Particle Models
Solids, liquids and gases are made up of tiny particles too small to see with the naked eye
What is matter?
The total amount of matter stays the same; matter is not created or destroyed in ordinary chemical or physical changes.
What is "conservation of matter"?
These are 2 properties you can use to identify a material
What are color and texture (also hardness, magnetism, density, conductivity).
Sugar dissolves but can be recovered by evaporating the water; no new substance is formed.
What is physical change?
Something you notice using your senses or tools. Example: "The liquid turned cloudy" or "Bubbles formed."
What is an observation?
Particles tightly packed in fixed positions and vibrate in place; they do not move freely.
What is a solid?
This tool is used to show evidence that matter in a closed system is conserved
What is a balance /scale? (to measure mass of a closed system (container + water) before and after; mass should stay the same.)
This is the property you would measure to decide if a material sinks or floats
What is density?
Paper is burned; the following evidence is observed: ash forms, release of heat and light, and new substances are produced.
What is chemical change?
Ensuring a fair test/experiment so only one factor affects the result. Example: keep starting mass or container type the same.
Why is it important to control variables in an investigation?
Particles are far apart and move freely
What is a gas?
A student mixes baking soda and vinegar in a closed container and mass stays the same to prove this known principle
What is “matter is conserved in a closed system during a chemical reaction—the total mass remains constant.”
This is how you would test for a materials conductivity
What is build a simple circuit and see if the material can light a bulb?
A colorless solution turns cloudy and gives off a gas when two clear liquids are mixed. observations: formation of a cloudy precipitate (new solid) and gas production (bubbles).
What is a chemical change?
In an investigation, I: repeat measurements, use the same containers and use the same balance for all trials.
What should you do to make sure your measurements are accurate when measuring mass for a conservation of matter experiment?
During an experiment, if you increase this variable, it will make particles move faster and often spread farther apart, which can cause a change of state.
What is temperature? Or heat
Using the same container, measure mass of container + water before and after adding salt, close to prevent evaporation, repeat trials, control temperature.
How to set up an experiment showing conservation of matter?
A material that is brittle, not stretchy, and does not conduct electricity.
What is Glass, ceramic, concrete, diamond?
I performed the following procedure on a liquid: Evaporate the liquid and check container to see if there are salt crystals observed.
How you could give evidence that mixing salt with water produced a mixture and NOT a new substance. If salt returns, it was a physical mixture (dissolution), not a new substance.
In an investigation I: Record mass values in a table and display results with a bar graph or line graph showing mass before and after; label axes and include units.
How to record and display data from an experiment that measures mass before and after heating?
Water particles stick to a sponge by attractive forces and move into the sponge's spaces; sponge pores hold water.
What is adhesion?
I perform an experiment and collected data in an open container and then repeated it in a closed container.
What is "mass may change due to gases escaping or evaporation in an open container"? To test, repeat the reaction in a sealed container and compare total mass before and after
I run the following tests and make observations: measure density, test conductivity, heat to observe boiling point or evaporation, check pH, or smell (with safety and teacher permission).
How to identify and compare two clear liquids that look the same? (or any materials that look the same)
1. Reversible physical change: given an example and evidence
2. Irreversible chemical change: give an example and evidence
1. What is freezing and melting of water?
2. What is burning wood — new substances (ash, gases) form and cannot easily be changed back?
After an investigation, I: I share results with other tables and compare procedures step-by-step, check measurement tools and units, calculate differences and percent change, look for uncontrolled variables, and repeat trials to test consistency.
How to explain why two groups found different results in the same experiments/how to find outliers.