Compounds and Elements
This pure substance is made of only one kind of atom, like gold (Au) or oxygen (O₂).
What is an element?
In 3NaCl, how many total atoms are there?
What is 6?
Milk left out on the counter smells sour. What evidence of chemical change is this
What is an odor change?
A student stirs cocoa powder into hot milk. Identify solute and solvent.
What is cocoa powder = solute; milk = solvent?
A student makes Kool-Aid but forgets to stir. It takes longer to dissolve. Which factor was missing?
What is stirring/agitation?
Table sugar (C₁₂H₂₂O₁₁) is this type of substance because it’s made of many different atoms bonded together.
What is a compound?
In 4H₂O, how many hydrogen atoms are there?
What is 8?
Mixing two clear liquids creates a yellow solid that sinks. What’s the evidence of chemical change
What is precipitate formation?
You have a strong iced tea and add 2 more cups of water. What happens to the concentration level and why?
What is it becomes weaker because it was diluted.
A student stirs salt into warm water. Which two factors are helping the salt dissolve faster?
What is stirring and temperature?
H₂ – is it an element or a compound?
What is an element?
2Al₂(SO₄)₃, how many oxygen atoms are there?
What is 24?
A can of soda freezes and bursts open in the freezer. Physical or chemical?
What is a physical change?
Two saltwater samples are compared. Sample A tastes salty, Sample B tastes watery. Which has higher concentration?
What is Sample A (because it has more solute)
You want cocoa powder to dissolve faster in milk. Name two things you could do.
What is heat the milk and stir it (increase temperature and agitation)?
CO – is it an element or a compound?
What is a compound?
In 3Ca(OH)₂, how many total oxygen atoms are there?
What is 6?
Butter melts on hot pancakes. Physical or chemical?
What is a physical change?
Two cups of Kool-Aid are compared: Cup A (1 scoop powder, 1 cup water) and Cup B (2 scoops powder, 1 cup water). Which cup is more concentrated and why?
What is Cup B; more solute per solvent = higher concentration.
A sugar cube dissolves slowly in iced tea. What three things could the student do to make it dissolve faster?
What is use smaller sugar pieces, stir, and heat the tea.
O₃ , also known as ozone, protects us from harmful rays. Is it an element or a compound?
What is an element? (because it only has one type of atom, oxygen)
In 4Mg(OH)₂, how many total atoms are there?
What is 20?
Cooking an egg turns the clear egg white solid and white. Which evidence of chemical change is this?
What is a new substance OR color change?
Salt dissolves in water. Identify solute, solvent, and describe if the mixture is concentrated or dilute if very little salt is added.
What is solute = salt, solvent = water, diluted solution with low concentration.
Ice-cold lemonade doesn’t taste sweet until stirred. Is this about temperature, stirring, or both?
What is both (low temperature slows dissolving, stirring speeds it up)?