Elementary Science

Science Focus LessonPhysical and Chemical Changes

Duval County Public Schools

Essential Question:How can scientists differentiate between a physical and chemical change?

Vocabulary:Physical Chemical dissolve solution evaporate melt mixture

Remember the Matter Song?

•Matter has mass and takes up space

•Solid, liquid, gas are the three different states

•Matter has properties that tell what it’s like

• It goes through physical and chemical changes, that’s right!

Physical Properties

ColorSmellTasteVolumeMassSolubilityState or PhaseBoiling, freezing and melting point

Think Five Senses…

Physical Change

Physical changes occur when matter changes its physical property but not its chemical nature.

Physical property changes could include changes in: texture, shape, size, color, odor, volume, mass, weight, and density.

These changes can be reversed!

Physical Change

The shape and volume was changed but the chemical make-up remains the same. It’s still H20!

Physical Change

The shape was change but the mass remains the same!

Physical Change

The shape and state was changed but the mass and volume remains the same! Ah, but

how can I reverse it?

Summarizing

Think…Pair…SharePartner A to Partner B: Name an

example of a physical changePartner B to Partner A: Explain why

that example is a physical change?Both partners: Find this part of the

Matter Song in your IAN’s!

In a physical change, the object stays the sameYou can fold it, bend it, cut it, but the object still remainsA physical change doesn’t really change the matterThe matter just moves from one state to another…

Chemical Properties

Indicates how a substance reacts with something else.

The original substance is changed into a different substance.

Think Five Senses…

Chemical Change

Chemical changes are changes matter undergoes when it becomes new or different matter.

These changes Cannot be reversed!

Signs of a Chemical Change•Evidence of a chemical reaction•Formation of gas – bubbles! •Formation of a new substance -- rust•Change in color -- leaves•Gives off Light – glow stick•Change in thermal energy

•Endothermic Absorbs heat energy (gets cold) – cold pack

•Exothermic Releases heat energy (gets hot) – hand warmer

Chemical Change

Each of the original ingredients now have different physical and chemical properties than the final product

does!

Chemical Change

The original material now has different physical and chemical properties than the final product does!

Chemical Change

The original substance now has different physical and chemical properties than the final product does!

SummarizingThe most important thingPair Share: Partner A tell B what the most

important thing is that you learned from this lesson…why?

Partner B tell A what the most important thing is that you learned from this lesson…why?

Both partners, find this part of the Matter Song!

In a chemical change, a new substance is createdYou can rust it, burn it, cook it, but you can’t reverse itIn a chemical change something new will formEnergy is given off or energy is absorbed!

Physical Change Chemical Change

Temperature and Change!What will happen to a substance if heat is

added to it? What would happen if the temperature is decreased?

http://youtu.be/j6KGXZ3m6ys

Guided Instruction:1. Claire adds 10 grams (g) of salt to a jar of cold water. She then adds 10 g of salt to a second jar of hot water. She covers and shakes both jars and sets them on the table for five minutes. The materials Dani used are shown below. What should Dani expect to observe after those five minutes?

a. In both jars, the salt dissolved at the same rate. b. The salt in the jar with hot water dissolved slower. c. The salt in the jar with the cold water dissolved slower.d. The salt remained at the bottom of both jars in equal

amounts.

The answer is CWhen matter dissolves in water with more heat energy, it forms a solution faster. Salt will form a salt water solution when mixed with water, sand does not dissolve in water and will sink to the bottom.

Guided Instruction:2. Markell wants to do an investigation to see how heat affects a physical change in a substance. Which of the following is an investigation he can conduct?

a. Add heat to a marshmallow to see how long it takes to burn.b. Remove heat from water to see how long it takes for sugar to

dissolve.c. Add heat energy to different sizes of paper to see if larger

pieces take long to burn than smaller ones.d. Test batteries from the freezer against batteries from a hot car

to see which last longest in a flashlight.

The answer is BDissolving sugar in water is a physical change. The sugar can be reclaimed by evaporating the water. All of the other choices are chemical changes because the substances are changed irreversibly.

Guided Instruction:3. Laila left her balloon in the car on a hot day. When she came back to the car, the balloon had popped. What most likely happened to the balloon?

a. The air molecules inside the balloon combined to form a solid.b. The balloon got smaller and squeezed out the air.c. The air inside the balloon heated up and expandedd. The air inside the balloon condensed into a liquid.

The answer is CMost matter expands when thermal energy is added to it. Her balloons were filled with helium that expanded as the temperature went up. At some point, the balloons popped because the gas expanded as it warmed. Remember the bubble experiment?

SummarizingTalking ChipsOne at a time, each team mate tell the

others what science finding surprises you the most!

Check Your Understanding1. Builders leave gaps, or spaces, between the parts of a metal

bridge. They do this so the bridge can change when it gets hot. Based on this, what most likely happens to metal when it is heated?

A.) Most metals expand when they are heated.

B.) Most metals contract when they are heated.

C.) Most metals change into other substances when they are heated.

D.) Most metals crack when they are heated.

Check Your Understanding2. One way weathering happens is when water gets inside the

cracks of rocks and boulders in colder regions. What most likely causes this to happen?

A.) Most rocks have water in them, and it wears the rocks down.

B.) As the water gets in the cracks, it expands as it heats up.

C.) As water freezes, it contracts in the cracks and pulls the cracks wider.

D.) As water freezes, it expands in the cracks and pushes the cracks wider..

Check Your Understanding3) Raina was investigating physical and chemical changes for her

science fair project. She was mixing different chemicals together and observing their reactions. Which of the following is a common sign that a chemical change has occurred?

A.) A chemical has changed size.

B.) A chemical has turned a different color.

C.) A chemical has become a different shape.

D.) A chemical has changed to a different state (solid, liquid or gas)

Check Your Understanding4. Teron draws a picture on a piece of paper and then folds it into a

paper airplane. He throws it at King, and its hits him in the head. He responds by ripping up the paper. Which of the following is an example of a physical change?

A.) ripping up the paper

B.) folding the paper into an airplane

C.) drawing on the paper

D.) all of these

Check Your Answers1. A. Most matter expands as it heats, but not

water, it expands as it freezes.

2. D. As water freezes, it expands in the cracks and pushes the cracks wider.

3. B. A chemical has turned a different color.

4. D. all of these

Quick Write:

How can scientists identify and physical and chemical change?

Summary Question