Pure Substances
What is a pure substance?
A pure substance is a material made up of only one type of particle, which can be either an element or a compound.
What is a physical change?
A physical change is a change that affects one or more physical properties of a substance without changing its chemical composition.
What is a chemical change?
A chemical change is a process that involves a transformation of one or more substances into different substances with new chemical properties.
What does conserve matter mean?
To conserve matter means that during a chemical or physical change, the total mass of the substances involved remains constant; matter is neither created nor destroyed.
What are valence electrons?
The electrons found on the outermost shell/energy level of an atom.
What are two examples of pure substances?
Two examples of pure substances are water (H₂O) and table salt (NaCl).
What is an example of a physical change?
An example of a physical change is ice melting into water.
What happens when wood burns? (products/type of change)
A chemical change that occurs when wood burns is the formation of ash, smoke, and gases, resulting from the reaction of wood with oxygen.
Why do you know if an equation is balanced?
A balanced equation represents the conservation of matter by showing that the number of atoms of each element is the same on both sides of the equation.
True or False:
Planets are equal distances apart from each other, but are different sizes.
False, the distance between planets AND their sizes vary.
How can you identify a pure substance?
A pure substance can be identified based on its consistent physical and chemical properties, such as boiling point, melting point, and density.
How can temperature affect physical changes?
Temperature can affect physical changes by providing or removing energy, which can speed up or slow down the process (e.g., heating may speed up melting).
How can you tell if a chemical change has taken place? (list 2)
You can tell if a chemical change has occurred if there are observable signs such as color change, temperature change, gas production, or the formation of a precipitate.
What is the reason for checking to see if you have a balanced equation?
It is important to balance chemical equations to ensure that the law of conservation of matter is obeyed, meaning that all atoms must be accounted for in a reaction.
What element is in Group 3 and period 5?
In (Indium)
What is the difference between an element and a compound?
An element is a substance that cannot be broken down into simpler substances by chemical means, while a compound is made up of two or more elements that are chemically bonded together.
During a physical change, the properties of a substance may change (like shape or state), but its chemical structure remains the same.
Where to you find the reactants and products of a chemical equation?
You find the reactants on the left side and the products on the right side of the arrow.
What does a chemical equation represent?
A chemical equation represent the changes that take place in a chemical reaction.
List the planets in order starting CLOSEST to the Sun
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Describe a situation where you would have a pure substance.
A situation where you would have a pure substance is when you have distilled water, which contains only H₂O molecules.
Why is dissolving salt water a physical change?
Dissolving salt in water is a physical change because the salt retains its chemical properties and can be recovered by evaporating the water.
Why is cooking an egg a chemical change?
Cooking an egg is a chemical change because the proteins in the egg undergo a chemical reaction that changes their structure and properties.
Why is it important to have a closed system for the conservation of matter?
Conservation of matter applies to reactions in a closed system because no matter can enter or leave the system, so the total mass remains constant throughout the reaction.
Describe BOTH the geocentric model AND the heliocentric model of the universe, with telling which is accurate.
Geocentric is the model where Earth is the center of the solar system, while heliocentric is the model with the Sun in the center. The accurate model is heliocentric.