Make-up quiz on Friday for everyone.

Office hours Thursday afterschool. If you have questions, COME SEE ME.

Workbook pages 1-19

All pages up to page 19 should be completed in your workbook by now.

Page 27 questions 1-3

Any change that alters the form or appearance of matter but does not make any substance in the matter into a different substance.

A substance that undergoes physical change is still the same substance after the change

We know that matter has three states: Solid Liquid Gas

What are some examples of each?

Let’s say you left a puddle of water on the kitchen table. A few hours go by, you come back, and the puddle is gone.

Did the water disappear? No, a PHYSICAL CHANGE occurred. The

liquid water changed into water vapor (a gas) and mixed with the air

A change in state (from solid to liquid or gas) is a physical change

Is there a physical change when you dissolve sugar or salt in water?

To be sure, you need to make sure that the salt or sugar hasn’t changed into a new substance.

For example, we know that sugar is sweet. A sugar solution is as sweet as the undissolved sugar. It’s still SUGAR.

Physical changes include: Dissolving Bending Crushing Breaking Chopping Filtration distillation

A change in matter that produces one or more new substances is a chemical change (or chemical reaction).

A single substance changes to one or more other substances

One example is when hydrogen peroxide is poured on a cut on your skin, it breaks down into water and oxygen gas.

When natural gas burns on a stove (methane), it combines with oxygen in the air and forms new substances-carbon dioxide and water vapor

Chemical Change Description Example

Combustion Rapid combination of fuel with oxygen; produces heat, light, and new substances

Gas, oil, or coal burning in a furnace

Electrolysis Use of electricity to break a compound into elements or simpler compounds

Breaking down water into hydrogen and oxygen

Oxidation Slow combination of a substance with oxygen

Rusting of an iron fence

Tarnishing Slow combination of a bright metal with sulfur, producing a dark coating on the metal

Tarnishing of brass

Vanessa Turchan

Vanessa Turchan

Vanessa Turchan

Vanessa Turchan

One example of a physical change is: A)burning paper B)baking cookies C)heating table sugar D)dissolving salt in water

The answer is D- dissolving salt in water

One example of a chemical change is: A) filtering B)burning wood C)boiling water D)crushing a can

The answer is B- burning wood

Law of conservation of mass: matter is not created nor destroyed in any chemical or physical change

Since mass measures matter, this can also be called the conservation of matter

Let’s look at the example on page 25 of methane gas burning.

For every molecule of methane that burns, 2 molecules of oxygen are used. The atoms re-arrange, but do not disappear during the reaction.

Energy: the ability to do work or cause change

Every chemical or physical change in matter includes a change in energy

Temperature: a measure of the average energy of random motion of particles of matter.

Warmer particles have greater average motion than cooler particles.

When matter changes, the most common form of energy released or absorbed is thermal energy

For example, ice absorbs thermal energy from its surroundings and melts.

The melting of ice is an ENDOTHERMIC change

Endothermic: a change in which energy is taken in, or absorbed.

Exothermic: releases energy. Combustion is an example of

exothermic change because it releases energy in the form of heat.

When you see fireworks in the sky, what kind of thermal energy are you seeing?

When ice melts, is thermal energy released or absorbed?

Fireworks give off energy in the form of heat and light, so it’s an exothermic change.

Ice melts because it absorbs heat from the environment, making this an endothermic change.