Definitions
A property is observed without changing the substance
What is a physical property?
A student records that a substance has a volume of 15 mL and is cloudy in appearance. Which observation is quantitative?
Volume of 15 mL
A banana becomes sweeter as it ripens. What evidence suggests this is a chemical change even though no bubbles or colour change occur?
New substances (sugars) form.
A student dissolves sugar in water. Explain why this is not a chemical change.
No new substance forms.
A property that describes how a substance reacts to form new substances.
Chemical property
Give an example of a Qualitative and Quantitative property
Many
Is baking cookies a physical or chemical change? Explain why
Chemical: new odour
You’re at a bonfire and wood is being burnt. What type of change is occurring?
Chemical Change
A mechanic melts aluminum to reshape a car part. Another mechanic burns gasoline in an engine. Which process is chemical and why?
Burning gasoline because new substances form.
Explain a physical change
A change where no new substances are produced.
A substance is dull, rough, and opaque. What type of properties are these?
Qualitative
A reaction produces bubbles. What evidence of chemical change is observed?
Gas production
Explain why boiling is not a chemical change even though bubbles are produced
The reaction occurs without heating and produces gas.
This term refers to the shiny appearance of some metals.
What is luster?
A substance is blue, brittle, has a density of 2.3 g/mL, and melts at 90°C. Name the TWO quantitative properties.
Density and melting point
A student notices a colour change after mixing two clear liquids. Why does this suggest a chemical reaction occurred?
A new substance with different properties formed.
A candle melts while burning. Identify ONE physical change and ONE chemical change occurring.
Physical = melting wax; Chemical = burning wax
A substance changes from liquid to gas.
What is Evaporation?
A student says density is a qualitative property because you can observe it. Explain why the student is incorrect.
Density is measured and has a numerical value, making it quantitative.
A student claims bubbles formed because the liquid was boiling. Another student says a gas was produced chemically. How could you determine whether a chemical reaction actually occurred?
Look for other evidence such as temperature change, colour change, precipitate formation, or test the gas produced.
Is boiling water considered reversible? Why
Steam can condense back into liquid water.