Unit A Energy and Matter in Chemical Change : Section 1.0 Flashcards
What does WHMIS stand for?
Workplace Hazardous Materials Information System
What is MSDS?
Material Safety Data Sheet
Identifies physical and chemical hazards associated with a product
Generally, what do Physical Properties describe?
They describe the physical appearance and composition of a substance
What are the common Physical properties
- Boiling point
- Melting point
- Freezing point
- Malleability
- Ductility
- Colour
- State
- Solubility
- Crystal formation
- Conductivity
- magnetism
Generally, what do Chemical properties describe?
The reactivity of a substance
What are the common chemical properties?
- Ability to burn
- Flash point
- Behaviour in air
- Reaction in water
- Reaction with acids
- Reaction with heat
- Reaction to litmus paer
What is a flash point?
Temperature needed to ignite a flame
What happens if a substance undergoes a physical change?
It still has all the same properties and is reversible
What happens if a substance undergoes a chemical change?
A new substance is formed and it is irreversible
What are the two classifications of matter? Define both.
Pure substance: matter that has definite composition
Mixture: combinations of matter that can be separated by physical means; do not have definite composition
What is a pure substance?
All the particles that make up the substance are chemically combined and identical; they have definite composition (atoms within are in fixed proportions due to their bonds to one another)
What are the two types of pure substances? Define both.
Element: cannot be chemically broken down into simpler substances
Compound: two or more elements that are chemically combined; can be separated chemically into simpler substances
What is an element?
A pure substance that cannot be broken down chemically into other substances and made of only one type of atom
What is a compound?
An group of elements that are chemically combined in fixed proportions
What is a mixture?
A combination of matter that can be separated by physical means. Proportions of one pure substance to another making the the mixture can vary.
Mixtures can be heterogeneous or homogeneous:
What is a mechanical mixture / heterogeneous mixture?
When the different components are visible such as soil
The composition of the material is variable throughout the mixture
What is a suspension?
A type of heterogeneous mixture where the components are in different states such as mud
Mud or muddy water: where soil, clay, or silt particles are suspended in water.
Flour suspended in water.
Kimchi suspended on vinegar.
Chalk suspended in water.
Sand suspended in water.
Suspensions have larger particles than colloids so they separate eventually. Colloids stay mixed for longer because the particles are so tiny. Solutions on the other hand are homogeneous mixtures held together by charges and the idea of dissolving.
What is a colloid?
A type of heterogeneous mixture, mix of two different states, but the particles cannot be easily separated since they are tiny in comparison to a suspension.
Colloids include fog and clouds (liquid particles in a gas), milk (solid particles in a liquid), and butter (solid particles in a solid). Other colloids are used industrially as catalysts. Unlike in a suspension, the particles in a colloid do not separate into two phases on standing. Keep in mind that milk will only separate into butter and liquid when it is spun so fast that the particles are forced to separate. Thus milk is a colloid because it does not turn into butter on its own.
Do not confuse a colloid with a solution. A solution is due to dissolving a solute in a solvent. A solution is a homogenous mixture that is held together with charges from ions.
What is a Solution (also known as a homogeneous mixture)?
One substance dissolved within another but it looks the same throughout.
The composition is the same throughout the mixture.
Different components are not visible.
What is a chemical reaction?
A process that occurs when substances react to create different substances or a different substance
What are some ways to preserve food?
Heating
Dehydrating
Freezing
Salting
Canning
Fermenting
Smoking
Cold storing (root cellars to store root vegetables)
What is Sterilization?
Any process that kills micro-organisms
How does freezing sterilize food?
The low temperature prevents the growth of micro-organisms that cause decay
How does salting sterilize food?
The salt draws the water out of the meat and the bacteria. The bacteria either cannot live or are inactivated without water.
How does fermentation work?
The lactobacilli creates lactic acid which is a preservative. It prevents the growth of bacteria that causes food to rot