UNIT 1 Matter Day 8 Monday, September 11, 2017 Physical and Chemical Changes of Matter 8th Grade Science

September 11, 2017 1. Turn in any late flash cards. NOT 12-16 September 11, 2017 1. Turn in any late flash cards. NOT 12-16. Make sure they are numbered, in order, and your name is on them. No late cards will be accepted after today. 2. Warm-up – Complete the “Physical vs. Chemical Properties” ½ sheet. Work Quickly. Go!!!

Sept. 11, 2017 Plan for today 1. Science Starter 2. E. Q. 3. Discuss tonight’s homework 5. Review effects of temperature on density 6. Lesson – Chemical Change -Notes -Video 7. Oobleck Lab 8. Wrap-up

Copy on Page 11 Essential Question -How are chemical changes different from physical changes?

Homework: Make a flash card for term #17 “Chemical Change”. Flash cards 12-17 and your vocab. sheets are due Wednesday. Make sure they are complete. “Two Ways to Change” wkst. - due tomorrow. CFA Wednesday over physical and chemical properties and physical and chemical change.

A few more things about heat and density…

Why are some objects less dense than other objects? The further apart the molecules of a substance are, the lower its density.

What causes molecules to spread? Adding energy (usually in the form of heat) so the movement of the molecules increases.

Objects float in other substances because they are less dense than the substance they are floating in. Why does ice float in water? They are both the same substance, right?

The spaces between the atoms make solid water less dense. Notice how tightly packed the atoms are in the liquid water vs the solid water? The spaces between the atoms make solid water less dense. Is this true for all solids? NO WAY!!! This is a unique quality of water. Most solids are always more dense than their liquid forms.

DENSITY When does an object’s density change? If heat is added or taken away!!!! HEAT – spreads out molecules and makes them LESS dense Take AWAY heat – molecules come together and makes them MORE dense. Water vapor (gas…particles have a lot of energy and are moving fast) is less dense than liquid water! Hot water is less dense than cold water.

To recap… Density is a result of how tightly atoms/particles are packed in a given space. Heat affects density. As heat (thermal energy) is added, particles become more energized and move further apart. Density then decreases.

Reviewing Physical Change… A PHYSICAL change does not result in a new substance being formed. It only changes the appearance of a substance. Ex. Melting ice – Solid water Liquid water It’s still water!!!!! Ex. Shaping a gold bar into jewelry It’s still gold!!!!

18. Chemical change Def. - a CHANGE that happens when two or more substances combine (react with one another) and form a new, different substance AD – the composition/identity of the matter is changed AD – the new substances have new properties (iron is magnetic but rust…the new substance, is NOT magnetic) Ex: milk souring, apples browning, baking a cake, fireworks, copper turning green (oxidizing), nail rusting, wood burning

another example of how a Chemical change produces new substances with different properties… Sodium and chlorine are elements on the periodic table of elements. They are very reactive and combine easily with one another. Sodium is a silvery metal that is soft enough to be cut with a knife. Chlorine is a greenish-yellow poisonous gas. When sodium and chlorine react with one another, they produce SALT. Salt is NOT silvery or soft, it is NOT greenish-yellow, it is NOT poisonous, and it is NOT a gas.

Signs of a Chemical Change: distinct color change, odor produced, energy in the form of heat or light, bubbling or fizzing, the formation of a precipitate indicate a chemical change has occurred. Ex: Fireworks; When baking a cake, odor, browning and air pockets in the cake indicate a chemical change occurred. A gas is produced. This is why cake is spongy. Precipitate: the cloudy solid that results when two liquid substances are combined.

Let’s watch a video to help us better understand chemical changes! Video on chemical changes

RECAP-physical vs. chemical changes Physical changes don’t change the composition/identity of the substance, only its appearance or form. Chemical changes always result in NEW substances with different properties. Composition: the type of matter making up a substance and how matter is arranged in the substance.

Oobleck Lab

The Oobleck has been prepared for you ahead of time *The Oobleck has been prepared for you ahead of time. (If you want to make it at home, it's 2 parts cornstarch to 1 part water:) Procedure: 1. You will work together as a group (and you know I mean it). 2. Work as a group, but complete your own worksheet. 3. As a group, discuss and complete the Pre-Investigation Review on the "Monster Muck" sheet. 4. There are 8 tests to complete with the Oobleck. They are on the laminated sheet at your table. Allow everyone to test the Oobleck. But keep in mind that you have an observation sheet to complete so test, record, and move on. 5. When you finish the 8 tests, answer the questions on back of your worksheet. Clean up your table.

https://www.youtube.com/watch?v=D-wxnID2q4A

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Wrap-up: Answer today’s E.Q.