in between

Details – what was right

What was wrong

What was missed

Propose product – what do you think the results or products is/are? Details – why? Your reasoning.

Conclusion Part 2 (P5)

If we heat the sugar, the sugar would melt because of the chemical reaction. Our lab results showed a change of color and precipitation. The sugar hardened and turned brown. It also bubbled. The aluminum turned black and candle wax melted. It smelled like the taste of a smore. Our hypothesis was correct regarding a physical change. However, it hardened, changed color and had a different smell. There was a chemical change because of the change color and smell and hardness of the browned sugar. We conclude that the sugar carmalized.

Skills Lab

• Where is the Evidence?

• PRELAB in Class. Fill out lab worksheet. Problem. Materials, Procedure, and table preparations.

• Lab – write the procedure as it is accomplished. Write down all observations in the table.

• Answer questions 1-7

• Formulate a conclusion for the lab .