8.1 - Simple reactions Flashcards
(11 cards)
What are physical changes?
Changes in substances that don’t change the substance itself.
They may alter the form of the substance but not its chemical composition.
What are physical properties?
Any measurable property of a physical system, such as:
* The colour of the substance
* The form (solid, liquid, gas)
* Boiling and melting temperatures
* Heaviness and lightness
These properties can be observed without changing the substance.
What are chemical properties?
Properties of a substance that change during or after a chemical reaction, such as:
* Acidity or alkalinity
* Reactivity with water, air, metals, etc.
* Rate and ease of reaction
These properties can only be observed during a chemical change.
What are chemical changes?
Changes in substances that form a new substance and are irreversible.
They occur during chemical reactions.
What are chemical reactions?
Processes where substances undergo changes, such as:
* Stomach acid digesting food
* Plants decaying and growing
* Atoms combining or breaking apart
These reactions can be irreversible.
What is burning?
A chemical reaction where a substance reacts with oxygen, producing new substances (oxides).
For example, burning magnesium produces magnesium oxide.
How do some substances react with water?
Some substances react violently, while others show no reaction.
Potassium, for instance, reacts violently with water vapour.
What is a physical property of potassium?
Potassium can be cut very easily.
This is a characteristic of its physical state.
What happens when potassium is placed in water?
Hydrogen gas is given off and produces enough heat to ignite the gas.
Sodium shows a similar reaction.
What happens when magnesium is placed in hydrochloric acid?
Bubbles of gas are given off, indicating new substances are forming.
This is an example of a chemical reaction.
What is the squeaky pop test?
A test to identify hydrogen gas by creating a popping sound when it reacts with a flame.
This occurs when hydrogen gas is ignited in the presence of air.
