Which are easier to reverse - chemical or physical changes

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Where does rusting start

A car's paint could get chipped rusting starts there

What people call a chemical change

A chemical reaction

Sodium carbonate

A harmless solid

The substances of stainless steel

Chromium is mixed with nickel with the other substances in steel

Signs of a chemical changes

Color change, formation of a gas, and heat changes

The reaction between vinegar and baking soda

Example of a chemical change

Cookware in the kitchen

Exposed to moisture

Do foods contain sulfur?

Foods contain sulfur, particularly eggs

What happens when baking soda and vinegar are mixed

Gas bubbles form

How to remove tarnish

Polish the tarnished item

How chemical changes occur

Chemical changes occur when atoms link together in new ways

Rocket engines use a lot of heat

Chemical reactions produce lots of heat

What happens when solid fuel burns

Aluminum powder is converted to aluminum oxide

New substances formed by chemical reactions

Called products

The original substances of chemical changes

Called reactants

Special type of steel

Called stainless steel

Unburning toast

Can not unburn toast

Unspoil milk

Can not unspoil milk

Ingredients of baking soda and vinegar

Carbon dioxide gas, water, and sodium acetate

The new substance of baking soda and vinegar

Creates carbon dioxide, and other new substances you can not see

Reversing chemical changes

Difficult to reverse

How to slow down rusting

Painting or oiling steel and other complex steel

The chemical change of a cake

Heat turns the baking soda in the cake dough into sodium carbonate, steam, and carbon dioxide gas

The bubbles of carbon dioxide in the cake

Help the dough expand and make the cake light and fluffy

The steam in the cake

Helps make the cake moist

Wax into carbon dioxide

Turns into carbon dioxide gas and steam when it combines with oxygen in the air

What does zinc do?

In moist air zinc form a self - protecting coating

Iron oxide

Is a red powder, commonly known as rust

Objects covered by tarnish

Is silver sulfide

The reaction of rust

Is very complex and needs moisture to occur

Where is rusting starting

It comes in side to out

Reversing sugar water

Let the water evaporate

Reversing an ice cube

Melting an ice cube can be easily be reversed by cooling it until it freezes again.

The wax of a burning candle

Melts, runs down the side and turns solid again

What produce small amounts of hydrogen sulifde

Mineral springs contain small amounts of hydrogen sulfide

Galvanizing bath

Objects are given a thin coat of zinc

The main engines of space shuttle

Powered by liquid nitrogen and liquid oxygen

The affect of rusting

Rust eats through iron containing metals and weakens the metal which makes the metal destroyed

Reversing physical changes

Sometimes easy to reverse

How rust occurs

Steel objects are most likely to rust if they get wet and not dried right away

Making the candle flame

The change releases enough heat to make the candle flame

Properties of chemical change

The new substances have properties different from the original substances from which they formed

The chemical reactions formed in the cake

These chemical changes strengthen the cake and keep it from collapsing after it is baked

When liquid nitrogen and liquid oxygen

They make water vapor

The heat of the oven on the cake

Triggers other chemical changes in the cake batter

What the shuttle boosters use

Uses a solid fuel

How rust forms

When iron atoms in steel react with oxygen from the air

How silver sulfide forms

When silver in the object reacts with sulfur or hydrogen sulfide in food or the air

Reversing a piece of paper after cutting it

Will not be easy to put the paper back after cutting it

How to prevent rusting in those places

You could sand or repaint those places

How to tarnish silver

You could wrap it with a rubber band

Does zinc rust?

Zinc does not rust

Does zinc protect steel?

Zinc protects the inner coat of metal objects from rusting


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