Unit 7 Lesson 1 Physical and Chemical Changes

What are some observable changes that often accompany chemical changes?

1. Production of odor (like egg rotting or milk getting sour) 2. Production of a Gas (fizzing or foaming, like when a antacid tablet in water forming carbon dioxide gas) 3. Formation of a Precipitate (like colorless potassium iodide & lead nitrate when combined form a yellow precipitate lead iodide) 4. Change in Energy (burning of a candle coverts to heat & light energy) 5. Change in Color (when gray iron rusts, it forms to a brown product)

physical change

A change that affects one or more physical properties of a substance.

chemical change

A change that occurs when one or more substances change into entirely new substances with different properties.

Physical property of matter

A characteristic of a substance that can be observed and measured without changing the chemical identity of the substance

What is the difference between a chemical property and a chemical change?

A chemical property of a substance determines wether a chemical change can occur. A chemical change is the actual process of changing.

precipitate

A solid that forms from a solution during a chemical reaction.

What are some observable properties of a physical change?

Appearance Shape Size

Is it a physical or chemical change that results in the formation of a new substance?

Chemical

The formation of a precipitate signals a physical or chemical change?

Chemical

Is burning or dying wool an example of a physical change?

Dying

Law of Conservation of Mass

In ordinary chemical and physical changes, mass is not created or destroyed but is only transformed into different substances.

Sharpening a pencil leaves behind pencil shavings. Is sharpening a pencil a physical change or a chemical change? Explain.

It is a physical change. The pencil's shape and mass changed.

One Example of conservation of mass in a physical change is

Removable parts to construct a robot, can change the look by rearranging the parts but it is still a toy robot.

Examples of chemical change

Rusting of iron nail Baking a cake frying an egg mixing baking soda and vinegar Burning logs in a campfire Digesting food Mixing an acid and a base Explosion of fireworks Milk going sour Rotting bananas

When turn wool into a sweater requires what kind of physical changes?

Sheared from a sheep Cleaned Fibers are separated Spun into yarn Dyed Knitting These change the shape, volume, and texture of the wool; but does not change the wool into another substance.

Suppose a log's mass is 5 kg. After burning, the mass of the ash is 1 kg. Explain what may have happened to the other 4 kg.

Smoke and gases have been released into the atmosphere when the log was burning.

Examples of a purely physical change are:

Stretching a rubber band Dissolving sugar in water Cutting your hair Melting butter Freezing water into ice cubes Boiling water Crushing a soda can Chopping wood Shredding paper Breaking a glass

Water may freeze or the ice may melt, but the amount of Matter in a glass will remain the same is an example of ____________________________________.

The law of conservation of mass

How do higher temperatures influence a chemical change?

The reactions often happen more quickly; the particles in a substance have more average kinetic energy and move around a lot more freely and so rearrange more easily.

As the bright sun shines upon the water, the water slowly disappears. The same sunlight gives energy to the surrounding plants to convert water and carbon dioxide into sugar and oxygen gas. Which change is physical and which is chemical?

The water disappearing is a physical change (evaporation) and water and carbon dioxide converting to sugar and oxygen gas is a chemical change.

How is a chemical change different from a physical change?

There are several differences between a physical and chemical change in matter or substances. A physical change in a substance doesn't change what the substance is. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.

How does a physical change occur?

When a substance changes from one form to another; the chemical identity of the substance remains the same.

One example of conservation of mass in a chemical change is

When vinegar & baking soda are combined in a beaker they produce a chemical change of carbon dioxide but when put a balloon on top and it catches the chemical change of the carbon dioxide, the mass of the starting materials is the same as the mass of the products.

Relate the statement "You can't get something for nothing" to the law of the conservation of mass.

You cannot create mass from nothing.