Elements & Compounds
What is the smallest unit of an element that still has the properties of that element?
→ What is an atom?
Melting ice is an example of what type of change?
What is a physical change?
In a solution of sugar water, which is the solute?
→ What is sugar?
Name one factor that can speed up how quickly something dissolves in water.
→ Increasing temperature, stirring, or crushing the solute.
What does it mean if a solution is “concentrated”?
→ It has a lot of solute compared to solvent.
True or False: All molecules are compounds.
What is False
Which type of change creates a new substance: physical or chemical?
What is a chemical change?
In a saltwater solution, which is the solvent?
→ What is water?
How does increasing temperature usually affect dissolving rate?
→ It makes solutes dissolve faster.
What does it mean if a solution is “diluted”?
→ It has more solvent compared to solute (weaker solution).
Give one example of an element and one example of a compound.
Element: Oxygen (O₂); Compound: Water (H₂O).
Bubbles forming when baking soda reacts with vinegar is evidence of what?
What is a chemical change?
What is the difference between a heterogeneous mixture and a homogeneous mixture?
→ Heterogeneous = unevenly mixed; Homogeneous = evenly mixed.
Why does stirring a solution help a solute dissolve faster?
→ It spreads the particles and increases collisions.
If two solutions contain the same amount of solute but one has more water, which is more diluted?
→ The one with more water.
What does a chemical formula tell us about a substance?
The types of elements and how many atoms of each.
List two signs that a chemical change has occurred.
Gas production, color change, temperature change, or formation of a new substance.
True or False: All solutions are mixtures, but not all mixtures are solutions.
→ What is True?
Why do crushed tablets dissolve faster than whole tablets?
→ Because they have more surface area exposed.
A student dissolves 10g of salt in 100mL of water. Another dissolves 10g of salt in 200mL of water. Which solution is more concentrated?
→ The 10g/100mL solution.
Which has more than one type of atom: an element or a compound?
What is a compound?
Why is dissolving salt in water usually considered a physical change?
Because no new substance forms; the salt can be recovered.
Give an everyday example of a solution and an everyday example of a mixture.
→ Solution: sweet tea. Mixture: salad.
List three ways you could make sugar dissolve faster in iced tea.
→ Stirring, increasing temperature, crushing the sugar.
How can you make a solution less concentrated without removing solute?
→ Add more solvent.