Chemical Changes Notes
Chemical Changes
- A chemical change is a transformation that produces new substances with different properties from the original materials.
- Examples of chemical changes:
- An apple changing color to brown.
- A piece of wood turning into ash and smoke when it burns.
- Chemical changes happen constantly in our lives, such as:
- Our bodies processing food.
- Green plants capturing solar energy to transform carbon dioxide and water into food and oxygen.
- Cooking processes.
Fruit Ripening: A Chemical Change
- As a banana ripens:
- Its color changes.
- It becomes softer and sweeter.
Unbeneficial Chemical Changes
- Iron turning to rust.
- Food spoilage:
- Results from chemical changes where the ingredients of the food decompose.
- New substances form.
- The color changes.
- An unpleasant odor (gases) is emitted.
Milk Spoilage
- Milk spoilage is a chemical change.
Evidence of Chemical Change
- Light and Heat:
- When you light a piece of wood, it emits light and heat and turns into smoke and ash.
- Gas Formation:
- When baking soda is added to vinegar, carbon dioxide gas bubbles emerge and are released from the liquid.
- Color Change:
- Color change may be the result of a chemical change, such as when a piece of apple turns brown.
Dissolving Sugar in Water
- Dissolving sugar in water is a physical change because:
- The resulting aqueous solution retains the taste of sugar.
- The original sugar can be recovered by evaporating the water.
Cool Chemistry Experiments
- Examples of cool chemistry experiments:
- Elephant toothpaste
- Color change
- Colored fire
- Chemiluminescence
- Copper and nitric acid
- Sodium in water
- Traffic light reaction
- Thermite reaction
- Dancing gummy bear
- Sugar and sulfuric acid
- Flower shop reaction
Cool Chemical Reactions
- Luminol
- Alkali metal in water
- Thermite reaction
- Dehydration of sugar
- Copper and nitric acid
- Elephant toothpaste
- Colored fire
Signs of Chemical Reaction
- Change of color
- Change of odor
- Change of temperature
- Evolution of a gas (formation of bubbles)
- Precipitate (formation of a solid)
- Input or release of energy/heat
- Explosion
- Sound
Differentiating Chemical and Physical Changes
- Chemical and physical changes can be differentiated.