6W1 QUESTIONS-7TH GRADE

Which of the following best describes the difference between an element and a compound?

• Elements are made of only one type of atom, while compounds are made of two or more types of atoms chemically combined.

• Elements are made of molecules, while compounds are made of atoms.

• Elements can be separated by chemical means, while compounds cannot.

• Compounds are found on the periodic table, while elements are not.

(a)   is a chemical formula for a compound.

• O
• H2O
• Fe
• N

Select the correct chemical symbol for the element sodium.

• S

• Na

• So

• Sd

Match the following chemical formulas with the number of oxygen atoms they contain.

• O₃

• 1

• CO

• 3

• CO₂

• 0

• H₂

• 2

(a)   is a physical change.

• Burning wood
• Melting ice
• Rusting iron
• Baking a cake

Which process represents a chemical change?

• Dissolving sugar in water

• Boiling water

• Digesting food

• Breaking glass

In an aqueous solution, the substance that is dissolved is called the (a)   .

• Solvent
• Solute
• Concentration
• Dilution

The concentration of a solution (a)   when more solvent is added.

• It increases
• It decreases
• It stays the same
• It becomes saturated

Match each action with its effect on the rate at which a solid solute dissolves in water.

• Lowers the rate of dissolving by reducing kinetic energy

• Decreasing the surface area

• Increases the rate of dissolving by mixing solute and solvent

• Stirring the solution

• Lowers the rate of dissolving by reducing exposed surface

• Using larger solute pieces

• Lowers the rate of dissolving by reducing contact area

• Decreasing the temperature

Crushing a sugar cube before dissolving it in water (a)   the rate of dissolution.

• It decreases the rate
• It increases the rate
• It has no effect
• It stops dissolution