Elements, compounds and mixtures

Answer Key - Grade 10 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Ari splits 18 g of pure water into 2 g of hydrogen and 16 g of oxygen. How many grams of oxygen are in 63 g of pure water?

   56 g
2. 2.

   Bo splits 11 g of pure carbon dioxide into 3 g of carbon and 8 g of oxygen. How many grams of oxygen are in 33 g of pure carbon dioxide?

   24 g
3. 3.

   Esme splits 5 g of pure magnesium oxide into 3 g of magnesium and 2 g of oxygen. How many grams of oxygen are in 20 g of pure magnesium oxide?

   8 g
5. 4.

   Which box shows a pure compound, Jun?

   • Box A
   • Box D
   • Box C
6. 5.

   Which box is a mixture of an element and a compound, Luz?

   Use the picture in question 4.

   • Box B
   • Box D
   • Box C

7. Read this first

   Boiling of four clear liquids at 1 atm (example data)

   sample	starts boiling (°C)	stops boiling (°C)
   P	78.4	78.4
   Q	78.4	91.0
   R	100.0	100.0
   S	100.6	104.0

8. 6.

   Which two samples look like pure substances, Milo?

   • P and Q: each starts boiling at 78.4 °C and keeps going
   • P and R: each boils at one steady temperature
   • R and S: each boils at nearly 100 °C, close to water
9. 7.

   Ethanol boils at 78.4 °C. Sample Q boils from 78.4 to 91.0 °C. What does this suggest about Q, Pia?

   • It is a compound that boils in two steps
   • It is pure ethanol, because boiling began at the temperature of ethanol
   • It holds ethanol plus at least one liquid that boils higher

10. Three solids in a mix (real properties)

    solid	dissolves in water	attracted to a magnet
    iron filings	no	yes
    sand	no	no
    table salt	yes	no

11. 8.

    Sand, salt and iron filings are mixed dry. Which first step lifts one solid out without adding anything, Ren?

    • Filter the dry mixture through paper to catch the sand
    • Heat the mixture until the salt melts away from the others
    • Pass a magnet over it to lift out the iron filings
12. 9.

    The iron is out. Sand and salt are stirred into water and poured through filter paper. What stays on the paper, Tala?

    • Both solids: the salt crystals are too big to pass through the paper
    • Nothing: both solids dissolve in water
    • The sand: salt dissolves into tiny ions that pass through with the water
13. 10.

    The salt solution passed through the filter. How can the salt be recovered, Zee?

    • Evaporate the water; the salt stays behind as crystals
    • Add more sand so the salt sticks to the sand
    • Filter it again, because salt is a solid in the water