Matter Models
What is the smallest unit of an element that still retains the properties of that element?
An atom
Name one observable sign that a chemical reaction might have occurred when two substances are mixed.
Observable signs like gas bubbles, temperature change, color change, or solid formation provide evidence a chemical reaction may have occurred.
What is a synthetic material? Give one example students commonly encounter.
A synthetic material is human-made using natural resources.
Example: plastic made from petroleum.
State the law that describes how mass behaves in a typical chemical reaction.
The Law of Conservation of Mass: The number of atoms stays the same in a chemical reaction, so mass does not change.
Define an exothermic reaction and give one simple classroom example.
An exothermic reaction releases thermal energy.
Example: hand warmers showing temperature increase.
Draw or describe a simple model showing how two hydrogen atoms and one oxygen atom bond to form a water molecule. Name the type of bond that holds the atoms together.
A water molecule model shows two hydrogen atoms bonded to one oxygen atom in an H–O–H arrangement.
You mix baking soda and vinegar. What gas is produced and how could you show that gas is being formed?
Baking soda + vinegar produces carbon dioxide gas.
Collecting bubbles in a balloon
Name a natural resource that is used to make a common synthetic material, and name the synthetic product made from it.
Natural resource: petroleum
Synthetic product: nylon, polyester, or plastics
If you start with 10 g10 g of reactant A and 15 g15 g of reactant B in a closed container and they react completely, what total mass of products should you expect? Explain.
10 g + 15 g → 25 g total
A model of atoms before and after shows all atoms are still present → mass unchanged.
Define an endothermic reaction and give one simple classroom example.
An endothermic reaction absorbs thermal energy.
Example: instant cold packs becoming colder when activated.
This type of structure is modeled as a repeating, ordered pattern of atoms or ions—like those found in table salt crystals.
an extended structure (or a crystal lattice)?
A student records temperature, color change, and formation of a solid when mixing two solutions. Which of these observations are evidence of a chemical reaction, and why?
Temperature change, color change, and formation of a solid all show new substances may have formed.
These data indicate a chemical reaction occurred.
Explain one way synthetic materials benefit society and one possible negative impact they can have on the environment.
Benefit: durable products used in medicine, clothing, and technology
Negative impact: wastes and pollution can harm environments
You are given data showing mass before mixing two reactants and mass after reaction in a closed system. The masses are the same. Explain how this supports the Law of Conservation of Mass.
Equal mass before and after in a closed system shows atoms were rearranged. Which follows the Law of Conservation of Mass stating matter cannot be created or destroyed in a chemical reaction or physical change; it only changes form, meaning the total mass of reactants always equals the total mass of products in a closed system
A student builds a device that uses a chemical reaction to produce heat when activated. Name two safety considerations they must include in their design plan.
Safety considerations for a heat-producing device:
Prevent burns — insulated container
Use proper safety equipment (goggles/gloves)
Explain the difference between a molecule and an extended structure (like a crystal). Give one example of each.
A molecule is a model of only a few atoms bonded together (Example: CO₂)
• An extended structure model shows a repeating pattern of many atoms or ions (Example: salt crystal – Na⁺ and Cl⁻ in a lattice)
xplain how the production of light during a reaction is evidence of a chemical change. Give an example of a reaction that produces light.
Light production means energy is released differently because new substances formed.
Example: glow sticks releasing light during a reaction.
Propose a short class investigation to compare a natural material and a synthetic material used for clothing. What data would you collect and how would it show differences in properties and impacts?
Investigation: Compare cotton (natural) vs. polyester (synthetic)
Data to collect:
Absorbency
Strength/stretch
Environmental breakdown
When a reaction makes a gas but the total mass goes down because the container was open, this is the reason the mass didn’t actually disappear.
the gas escaped the system / the system was not closed
This measurement tool would be used to collect data showing that an exothermic reaction releases heat.
a thermometer