Chemical and Physical Change
A change that does not create a new substance.
What is a physical change?
This type of pure substance cannot be broken down into simpler substances by chemical means.
What is an element?
A mixture where components are evenly distributed and not visible
What is a homogenous mixture?
When a substance can dissolve in another substance, typically a liquid.
What does it mean when a substance is soluble?
The amount of solute dissolved in a given amount of solvent.
What does concentration mean in a solution?
Rusting, burning, or cooking an egg.
Give an example of a chemical change.
An example of a pure compound with two hydrogen atoms and one oxygen atom.
What is water (H₂O)?
Fruit Salad or Trail Mix
Give an example of a heterogenous mixture you might find in your kitchen.
Temperature, stirring, and particle size
Name three factors that affect the rate of dissolving.
The solution becomes less concentrated with a lower solute-to-solvent ratio. This is dilution.
Describe what happens when you add more water to a concentrated solution. What is it called?
- changes do not create new substances and can be reversed, while - changes form new substances with different properties
Explain how you can distinguish between a physical and chemical change?
An element consists of only one type of atom, while a compound is made of two or more different types of atoms chemically bonded together.
Explain the difference between an element and a compound at atomic level.
A - has larger particles that will eventually settle, while a - has smaller particles that remain evenly distributed and do not settle.
Describe the difference between a suspension and a colloid.
- occurs when no more solute can be dissolved in a solvent at a given temperature.
Explain the concept of Saturation in a solution.
- Add more solute
- Remove some solvent
- Allow solvent to evaporate
Explain three ways to increase the concentration of a solution.
Chemical reactions often involve energy absorption (endothermic) or energy release (exothermic).
Describe the energy changes typically associated with chemical reactions.
Two elements found in the periodic table that are liquid at room temperature.
What are mercury and bromine?
- is a special type of mixture where two liquids that normally don't mix are suspended together, like milk or mayonnaise.
Explain how emulsion differs from other types of mixtures.
Generally, higher temperatures increase solubility, allowing more solute to dissolve.
How does temperature influence the solubility of a slid in a liquid?
- Percentage (%)
- Parts per million (ppm)
- Molarity (moles of solute per litre of solution)
How do scientists typically express concentration?
Chemical changes involve breaking and forming chemical bonds, resulting in a complete transformation of the original substances.
Discuss how atomic rearrangement occurs during a chemical change.
24 carat is pure gold with no other metals. Lower caratages contain less gold; 18 carat gold contains 75 per cent gold and 25 per cent other metals, often copper or silver.
What is the difference between pure gold and impure gold?
Smaller particle sizes can increase surface area, which affects dissolution rate, mixture stability, and chemical reactivity.
Discuss how particle size affects the properties of a mixture.
Solute particles break apart and interact with solvent molecules, forming new interactions and distributing evenly throughout the solution.
Describe the molecular interactions that occur during the dissolution process.
When water is added to a solution:
- Solute particles become more spread out
- Intermolecular interactions change
- Overall concentration decreases
- Total amount of solute remains the same
Describe the molecular interactions that occur during dilution.